| Message ID | 20211217233015.67664-2-sean.anderson@seco.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v12,1/2] dt-bindings: pwm: Add Xilinx AXI Timer | expand |
On 12/17/21 6:30 PM, Sean Anderson wrote: > This adds PWM support for Xilinx LogiCORE IP AXI soft timers commonly > found on Xilinx FPGAs. At the moment clock control is very basic: we > just enable the clock during probe and pin the frequency. In the future, > someone could add support for disabling the clock when not in use. > > Some common code has been specially demarcated. While currently only > used by the PWM driver, it is anticipated that it may be split off in > the future to be used by the timer driver as well. > > This driver was written with reference to Xilinx DS764 for v1.03.a [1]. > > [1] https://www.xilinx.com/support/documentation/ip_documentation/axi_timer/v1_03_a/axi_timer_ds764.pdf > > Signed-off-by: Sean Anderson <sean.anderson@seco.com> > Acked-by: Michal Simek <michal.simek@xilinx.com> > --- > > Changes in v12: > - Add a comment to the timer driver about #pwm-cells > - Combine/expand comments on rounding in xilinx_pwm_apply > > Changes in v11: > - Add comment about why we test for #pwm-cells > - Clarify comment on generate out signal > - Rename pwm variables to xilinx_pwm > - Round like Uwe wants... > - s/xilinx_timer/xilinx_pwm/ for non-common functions > > Changes in v10: > - Fix compilation error in timer driver > > Changes in v9: > - Refactor "if { return } else if { }" to "if { return } if { }" > - Remove drivers/clocksource/timer-xilinx-common.c from MAINTAINERS > - Remove xilinx_timer_common_init and integrate it into xilinx_timer_probe > > Changes in v8: > - Drop new timer driver; it has been deferred for future series > > Changes in v7: > - Add dependency on OF_ADDRESS > - Fix period_cycles calculation > - Fix typo in limitations > > Changes in v6: > - Capitalize error messages > - Don't disable regmap locking to allow inspection of registers via > debugfs > - Prevent overflow when calculating period_cycles > - Remove enabled variable from xilinx_pwm_apply > - Swap order of period_cycle range comparisons > > Changes in v5: > - Allow non-zero #pwm-cells > - Correctly set duty_cycle in get_state when TLR0=TLR1 > - Elaborate on limitation section > - Perform some additional checks/rounding in apply_state > - Remove xlnx,axi-timer-2.0 compatible string > - Rework duty-cycle and period calculations with feedback from Uwe > - Switch to regmap to abstract endianness issues > - Use more verbose error messages > > Changes in v4: > - Don't use volatile in read/write replacements. Some arches have it and > some don't. > - Put common timer properties into their own struct to better reuse > code. > - Remove references to properties which are not good enough for Linux. > > Changes in v3: > - Add clockevent and clocksource support > - Remove old microblaze driver > - Rewrite probe to only use a device_node, since timers may need to be > initialized before we have proper devices. This does bloat the code a bit > since we can no longer rely on helpers such as dev_err_probe. We also > cannot rely on device resources being free'd on failure, so we must free > them manually. > - We now access registers through xilinx_timer_(read|write). This allows us > to deal with endianness issues, as originally seen in the microblaze > driver. CAVEAT EMPTOR: I have not tested this on big-endian! > > Changes in v2: > - Add comment describing device > - Add comment explaining why we depend on !MICROBLAZE > - Add dependencies on COMMON_CLK and HAS_IOMEM > - Cast dividends to u64 to avoid overflow > - Check for over- and underflow when calculating TLR > - Check range of xlnx,count-width > - Don't compile this module by default for arm64 > - Don't set pwmchip.base to -1 > - Ensure the clock is always running when the pwm is registered > - Remove debugfs file :l > - Rename TCSR_(SET|CLEAR) to TCSR_RUN_(SET|CLEAR) > - Report errors with dev_error_probe > - Set xilinx_pwm_ops.owner > - Use NSEC_TO_SEC instead of defining our own > - Use TCSR_RUN_MASK to check if the PWM is enabled, as suggested by Uwe > > MAINTAINERS | 6 + > arch/microblaze/kernel/timer.c | 4 + > drivers/pwm/Kconfig | 14 ++ > drivers/pwm/Makefile | 1 + > drivers/pwm/pwm-xilinx.c | 319 +++++++++++++++++++++++++++++ > include/clocksource/timer-xilinx.h | 91 ++++++++ > 6 files changed, 435 insertions(+) > create mode 100644 drivers/pwm/pwm-xilinx.c > create mode 100644 include/clocksource/timer-xilinx.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index 13f9a84a617e..373757fcc8c6 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -20925,6 +20925,12 @@ F: drivers/misc/Makefile > F: drivers/misc/xilinx_sdfec.c > F: include/uapi/misc/xilinx_sdfec.h > > +XILINX PWM DRIVER > +M: Sean Anderson <sean.anderson@seco.com> > +S: Maintained > +F: drivers/pwm/pwm-xilinx.c > +F: include/clocksource/timer-xilinx.h > + > XILINX UARTLITE SERIAL DRIVER > M: Peter Korsgaard <jacmet@sunsite.dk> > L: linux-serial@vger.kernel.org > diff --git a/arch/microblaze/kernel/timer.c b/arch/microblaze/kernel/timer.c > index f8832cf49384..26c385582c3b 100644 > --- a/arch/microblaze/kernel/timer.c > +++ b/arch/microblaze/kernel/timer.c > @@ -251,6 +251,10 @@ static int __init xilinx_timer_init(struct device_node *timer) > u32 timer_num = 1; > int ret; > > + /* If this property is present, the device is a PWM and not a timer */ > + if (of_property_read_bool(timer, "#pwm-cells")) > + return 0; > + > if (initialized) > return -EINVAL; > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > index 21e3b05a5153..cefbf00b4c7e 100644 > --- a/drivers/pwm/Kconfig > +++ b/drivers/pwm/Kconfig > @@ -640,4 +640,18 @@ config PWM_VT8500 > To compile this driver as a module, choose M here: the module > will be called pwm-vt8500. > > +config PWM_XILINX > + tristate "Xilinx AXI Timer PWM support" > + depends on OF_ADDRESS > + depends on COMMON_CLK > + select REGMAP_MMIO > + help > + PWM driver for Xilinx LogiCORE IP AXI timers. This timer is > + typically a soft core which may be present in Xilinx FPGAs. > + This device may also be present in Microblaze soft processors. > + If you don't have this IP in your design, choose N. > + > + To compile this driver as a module, choose M here: the module > + will be called pwm-xilinx. > + > endif > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > index 708840b7fba8..ea785480359b 100644 > --- a/drivers/pwm/Makefile > +++ b/drivers/pwm/Makefile > @@ -60,3 +60,4 @@ obj-$(CONFIG_PWM_TWL) += pwm-twl.o > obj-$(CONFIG_PWM_TWL_LED) += pwm-twl-led.o > obj-$(CONFIG_PWM_VISCONTI) += pwm-visconti.o > obj-$(CONFIG_PWM_VT8500) += pwm-vt8500.o > +obj-$(CONFIG_PWM_XILINX) += pwm-xilinx.o > diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c > new file mode 100644 > index 000000000000..b4d93e8812c6 > --- /dev/null > +++ b/drivers/pwm/pwm-xilinx.c > @@ -0,0 +1,319 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> > + * > + * Limitations: > + * - When changing both duty cycle and period, we may end up with one cycle > + * with the old duty cycle and the new period. This is because the counters > + * may only be reloaded by first stopping them, or by letting them be > + * automatically reloaded at the end of a cycle. If this automatic reload > + * happens after we set TLR0 but before we set TLR1 then we will have a > + * bad cycle. This could probably be fixed by reading TCR0 just before > + * reprogramming, but I think it would add complexity for little gain. > + * - Cannot produce 100% duty cycle by configuring the TLRs. This might be > + * possible by stopping the counters at an appropriate point in the cycle, > + * but this is not (yet) implemented. > + * - Only produces "normal" output. > + * - Always produces low output if disabled. > + */ > + > +#include <clocksource/timer-xilinx.h> > +#include <linux/clk.h> > +#include <linux/clk-provider.h> > +#include <linux/device.h> > +#include <linux/module.h> > +#include <linux/of.h> > +#include <linux/platform_device.h> > +#include <linux/pwm.h> > +#include <linux/regmap.h> > + > +/* > + * The following functions are "common" to drivers for this device, and may be > + * exported at a future date. > + */ > +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, > + u64 cycles) > +{ > + WARN_ON(cycles < 2 || cycles - 2 > priv->max); > + > + if (tcsr & TCSR_UDT) > + return cycles - 2; > + return priv->max - cycles + 2; > +} > + > +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, > + u32 tlr, u32 tcsr) > +{ > + u64 cycles; > + > + if (tcsr & TCSR_UDT) > + cycles = tlr + 2; > + else > + cycles = (u64)priv->max - tlr + 2; > + > + /* cycles has a max of 2^32 + 2 */ > + return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC, > + clk_get_rate(priv->clk)); > +} > + > +/* > + * The idea here is to capture whether the PWM is actually running (e.g. > + * because we or the bootloader set it up) and we need to be careful to ensure > + * we don't cause a glitch. According to the data sheet, to enable the PWM we > + * need to > + * > + * - Set both timers to generate mode (MDT=1) > + * - Set both timers to PWM mode (PWMA=1) > + * - Enable the generate out signals (GENT=1) > + * > + * In addition, > + * > + * - The timer must be running (ENT=1) > + * - The timer must auto-reload TLR into TCR (ARHT=1) > + * - We must not be in the process of loading TLR into TCR (LOAD=0) > + * - Cascade mode must be disabled (CASC=0) > + * > + * If any of these differ from usual, then the PWM is either disabled, or is > + * running in a mode that this driver does not support. > + */ > +#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA) > +#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD) > +#define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR) > + > +struct xilinx_pwm_device { > + struct pwm_chip chip; > + struct xilinx_timer_priv priv; > +}; > + > +static inline struct xilinx_timer_priv > +*xilinx_pwm_chip_to_priv(struct pwm_chip *chip) > +{ > + return &container_of(chip, struct xilinx_pwm_device, chip)->priv; > +} > + > +static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1) > +{ > + return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET && > + (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET; > +} > + > +static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused, > + const struct pwm_state *state) > +{ > + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); > + u32 tlr0, tlr1, tcsr0, tcsr1; > + u64 period_cycles, duty_cycles; > + unsigned long rate; > + > + if (state->polarity != PWM_POLARITY_NORMAL) > + return -EINVAL; > + > + /* > + * To be representable by TLR, cycles must be between 2 and > + * priv->max + 2. To enforce this we can reduce the cycles, but we may > + * not increase them. Caveat emptor: while this does result in more > + * predictable rounding, it may also result in a completely different > + * duty cycle (% high time) than what was requested. > + */ > + rate = clk_get_rate(priv->clk); > + /* Avoid overflow */ > + period_cycles = min_t(u64, state->period, ULONG_MAX * NSEC_PER_SEC); > + period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC); > + period_cycles = min_t(u64, period_cycles, priv->max + 2); > + if (period_cycles < 2) > + return -ERANGE; > + > + /* Same thing for duty cycles */ > + duty_cycles = min_t(u64, state->duty_cycle, ULONG_MAX * NSEC_PER_SEC); > + duty_cycles = mul_u64_u32_div(duty_cycles, rate, NSEC_PER_SEC); > + duty_cycles = min_t(u64, duty_cycles, priv->max + 2); > + > + /* > + * If we specify 100% duty cycle, we will get 0% instead, so decrease > + * the duty cycle count by one. > + */ > + if (duty_cycles >= period_cycles) > + duty_cycles = period_cycles - 1; > + > + /* Round down to 0% duty cycle for unrepresentable duty cycles */ > + if (duty_cycles < 2) > + duty_cycles = period_cycles; > + > + regmap_read(priv->map, TCSR0, &tcsr0); > + regmap_read(priv->map, TCSR1, &tcsr1); > + tlr0 = xilinx_timer_tlr_cycles(priv, tcsr0, period_cycles); > + tlr1 = xilinx_timer_tlr_cycles(priv, tcsr1, duty_cycles); > + regmap_write(priv->map, TLR0, tlr0); > + regmap_write(priv->map, TLR1, tlr1); > + > + if (state->enabled) { > + /* > + * If the PWM is already running, then the counters will be > + * reloaded at the end of the current cycle. > + */ > + if (!xilinx_timer_pwm_enabled(tcsr0, tcsr1)) { > + /* Load TLR into TCR */ > + regmap_write(priv->map, TCSR0, tcsr0 | TCSR_LOAD); > + regmap_write(priv->map, TCSR1, tcsr1 | TCSR_LOAD); > + /* Enable timers all at once with ENALL */ > + tcsr0 = (TCSR_PWM_SET & ~TCSR_ENT) | (tcsr0 & TCSR_UDT); > + tcsr1 = TCSR_PWM_SET | TCSR_ENALL | (tcsr1 & TCSR_UDT); > + regmap_write(priv->map, TCSR0, tcsr0); > + regmap_write(priv->map, TCSR1, tcsr1); > + } > + } else { > + regmap_write(priv->map, TCSR0, 0); > + regmap_write(priv->map, TCSR1, 0); > + } > + > + return 0; > +} > + > +static void xilinx_pwm_get_state(struct pwm_chip *chip, > + struct pwm_device *unused, > + struct pwm_state *state) > +{ > + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); > + u32 tlr0, tlr1, tcsr0, tcsr1; > + > + regmap_read(priv->map, TLR0, &tlr0); > + regmap_read(priv->map, TLR1, &tlr1); > + regmap_read(priv->map, TCSR0, &tcsr0); > + regmap_read(priv->map, TCSR1, &tcsr1); > + state->period = xilinx_timer_get_period(priv, tlr0, tcsr0); > + state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1); > + state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1); > + state->polarity = PWM_POLARITY_NORMAL; > + > + /* 100% duty cycle results in constant low output */ > + if (state->period == state->duty_cycle) > + state->duty_cycle = 0; > +} > + > +static const struct pwm_ops xilinx_pwm_ops = { > + .apply = xilinx_pwm_apply, > + .get_state = xilinx_pwm_get_state, > + .owner = THIS_MODULE, > +}; > + > +static const struct regmap_config xilinx_pwm_regmap_config = { > + .reg_bits = 32, > + .reg_stride = 4, > + .val_bits = 32, > + .val_format_endian = REGMAP_ENDIAN_LITTLE, > + .max_register = TCR1, > +}; > + > +static int xilinx_pwm_probe(struct platform_device *pdev) > +{ > + int ret; > + struct device *dev = &pdev->dev; > + struct device_node *np = dev->of_node; > + struct xilinx_timer_priv *priv; > + struct xilinx_pwm_device *xilinx_pwm; > + u32 pwm_cells, one_timer, width; > + void __iomem *regs; > + > + /* If there are no PWM cells, this binding is for a timer */ > + ret = of_property_read_u32(np, "#pwm-cells", &pwm_cells); > + if (ret == -EINVAL) > + return -ENODEV; > + if (ret) > + return dev_err_probe(dev, ret, "could not read #pwm-cells\n"); > + > + xilinx_pwm = devm_kzalloc(dev, sizeof(*xilinx_pwm), GFP_KERNEL); > + if (!xilinx_pwm) > + return -ENOMEM; > + platform_set_drvdata(pdev, xilinx_pwm); > + priv = &xilinx_pwm->priv; > + > + regs = devm_platform_ioremap_resource(pdev, 0); > + if (IS_ERR(regs)) > + return PTR_ERR(regs); > + > + priv->map = devm_regmap_init_mmio(dev, regs, > + &xilinx_pwm_regmap_config); > + if (IS_ERR(priv->map)) > + return dev_err_probe(dev, PTR_ERR(priv->map), > + "Could not create regmap\n"); > + > + ret = of_property_read_u32(np, "xlnx,one-timer-only", &one_timer); > + if (ret) > + return dev_err_probe(dev, ret, > + "Could not read xlnx,one-timer-only\n"); > + > + if (one_timer) > + return dev_err_probe(dev, -EINVAL, > + "Two timers required for PWM mode\n"); > + > + > + ret = of_property_read_u32(np, "xlnx,count-width", &width); > + if (ret == -EINVAL) > + width = 32; > + else if (ret) > + return dev_err_probe(dev, ret, > + "Could not read xlnx,count-width\n"); > + > + if (width != 8 && width != 16 && width != 32) > + return dev_err_probe(dev, -EINVAL, > + "Invalid counter width %d\n", width); > + priv->max = BIT_ULL(width) - 1; > + > + /* > + * The polarity of the Generate Out signals must be active high for PWM > + * mode to work. We could determine this from the device tree, but > + * alas, such properties are not allowed to be used. > + */ > + > + priv->clk = devm_clk_get(dev, "s_axi_aclk"); > + if (IS_ERR(priv->clk)) > + return dev_err_probe(dev, PTR_ERR(priv->clk), > + "Could not get clock\n"); > + > + ret = clk_prepare_enable(priv->clk); > + if (ret) > + return dev_err_probe(dev, ret, "Clock enable failed\n"); > + clk_rate_exclusive_get(priv->clk); > + > + xilinx_pwm->chip.dev = dev; > + xilinx_pwm->chip.ops = &xilinx_pwm_ops; > + xilinx_pwm->chip.npwm = 1; > + ret = pwmchip_add(&xilinx_pwm->chip); > + if (ret) { > + clk_rate_exclusive_put(priv->clk); > + clk_disable_unprepare(priv->clk); > + return dev_err_probe(dev, ret, "Could not register PWM chip\n"); > + } > + > + return 0; > +} > + > +static int xilinx_pwm_remove(struct platform_device *pdev) > +{ > + struct xilinx_pwm_device *xilinx_pwm = platform_get_drvdata(pdev); > + > + pwmchip_remove(&xilinx_pwm->chip); > + clk_rate_exclusive_put(xilinx_pwm->priv.clk); > + clk_disable_unprepare(xilinx_pwm->priv.clk); > + return 0; > +} > + > +static const struct of_device_id xilinx_pwm_of_match[] = { > + { .compatible = "xlnx,xps-timer-1.00.a", }, > + {}, > +}; > +MODULE_DEVICE_TABLE(of, xilinx_pwm_of_match); > + > +static struct platform_driver xilinx_pwm_driver = { > + .probe = xilinx_pwm_probe, > + .remove = xilinx_pwm_remove, > + .driver = { > + .name = "xilinx-pwm", > + .of_match_table = of_match_ptr(xilinx_pwm_of_match), > + }, > +}; > +module_platform_driver(xilinx_pwm_driver); > + > +MODULE_ALIAS("platform:xilinx-pwm"); > +MODULE_DESCRIPTION("PWM driver for Xilinx LogiCORE IP AXI Timer"); > +MODULE_LICENSE("GPL v2"); > diff --git a/include/clocksource/timer-xilinx.h b/include/clocksource/timer-xilinx.h > new file mode 100644 > index 000000000000..1f7757b84a5e > --- /dev/null > +++ b/include/clocksource/timer-xilinx.h > @@ -0,0 +1,91 @@ > +/* SPDX-License-Identifier: GPL-2.0+ */ > +/* > + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> > + */ > + > +#ifndef XILINX_TIMER_H > +#define XILINX_TIMER_H > + > +#include <linux/compiler.h> > + > +#define TCSR0 0x00 > +#define TLR0 0x04 > +#define TCR0 0x08 > +#define TCSR1 0x10 > +#define TLR1 0x14 > +#define TCR1 0x18 > + > +#define TCSR_MDT BIT(0) > +#define TCSR_UDT BIT(1) > +#define TCSR_GENT BIT(2) > +#define TCSR_CAPT BIT(3) > +#define TCSR_ARHT BIT(4) > +#define TCSR_LOAD BIT(5) > +#define TCSR_ENIT BIT(6) > +#define TCSR_ENT BIT(7) > +#define TCSR_TINT BIT(8) > +#define TCSR_PWMA BIT(9) > +#define TCSR_ENALL BIT(10) > +#define TCSR_CASC BIT(11) > + > +struct clk; > +struct device_node; > +struct regmap; > + > +/** > + * struct xilinx_timer_priv - Private data for Xilinx AXI timer drivers > + * @map: Regmap of the device, possibly with an offset > + * @clk: Parent clock > + * @max: Maximum value of the counters > + */ > +struct xilinx_timer_priv { > + struct regmap *map; > + struct clk *clk; > + u32 max; > +}; > + > +/** > + * xilinx_timer_tlr_cycles() - Calculate the TLR for a period specified > + * in clock cycles > + * @priv: The timer's private data > + * @tcsr: The value of the TCSR register for this counter > + * @cycles: The number of cycles in this period > + * > + * Callers of this function MUST ensure that @cycles is representable as > + * a TLR. > + * > + * Return: The calculated value for TLR > + */ > +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, > + u64 cycles); > + > +/** > + * xilinx_timer_get_period() - Get the current period of a counter > + * @priv: The timer's private data > + * @tlr: The value of TLR for this counter > + * @tcsr: The value of TCSR for this counter > + * > + * Return: The period, in ns > + */ > +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, > + u32 tlr, u32 tcsr); > + > +/** > + * xilinx_timer_common_init() - Perform common initialization for Xilinx > + * AXI timer drivers. > + * @priv: The timer's private data > + * @np: The devicetree node for the timer > + * @one_timer: Set to %1 if there is only one timer > + * > + * This performs common initialization, such as detecting endianness, > + * and parsing devicetree properties. @priv->regs must be initialized > + * before calling this function. This function initializes @priv->read, > + * @priv->write, and @priv->width. > + * > + * Return: 0, or negative errno > + */ > +int xilinx_timer_common_init(struct device_node *np, > + struct xilinx_timer_priv *priv, > + u32 *one_timer); > + > +#endif /* XILINX_TIMER_H */ > ping? Uwe/Thierry, can you have a look at this? --Sean
Hello, first of all: Sorry for taking so long for the next review round. > diff --git a/arch/microblaze/kernel/timer.c b/arch/microblaze/kernel/timer.c > index f8832cf49384..26c385582c3b 100644 > --- a/arch/microblaze/kernel/timer.c > +++ b/arch/microblaze/kernel/timer.c > @@ -251,6 +251,10 @@ static int __init xilinx_timer_init(struct device_node *timer) > u32 timer_num = 1; > int ret; > > + /* If this property is present, the device is a PWM and not a timer */ > + if (of_property_read_bool(timer, "#pwm-cells")) > + return 0; > + > if (initialized) > return -EINVAL; > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > index 21e3b05a5153..cefbf00b4c7e 100644 > --- a/drivers/pwm/Kconfig > +++ b/drivers/pwm/Kconfig > @@ -640,4 +640,18 @@ config PWM_VT8500 > To compile this driver as a module, choose M here: the module > will be called pwm-vt8500. > > +config PWM_XILINX > + tristate "Xilinx AXI Timer PWM support" > + depends on OF_ADDRESS > + depends on COMMON_CLK > + select REGMAP_MMIO > + help > + PWM driver for Xilinx LogiCORE IP AXI timers. This timer is > + typically a soft core which may be present in Xilinx FPGAs. > + This device may also be present in Microblaze soft processors. > + If you don't have this IP in your design, choose N. > + > + To compile this driver as a module, choose M here: the module > + will be called pwm-xilinx. > + > endif > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > index 708840b7fba8..ea785480359b 100644 > --- a/drivers/pwm/Makefile > +++ b/drivers/pwm/Makefile > @@ -60,3 +60,4 @@ obj-$(CONFIG_PWM_TWL) += pwm-twl.o > obj-$(CONFIG_PWM_TWL_LED) += pwm-twl-led.o > obj-$(CONFIG_PWM_VISCONTI) += pwm-visconti.o > obj-$(CONFIG_PWM_VT8500) += pwm-vt8500.o > +obj-$(CONFIG_PWM_XILINX) += pwm-xilinx.o > diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c > new file mode 100644 > index 000000000000..b4d93e8812c6 > --- /dev/null > +++ b/drivers/pwm/pwm-xilinx.c > @@ -0,0 +1,319 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> > + * > + * Limitations: > + * - When changing both duty cycle and period, we may end up with one cycle > + * with the old duty cycle and the new period. This is because the counters > + * may only be reloaded by first stopping them, or by letting them be > + * automatically reloaded at the end of a cycle. If this automatic reload > + * happens after we set TLR0 but before we set TLR1 then we will have a > + * bad cycle. This could probably be fixed by reading TCR0 just before > + * reprogramming, but I think it would add complexity for little gain. > + * - Cannot produce 100% duty cycle by configuring the TLRs. This might be > + * possible by stopping the counters at an appropriate point in the cycle, > + * but this is not (yet) implemented. > + * - Only produces "normal" output. > + * - Always produces low output if disabled. > + */ > + > +#include <clocksource/timer-xilinx.h> > +#include <linux/clk.h> > +#include <linux/clk-provider.h> > +#include <linux/device.h> > +#include <linux/module.h> > +#include <linux/of.h> > +#include <linux/platform_device.h> > +#include <linux/pwm.h> > +#include <linux/regmap.h> > + > +/* > + * The following functions are "common" to drivers for this device, and may be > + * exported at a future date. > + */ > +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, > + u64 cycles) > +{ > + WARN_ON(cycles < 2 || cycles - 2 > priv->max); > + > + if (tcsr & TCSR_UDT) > + return cycles - 2; > + return priv->max - cycles + 2; > +} > + > +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, > + u32 tlr, u32 tcsr) > +{ > + u64 cycles; > + > + if (tcsr & TCSR_UDT) > + cycles = tlr + 2; > + else > + cycles = (u64)priv->max - tlr + 2; > + > + /* cycles has a max of 2^32 + 2 */ If you add "... so the multiplication doesn't overflow." it becomes more obvious why this comment is there. > + return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC, > + clk_get_rate(priv->clk)); > +} > + > +/* > + * The idea here is to capture whether the PWM is actually running (e.g. > + * because we or the bootloader set it up) and we need to be careful to ensure > + * we don't cause a glitch. According to the data sheet, to enable the PWM we > + * need to > + * > + * - Set both timers to generate mode (MDT=1) > + * - Set both timers to PWM mode (PWMA=1) > + * - Enable the generate out signals (GENT=1) > + * > + * In addition, > + * > + * - The timer must be running (ENT=1) > + * - The timer must auto-reload TLR into TCR (ARHT=1) > + * - We must not be in the process of loading TLR into TCR (LOAD=0) > + * - Cascade mode must be disabled (CASC=0) > + * > + * If any of these differ from usual, then the PWM is either disabled, or is > + * running in a mode that this driver does not support. > + */ > +#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA) > +#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD) > +#define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR) > + > +struct xilinx_pwm_device { > + struct pwm_chip chip; > + struct xilinx_timer_priv priv; > +}; > + > +static inline struct xilinx_timer_priv > +*xilinx_pwm_chip_to_priv(struct pwm_chip *chip) > +{ > + return &container_of(chip, struct xilinx_pwm_device, chip)->priv; > +} > + > +static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1) > +{ > + return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET && > + (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET; > +} > + > +static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused, > + const struct pwm_state *state) > +{ > + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); > + u32 tlr0, tlr1, tcsr0, tcsr1; > + u64 period_cycles, duty_cycles; > + unsigned long rate; > + > + if (state->polarity != PWM_POLARITY_NORMAL) > + return -EINVAL; > + > + /* > + * To be representable by TLR, cycles must be between 2 and > + * priv->max + 2. To enforce this we can reduce the cycles, but we may > + * not increase them. Caveat emptor: while this does result in more > + * predictable rounding, it may also result in a completely different > + * duty cycle (% high time) than what was requested. > + */ > + rate = clk_get_rate(priv->clk); > + /* Avoid overflow */ > + period_cycles = min_t(u64, state->period, ULONG_MAX * NSEC_PER_SEC); on a 64 bit platform ULONG_MAX * NSEC_PER_SEC doesn't fit into an u64 ... I think if you replace ULONG_MAX by U32_MAX it works as intended. > + period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC); > + period_cycles = min_t(u64, period_cycles, priv->max + 2); > + if (period_cycles < 2) > + return -ERANGE; > + > +[...] > +static void xilinx_pwm_get_state(struct pwm_chip *chip, > + struct pwm_device *unused, > + struct pwm_state *state) > +{ > + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); > + u32 tlr0, tlr1, tcsr0, tcsr1; > + > + regmap_read(priv->map, TLR0, &tlr0); > + regmap_read(priv->map, TLR1, &tlr1); > + regmap_read(priv->map, TCSR0, &tcsr0); > + regmap_read(priv->map, TCSR1, &tcsr1); > + state->period = xilinx_timer_get_period(priv, tlr0, tcsr0); > + state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1); > + state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1); > + state->polarity = PWM_POLARITY_NORMAL; > + > + /* 100% duty cycle results in constant low output */ > + if (state->period == state->duty_cycle) There is a corner case: It can happen that xilinx_timer_get_period(priv, tlr0, tcsr0) == xilinx_timer_get_period(priv, tlr1, tcsr1) but not tlr0 == tlr1. This only happens for clkrate > 1000000000, but given that the fix is cheap (i.e. check tlr0 == tlr1 instead of state->period == state->duty_cycle) I'd suggest to do that. > + state->duty_cycle = 0; > +} Best regards Uwe
On 1/31/22 11:40 AM, Sean Anderson wrote: > > > On 1/31/22 9:10 AM, Uwe Kleine-König wrote: >> Hello, >> >> first of all: Sorry for taking so long for the next review round. >> >>> diff --git a/arch/microblaze/kernel/timer.c b/arch/microblaze/kernel/timer.c >>> index f8832cf49384..26c385582c3b 100644 >>> --- a/arch/microblaze/kernel/timer.c >>> +++ b/arch/microblaze/kernel/timer.c >>> @@ -251,6 +251,10 @@ static int __init xilinx_timer_init(struct device_node *timer) >>> u32 timer_num = 1; >>> int ret; >>> >>> + /* If this property is present, the device is a PWM and not a timer */ >>> + if (of_property_read_bool(timer, "#pwm-cells")) >>> + return 0; >>> + >>> if (initialized) >>> return -EINVAL; >>> >>> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig >>> index 21e3b05a5153..cefbf00b4c7e 100644 >>> --- a/drivers/pwm/Kconfig >>> +++ b/drivers/pwm/Kconfig >>> @@ -640,4 +640,18 @@ config PWM_VT8500 >>> To compile this driver as a module, choose M here: the module >>> will be called pwm-vt8500. >>> >>> +config PWM_XILINX >>> + tristate "Xilinx AXI Timer PWM support" >>> + depends on OF_ADDRESS >>> + depends on COMMON_CLK >>> + select REGMAP_MMIO >>> + help >>> + PWM driver for Xilinx LogiCORE IP AXI timers. This timer is >>> + typically a soft core which may be present in Xilinx FPGAs. >>> + This device may also be present in Microblaze soft processors. >>> + If you don't have this IP in your design, choose N. >>> + >>> + To compile this driver as a module, choose M here: the module >>> + will be called pwm-xilinx. >>> + >>> endif >>> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile >>> index 708840b7fba8..ea785480359b 100644 >>> --- a/drivers/pwm/Makefile >>> +++ b/drivers/pwm/Makefile >>> @@ -60,3 +60,4 @@ obj-$(CONFIG_PWM_TWL) += pwm-twl.o >>> obj-$(CONFIG_PWM_TWL_LED) += pwm-twl-led.o >>> obj-$(CONFIG_PWM_VISCONTI) += pwm-visconti.o >>> obj-$(CONFIG_PWM_VT8500) += pwm-vt8500.o >>> +obj-$(CONFIG_PWM_XILINX) += pwm-xilinx.o >>> diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c >>> new file mode 100644 >>> index 000000000000..b4d93e8812c6 >>> --- /dev/null >>> +++ b/drivers/pwm/pwm-xilinx.c >>> @@ -0,0 +1,319 @@ >>> +// SPDX-License-Identifier: GPL-2.0+ >>> +/* >>> + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> >>> + * >>> + * Limitations: >>> + * - When changing both duty cycle and period, we may end up with one cycle >>> + * with the old duty cycle and the new period. This is because the counters >>> + * may only be reloaded by first stopping them, or by letting them be >>> + * automatically reloaded at the end of a cycle. If this automatic reload >>> + * happens after we set TLR0 but before we set TLR1 then we will have a >>> + * bad cycle. This could probably be fixed by reading TCR0 just before >>> + * reprogramming, but I think it would add complexity for little gain. >>> + * - Cannot produce 100% duty cycle by configuring the TLRs. This might be >>> + * possible by stopping the counters at an appropriate point in the cycle, >>> + * but this is not (yet) implemented. >>> + * - Only produces "normal" output. >>> + * - Always produces low output if disabled. >>> + */ >>> + >>> +#include <clocksource/timer-xilinx.h> >>> +#include <linux/clk.h> >>> +#include <linux/clk-provider.h> >>> +#include <linux/device.h> >>> +#include <linux/module.h> >>> +#include <linux/of.h> >>> +#include <linux/platform_device.h> >>> +#include <linux/pwm.h> >>> +#include <linux/regmap.h> >>> + >>> +/* >>> + * The following functions are "common" to drivers for this device, and may be >>> + * exported at a future date. >>> + */ >>> +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, >>> + u64 cycles) >>> +{ >>> + WARN_ON(cycles < 2 || cycles - 2 > priv->max); >>> + >>> + if (tcsr & TCSR_UDT) >>> + return cycles - 2; >>> + return priv->max - cycles + 2; >>> +} >>> + >>> +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, >>> + u32 tlr, u32 tcsr) >>> +{ >>> + u64 cycles; >>> + >>> + if (tcsr & TCSR_UDT) >>> + cycles = tlr + 2; >>> + else >>> + cycles = (u64)priv->max - tlr + 2; >>> + >>> + /* cycles has a max of 2^32 + 2 */ >> >> If you add "... so the multiplication doesn't overflow." it becomes more >> obvious why this comment is there. >> >>> + return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC, >>> + clk_get_rate(priv->clk)); >>> +} >>> + >>> +/* >>> + * The idea here is to capture whether the PWM is actually running (e.g. >>> + * because we or the bootloader set it up) and we need to be careful to ensure >>> + * we don't cause a glitch. According to the data sheet, to enable the PWM we >>> + * need to >>> + * >>> + * - Set both timers to generate mode (MDT=1) >>> + * - Set both timers to PWM mode (PWMA=1) >>> + * - Enable the generate out signals (GENT=1) >>> + * >>> + * In addition, >>> + * >>> + * - The timer must be running (ENT=1) >>> + * - The timer must auto-reload TLR into TCR (ARHT=1) >>> + * - We must not be in the process of loading TLR into TCR (LOAD=0) >>> + * - Cascade mode must be disabled (CASC=0) >>> + * >>> + * If any of these differ from usual, then the PWM is either disabled, or is >>> + * running in a mode that this driver does not support. >>> + */ >>> +#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA) >>> +#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD) >>> +#define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR) >>> + >>> +struct xilinx_pwm_device { >>> + struct pwm_chip chip; >>> + struct xilinx_timer_priv priv; >>> +}; >>> + >>> +static inline struct xilinx_timer_priv >>> +*xilinx_pwm_chip_to_priv(struct pwm_chip *chip) >>> +{ >>> + return &container_of(chip, struct xilinx_pwm_device, chip)->priv; >>> +} >>> + >>> +static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1) >>> +{ >>> + return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET && >>> + (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET; >>> +} >>> + >>> +static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused, >>> + const struct pwm_state *state) >>> +{ >>> + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); >>> + u32 tlr0, tlr1, tcsr0, tcsr1; >>> + u64 period_cycles, duty_cycles; >>> + unsigned long rate; >>> + >>> + if (state->polarity != PWM_POLARITY_NORMAL) >>> + return -EINVAL; >>> + >>> + /* >>> + * To be representable by TLR, cycles must be between 2 and >>> + * priv->max + 2. To enforce this we can reduce the cycles, but we may >>> + * not increase them. Caveat emptor: while this does result in more >>> + * predictable rounding, it may also result in a completely different >>> + * duty cycle (% high time) than what was requested. >>> + */ >>> + rate = clk_get_rate(priv->clk); >>> + /* Avoid overflow */ >>> + period_cycles = min_t(u64, state->period, ULONG_MAX * NSEC_PER_SEC); >> >> on a 64 bit platform ULONG_MAX * NSEC_PER_SEC doesn't fit into an u64 >> ... I think if you replace ULONG_MAX by U32_MAX it works as intended. >> >>> + period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC); >>> + period_cycles = min_t(u64, period_cycles, priv->max + 2); >>> + if (period_cycles < 2) >>> + return -ERANGE; >>> + >>> +[...] >>> +static void xilinx_pwm_get_state(struct pwm_chip *chip, >>> + struct pwm_device *unused, >>> + struct pwm_state *state) >>> +{ >>> + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); >>> + u32 tlr0, tlr1, tcsr0, tcsr1; >>> + >>> + regmap_read(priv->map, TLR0, &tlr0); >>> + regmap_read(priv->map, TLR1, &tlr1); >>> + regmap_read(priv->map, TCSR0, &tcsr0); >>> + regmap_read(priv->map, TCSR1, &tcsr1); >>> + state->period = xilinx_timer_get_period(priv, tlr0, tcsr0); >>> + state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1); >>> + state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1); >>> + state->polarity = PWM_POLARITY_NORMAL; >>> + >>> + /* 100% duty cycle results in constant low output */ >>> + if (state->period == state->duty_cycle) >> >> There is a corner case: It can happen that >> xilinx_timer_get_period(priv, tlr0, tcsr0) == >> xilinx_timer_get_period(priv, tlr1, tcsr1) but not tlr0 == tlr1. >> >> This only happens for clkrate > 1000000000, but given that the fix is >> cheap (i.e. check tlr0 == tlr1 instead of state->period == >> state->duty_cycle) I'd suggest to do that. > This is intentional. xilinx_timer_get_period abstracts over whether UDT is set or not. I will fix this when you find me this hardware implemented with a 1GHz clock. --Sean
On Fri, Feb 04, 2022 at 12:51:28PM -0500, Sean Anderson wrote: > > > On 1/31/22 11:40 AM, Sean Anderson wrote: > > > > > > On 1/31/22 9:10 AM, Uwe Kleine-König wrote: > >> Hello, > >> > >> first of all: Sorry for taking so long for the next review round. > >> > >>> diff --git a/arch/microblaze/kernel/timer.c b/arch/microblaze/kernel/timer.c > >>> index f8832cf49384..26c385582c3b 100644 > >>> --- a/arch/microblaze/kernel/timer.c > >>> +++ b/arch/microblaze/kernel/timer.c > >>> @@ -251,6 +251,10 @@ static int __init xilinx_timer_init(struct device_node *timer) > >>> u32 timer_num = 1; > >>> int ret; > >>> > >>> + /* If this property is present, the device is a PWM and not a timer */ > >>> + if (of_property_read_bool(timer, "#pwm-cells")) > >>> + return 0; > >>> + > >>> if (initialized) > >>> return -EINVAL; > >>> > >>> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > >>> index 21e3b05a5153..cefbf00b4c7e 100644 > >>> --- a/drivers/pwm/Kconfig > >>> +++ b/drivers/pwm/Kconfig > >>> @@ -640,4 +640,18 @@ config PWM_VT8500 > >>> To compile this driver as a module, choose M here: the module > >>> will be called pwm-vt8500. > >>> > >>> +config PWM_XILINX > >>> + tristate "Xilinx AXI Timer PWM support" > >>> + depends on OF_ADDRESS > >>> + depends on COMMON_CLK > >>> + select REGMAP_MMIO > >>> + help > >>> + PWM driver for Xilinx LogiCORE IP AXI timers. This timer is > >>> + typically a soft core which may be present in Xilinx FPGAs. > >>> + This device may also be present in Microblaze soft processors. > >>> + If you don't have this IP in your design, choose N. > >>> + > >>> + To compile this driver as a module, choose M here: the module > >>> + will be called pwm-xilinx. > >>> + > >>> endif > >>> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > >>> index 708840b7fba8..ea785480359b 100644 > >>> --- a/drivers/pwm/Makefile > >>> +++ b/drivers/pwm/Makefile > >>> @@ -60,3 +60,4 @@ obj-$(CONFIG_PWM_TWL) += pwm-twl.o > >>> obj-$(CONFIG_PWM_TWL_LED) += pwm-twl-led.o > >>> obj-$(CONFIG_PWM_VISCONTI) += pwm-visconti.o > >>> obj-$(CONFIG_PWM_VT8500) += pwm-vt8500.o > >>> +obj-$(CONFIG_PWM_XILINX) += pwm-xilinx.o > >>> diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c > >>> new file mode 100644 > >>> index 000000000000..b4d93e8812c6 > >>> --- /dev/null > >>> +++ b/drivers/pwm/pwm-xilinx.c > >>> @@ -0,0 +1,319 @@ > >>> +// SPDX-License-Identifier: GPL-2.0+ > >>> +/* > >>> + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> > >>> + * > >>> + * Limitations: > >>> + * - When changing both duty cycle and period, we may end up with one cycle > >>> + * with the old duty cycle and the new period. This is because the counters > >>> + * may only be reloaded by first stopping them, or by letting them be > >>> + * automatically reloaded at the end of a cycle. If this automatic reload > >>> + * happens after we set TLR0 but before we set TLR1 then we will have a > >>> + * bad cycle. This could probably be fixed by reading TCR0 just before > >>> + * reprogramming, but I think it would add complexity for little gain. > >>> + * - Cannot produce 100% duty cycle by configuring the TLRs. This might be > >>> + * possible by stopping the counters at an appropriate point in the cycle, > >>> + * but this is not (yet) implemented. > >>> + * - Only produces "normal" output. > >>> + * - Always produces low output if disabled. > >>> + */ > >>> + > >>> +#include <clocksource/timer-xilinx.h> > >>> +#include <linux/clk.h> > >>> +#include <linux/clk-provider.h> > >>> +#include <linux/device.h> > >>> +#include <linux/module.h> > >>> +#include <linux/of.h> > >>> +#include <linux/platform_device.h> > >>> +#include <linux/pwm.h> > >>> +#include <linux/regmap.h> > >>> + > >>> +/* > >>> + * The following functions are "common" to drivers for this device, and may be > >>> + * exported at a future date. > >>> + */ > >>> +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, > >>> + u64 cycles) > >>> +{ > >>> + WARN_ON(cycles < 2 || cycles - 2 > priv->max); > >>> + > >>> + if (tcsr & TCSR_UDT) > >>> + return cycles - 2; > >>> + return priv->max - cycles + 2; > >>> +} > >>> + > >>> +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, > >>> + u32 tlr, u32 tcsr) > >>> +{ > >>> + u64 cycles; > >>> + > >>> + if (tcsr & TCSR_UDT) > >>> + cycles = tlr + 2; > >>> + else > >>> + cycles = (u64)priv->max - tlr + 2; > >>> + > >>> + /* cycles has a max of 2^32 + 2 */ > >> > >> If you add "... so the multiplication doesn't overflow." it becomes more > >> obvious why this comment is there. > >> > >>> + return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC, > >>> + clk_get_rate(priv->clk)); > >>> +} > >>> + > >>> +/* > >>> + * The idea here is to capture whether the PWM is actually running (e.g. > >>> + * because we or the bootloader set it up) and we need to be careful to ensure > >>> + * we don't cause a glitch. According to the data sheet, to enable the PWM we > >>> + * need to > >>> + * > >>> + * - Set both timers to generate mode (MDT=1) > >>> + * - Set both timers to PWM mode (PWMA=1) > >>> + * - Enable the generate out signals (GENT=1) > >>> + * > >>> + * In addition, > >>> + * > >>> + * - The timer must be running (ENT=1) > >>> + * - The timer must auto-reload TLR into TCR (ARHT=1) > >>> + * - We must not be in the process of loading TLR into TCR (LOAD=0) > >>> + * - Cascade mode must be disabled (CASC=0) > >>> + * > >>> + * If any of these differ from usual, then the PWM is either disabled, or is > >>> + * running in a mode that this driver does not support. > >>> + */ > >>> +#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA) > >>> +#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD) > >>> +#define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR) > >>> + > >>> +struct xilinx_pwm_device { > >>> + struct pwm_chip chip; > >>> + struct xilinx_timer_priv priv; > >>> +}; > >>> + > >>> +static inline struct xilinx_timer_priv > >>> +*xilinx_pwm_chip_to_priv(struct pwm_chip *chip) > >>> +{ > >>> + return &container_of(chip, struct xilinx_pwm_device, chip)->priv; > >>> +} > >>> + > >>> +static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1) > >>> +{ > >>> + return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET && > >>> + (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET; > >>> +} > >>> + > >>> +static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused, > >>> + const struct pwm_state *state) > >>> +{ > >>> + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); > >>> + u32 tlr0, tlr1, tcsr0, tcsr1; > >>> + u64 period_cycles, duty_cycles; > >>> + unsigned long rate; > >>> + > >>> + if (state->polarity != PWM_POLARITY_NORMAL) > >>> + return -EINVAL; > >>> + > >>> + /* > >>> + * To be representable by TLR, cycles must be between 2 and > >>> + * priv->max + 2. To enforce this we can reduce the cycles, but we may > >>> + * not increase them. Caveat emptor: while this does result in more > >>> + * predictable rounding, it may also result in a completely different > >>> + * duty cycle (% high time) than what was requested. > >>> + */ > >>> + rate = clk_get_rate(priv->clk); > >>> + /* Avoid overflow */ > >>> + period_cycles = min_t(u64, state->period, ULONG_MAX * NSEC_PER_SEC); > >> > >> on a 64 bit platform ULONG_MAX * NSEC_PER_SEC doesn't fit into an u64 > >> ... I think if you replace ULONG_MAX by U32_MAX it works as intended. > >> > >>> + period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC); > >>> + period_cycles = min_t(u64, period_cycles, priv->max + 2); > >>> + if (period_cycles < 2) > >>> + return -ERANGE; > >>> + > >>> +[...] > >>> +static void xilinx_pwm_get_state(struct pwm_chip *chip, > >>> + struct pwm_device *unused, > >>> + struct pwm_state *state) > >>> +{ > >>> + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); > >>> + u32 tlr0, tlr1, tcsr0, tcsr1; > >>> + > >>> + regmap_read(priv->map, TLR0, &tlr0); > >>> + regmap_read(priv->map, TLR1, &tlr1); > >>> + regmap_read(priv->map, TCSR0, &tcsr0); > >>> + regmap_read(priv->map, TCSR1, &tcsr1); > >>> + state->period = xilinx_timer_get_period(priv, tlr0, tcsr0); > >>> + state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1); > >>> + state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1); > >>> + state->polarity = PWM_POLARITY_NORMAL; > >>> + > >>> + /* 100% duty cycle results in constant low output */ > >>> + if (state->period == state->duty_cycle) > >> > >> There is a corner case: It can happen that > >> xilinx_timer_get_period(priv, tlr0, tcsr0) == > >> xilinx_timer_get_period(priv, tlr1, tcsr1) but not tlr0 == tlr1. > >> > >> This only happens for clkrate > 1000000000, but given that the fix is > >> cheap (i.e. check tlr0 == tlr1 instead of state->period == > >> state->duty_cycle) I'd suggest to do that. > > This is intentional. xilinx_timer_get_period abstracts over whether UDT > is set or not. I will fix this when you find me this hardware > implemented with a 1GHz clock. So it can happen, that UDT is set for tlr0 but not for tlr1? For a future you: Can I convince you to add a check for the maximal clk freq such that finding that issue again when 1 GHz becomes normal is easier? Having said that, I wonder what happens if the TLR1 > TLR0? Best regards Uwe
diff --git a/MAINTAINERS b/MAINTAINERS index 13f9a84a617e..373757fcc8c6 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -20925,6 +20925,12 @@ F: drivers/misc/Makefile F: drivers/misc/xilinx_sdfec.c F: include/uapi/misc/xilinx_sdfec.h +XILINX PWM DRIVER +M: Sean Anderson <sean.anderson@seco.com> +S: Maintained +F: drivers/pwm/pwm-xilinx.c +F: include/clocksource/timer-xilinx.h + XILINX UARTLITE SERIAL DRIVER M: Peter Korsgaard <jacmet@sunsite.dk> L: linux-serial@vger.kernel.org diff --git a/arch/microblaze/kernel/timer.c b/arch/microblaze/kernel/timer.c index f8832cf49384..26c385582c3b 100644 --- a/arch/microblaze/kernel/timer.c +++ b/arch/microblaze/kernel/timer.c @@ -251,6 +251,10 @@ static int __init xilinx_timer_init(struct device_node *timer) u32 timer_num = 1; int ret; + /* If this property is present, the device is a PWM and not a timer */ + if (of_property_read_bool(timer, "#pwm-cells")) + return 0; + if (initialized) return -EINVAL; diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 21e3b05a5153..cefbf00b4c7e 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -640,4 +640,18 @@ config PWM_VT8500 To compile this driver as a module, choose M here: the module will be called pwm-vt8500. +config PWM_XILINX + tristate "Xilinx AXI Timer PWM support" + depends on OF_ADDRESS + depends on COMMON_CLK + select REGMAP_MMIO + help + PWM driver for Xilinx LogiCORE IP AXI timers. This timer is + typically a soft core which may be present in Xilinx FPGAs. + This device may also be present in Microblaze soft processors. + If you don't have this IP in your design, choose N. + + To compile this driver as a module, choose M here: the module + will be called pwm-xilinx. + endif diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index 708840b7fba8..ea785480359b 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -60,3 +60,4 @@ obj-$(CONFIG_PWM_TWL) += pwm-twl.o obj-$(CONFIG_PWM_TWL_LED) += pwm-twl-led.o obj-$(CONFIG_PWM_VISCONTI) += pwm-visconti.o obj-$(CONFIG_PWM_VT8500) += pwm-vt8500.o +obj-$(CONFIG_PWM_XILINX) += pwm-xilinx.o diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c new file mode 100644 index 000000000000..b4d93e8812c6 --- /dev/null +++ b/drivers/pwm/pwm-xilinx.c @@ -0,0 +1,319 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> + * + * Limitations: + * - When changing both duty cycle and period, we may end up with one cycle + * with the old duty cycle and the new period. This is because the counters + * may only be reloaded by first stopping them, or by letting them be + * automatically reloaded at the end of a cycle. If this automatic reload + * happens after we set TLR0 but before we set TLR1 then we will have a + * bad cycle. This could probably be fixed by reading TCR0 just before + * reprogramming, but I think it would add complexity for little gain. + * - Cannot produce 100% duty cycle by configuring the TLRs. This might be + * possible by stopping the counters at an appropriate point in the cycle, + * but this is not (yet) implemented. + * - Only produces "normal" output. + * - Always produces low output if disabled. + */ + +#include <clocksource/timer-xilinx.h> +#include <linux/clk.h> +#include <linux/clk-provider.h> +#include <linux/device.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> +#include <linux/regmap.h> + +/* + * The following functions are "common" to drivers for this device, and may be + * exported at a future date. + */ +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, + u64 cycles) +{ + WARN_ON(cycles < 2 || cycles - 2 > priv->max); + + if (tcsr & TCSR_UDT) + return cycles - 2; + return priv->max - cycles + 2; +} + +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, + u32 tlr, u32 tcsr) +{ + u64 cycles; + + if (tcsr & TCSR_UDT) + cycles = tlr + 2; + else + cycles = (u64)priv->max - tlr + 2; + + /* cycles has a max of 2^32 + 2 */ + return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC, + clk_get_rate(priv->clk)); +} + +/* + * The idea here is to capture whether the PWM is actually running (e.g. + * because we or the bootloader set it up) and we need to be careful to ensure + * we don't cause a glitch. According to the data sheet, to enable the PWM we + * need to + * + * - Set both timers to generate mode (MDT=1) + * - Set both timers to PWM mode (PWMA=1) + * - Enable the generate out signals (GENT=1) + * + * In addition, + * + * - The timer must be running (ENT=1) + * - The timer must auto-reload TLR into TCR (ARHT=1) + * - We must not be in the process of loading TLR into TCR (LOAD=0) + * - Cascade mode must be disabled (CASC=0) + * + * If any of these differ from usual, then the PWM is either disabled, or is + * running in a mode that this driver does not support. + */ +#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA) +#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD) +#define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR) + +struct xilinx_pwm_device { + struct pwm_chip chip; + struct xilinx_timer_priv priv; +}; + +static inline struct xilinx_timer_priv +*xilinx_pwm_chip_to_priv(struct pwm_chip *chip) +{ + return &container_of(chip, struct xilinx_pwm_device, chip)->priv; +} + +static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1) +{ + return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET && + (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET; +} + +static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused, + const struct pwm_state *state) +{ + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); + u32 tlr0, tlr1, tcsr0, tcsr1; + u64 period_cycles, duty_cycles; + unsigned long rate; + + if (state->polarity != PWM_POLARITY_NORMAL) + return -EINVAL; + + /* + * To be representable by TLR, cycles must be between 2 and + * priv->max + 2. To enforce this we can reduce the cycles, but we may + * not increase them. Caveat emptor: while this does result in more + * predictable rounding, it may also result in a completely different + * duty cycle (% high time) than what was requested. + */ + rate = clk_get_rate(priv->clk); + /* Avoid overflow */ + period_cycles = min_t(u64, state->period, ULONG_MAX * NSEC_PER_SEC); + period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC); + period_cycles = min_t(u64, period_cycles, priv->max + 2); + if (period_cycles < 2) + return -ERANGE; + + /* Same thing for duty cycles */ + duty_cycles = min_t(u64, state->duty_cycle, ULONG_MAX * NSEC_PER_SEC); + duty_cycles = mul_u64_u32_div(duty_cycles, rate, NSEC_PER_SEC); + duty_cycles = min_t(u64, duty_cycles, priv->max + 2); + + /* + * If we specify 100% duty cycle, we will get 0% instead, so decrease + * the duty cycle count by one. + */ + if (duty_cycles >= period_cycles) + duty_cycles = period_cycles - 1; + + /* Round down to 0% duty cycle for unrepresentable duty cycles */ + if (duty_cycles < 2) + duty_cycles = period_cycles; + + regmap_read(priv->map, TCSR0, &tcsr0); + regmap_read(priv->map, TCSR1, &tcsr1); + tlr0 = xilinx_timer_tlr_cycles(priv, tcsr0, period_cycles); + tlr1 = xilinx_timer_tlr_cycles(priv, tcsr1, duty_cycles); + regmap_write(priv->map, TLR0, tlr0); + regmap_write(priv->map, TLR1, tlr1); + + if (state->enabled) { + /* + * If the PWM is already running, then the counters will be + * reloaded at the end of the current cycle. + */ + if (!xilinx_timer_pwm_enabled(tcsr0, tcsr1)) { + /* Load TLR into TCR */ + regmap_write(priv->map, TCSR0, tcsr0 | TCSR_LOAD); + regmap_write(priv->map, TCSR1, tcsr1 | TCSR_LOAD); + /* Enable timers all at once with ENALL */ + tcsr0 = (TCSR_PWM_SET & ~TCSR_ENT) | (tcsr0 & TCSR_UDT); + tcsr1 = TCSR_PWM_SET | TCSR_ENALL | (tcsr1 & TCSR_UDT); + regmap_write(priv->map, TCSR0, tcsr0); + regmap_write(priv->map, TCSR1, tcsr1); + } + } else { + regmap_write(priv->map, TCSR0, 0); + regmap_write(priv->map, TCSR1, 0); + } + + return 0; +} + +static void xilinx_pwm_get_state(struct pwm_chip *chip, + struct pwm_device *unused, + struct pwm_state *state) +{ + struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip); + u32 tlr0, tlr1, tcsr0, tcsr1; + + regmap_read(priv->map, TLR0, &tlr0); + regmap_read(priv->map, TLR1, &tlr1); + regmap_read(priv->map, TCSR0, &tcsr0); + regmap_read(priv->map, TCSR1, &tcsr1); + state->period = xilinx_timer_get_period(priv, tlr0, tcsr0); + state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1); + state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1); + state->polarity = PWM_POLARITY_NORMAL; + + /* 100% duty cycle results in constant low output */ + if (state->period == state->duty_cycle) + state->duty_cycle = 0; +} + +static const struct pwm_ops xilinx_pwm_ops = { + .apply = xilinx_pwm_apply, + .get_state = xilinx_pwm_get_state, + .owner = THIS_MODULE, +}; + +static const struct regmap_config xilinx_pwm_regmap_config = { + .reg_bits = 32, + .reg_stride = 4, + .val_bits = 32, + .val_format_endian = REGMAP_ENDIAN_LITTLE, + .max_register = TCR1, +}; + +static int xilinx_pwm_probe(struct platform_device *pdev) +{ + int ret; + struct device *dev = &pdev->dev; + struct device_node *np = dev->of_node; + struct xilinx_timer_priv *priv; + struct xilinx_pwm_device *xilinx_pwm; + u32 pwm_cells, one_timer, width; + void __iomem *regs; + + /* If there are no PWM cells, this binding is for a timer */ + ret = of_property_read_u32(np, "#pwm-cells", &pwm_cells); + if (ret == -EINVAL) + return -ENODEV; + if (ret) + return dev_err_probe(dev, ret, "could not read #pwm-cells\n"); + + xilinx_pwm = devm_kzalloc(dev, sizeof(*xilinx_pwm), GFP_KERNEL); + if (!xilinx_pwm) + return -ENOMEM; + platform_set_drvdata(pdev, xilinx_pwm); + priv = &xilinx_pwm->priv; + + regs = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(regs)) + return PTR_ERR(regs); + + priv->map = devm_regmap_init_mmio(dev, regs, + &xilinx_pwm_regmap_config); + if (IS_ERR(priv->map)) + return dev_err_probe(dev, PTR_ERR(priv->map), + "Could not create regmap\n"); + + ret = of_property_read_u32(np, "xlnx,one-timer-only", &one_timer); + if (ret) + return dev_err_probe(dev, ret, + "Could not read xlnx,one-timer-only\n"); + + if (one_timer) + return dev_err_probe(dev, -EINVAL, + "Two timers required for PWM mode\n"); + + + ret = of_property_read_u32(np, "xlnx,count-width", &width); + if (ret == -EINVAL) + width = 32; + else if (ret) + return dev_err_probe(dev, ret, + "Could not read xlnx,count-width\n"); + + if (width != 8 && width != 16 && width != 32) + return dev_err_probe(dev, -EINVAL, + "Invalid counter width %d\n", width); + priv->max = BIT_ULL(width) - 1; + + /* + * The polarity of the Generate Out signals must be active high for PWM + * mode to work. We could determine this from the device tree, but + * alas, such properties are not allowed to be used. + */ + + priv->clk = devm_clk_get(dev, "s_axi_aclk"); + if (IS_ERR(priv->clk)) + return dev_err_probe(dev, PTR_ERR(priv->clk), + "Could not get clock\n"); + + ret = clk_prepare_enable(priv->clk); + if (ret) + return dev_err_probe(dev, ret, "Clock enable failed\n"); + clk_rate_exclusive_get(priv->clk); + + xilinx_pwm->chip.dev = dev; + xilinx_pwm->chip.ops = &xilinx_pwm_ops; + xilinx_pwm->chip.npwm = 1; + ret = pwmchip_add(&xilinx_pwm->chip); + if (ret) { + clk_rate_exclusive_put(priv->clk); + clk_disable_unprepare(priv->clk); + return dev_err_probe(dev, ret, "Could not register PWM chip\n"); + } + + return 0; +} + +static int xilinx_pwm_remove(struct platform_device *pdev) +{ + struct xilinx_pwm_device *xilinx_pwm = platform_get_drvdata(pdev); + + pwmchip_remove(&xilinx_pwm->chip); + clk_rate_exclusive_put(xilinx_pwm->priv.clk); + clk_disable_unprepare(xilinx_pwm->priv.clk); + return 0; +} + +static const struct of_device_id xilinx_pwm_of_match[] = { + { .compatible = "xlnx,xps-timer-1.00.a", }, + {}, +}; +MODULE_DEVICE_TABLE(of, xilinx_pwm_of_match); + +static struct platform_driver xilinx_pwm_driver = { + .probe = xilinx_pwm_probe, + .remove = xilinx_pwm_remove, + .driver = { + .name = "xilinx-pwm", + .of_match_table = of_match_ptr(xilinx_pwm_of_match), + }, +}; +module_platform_driver(xilinx_pwm_driver); + +MODULE_ALIAS("platform:xilinx-pwm"); +MODULE_DESCRIPTION("PWM driver for Xilinx LogiCORE IP AXI Timer"); +MODULE_LICENSE("GPL v2"); diff --git a/include/clocksource/timer-xilinx.h b/include/clocksource/timer-xilinx.h new file mode 100644 index 000000000000..1f7757b84a5e --- /dev/null +++ b/include/clocksource/timer-xilinx.h @@ -0,0 +1,91 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com> + */ + +#ifndef XILINX_TIMER_H +#define XILINX_TIMER_H + +#include <linux/compiler.h> + +#define TCSR0 0x00 +#define TLR0 0x04 +#define TCR0 0x08 +#define TCSR1 0x10 +#define TLR1 0x14 +#define TCR1 0x18 + +#define TCSR_MDT BIT(0) +#define TCSR_UDT BIT(1) +#define TCSR_GENT BIT(2) +#define TCSR_CAPT BIT(3) +#define TCSR_ARHT BIT(4) +#define TCSR_LOAD BIT(5) +#define TCSR_ENIT BIT(6) +#define TCSR_ENT BIT(7) +#define TCSR_TINT BIT(8) +#define TCSR_PWMA BIT(9) +#define TCSR_ENALL BIT(10) +#define TCSR_CASC BIT(11) + +struct clk; +struct device_node; +struct regmap; + +/** + * struct xilinx_timer_priv - Private data for Xilinx AXI timer drivers + * @map: Regmap of the device, possibly with an offset + * @clk: Parent clock + * @max: Maximum value of the counters + */ +struct xilinx_timer_priv { + struct regmap *map; + struct clk *clk; + u32 max; +}; + +/** + * xilinx_timer_tlr_cycles() - Calculate the TLR for a period specified + * in clock cycles + * @priv: The timer's private data + * @tcsr: The value of the TCSR register for this counter + * @cycles: The number of cycles in this period + * + * Callers of this function MUST ensure that @cycles is representable as + * a TLR. + * + * Return: The calculated value for TLR + */ +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, + u64 cycles); + +/** + * xilinx_timer_get_period() - Get the current period of a counter + * @priv: The timer's private data + * @tlr: The value of TLR for this counter + * @tcsr: The value of TCSR for this counter + * + * Return: The period, in ns + */ +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, + u32 tlr, u32 tcsr); + +/** + * xilinx_timer_common_init() - Perform common initialization for Xilinx + * AXI timer drivers. + * @priv: The timer's private data + * @np: The devicetree node for the timer + * @one_timer: Set to %1 if there is only one timer + * + * This performs common initialization, such as detecting endianness, + * and parsing devicetree properties. @priv->regs must be initialized + * before calling this function. This function initializes @priv->read, + * @priv->write, and @priv->width. + * + * Return: 0, or negative errno + */ +int xilinx_timer_common_init(struct device_node *np, + struct xilinx_timer_priv *priv, + u32 *one_timer); + +#endif /* XILINX_TIMER_H */