| Message ID | 20231128084236.157152-4-wenst@chromium.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | platform/chrome: Introduce DT hardware prober | expand |
On Tue, Nov 28, 2023 at 04:42:32PM +0800, Chen-Yu Tsai wrote: > Some devices are designed and manufactured with some components having > multiple drop-in replacement options. These components are often > connected to the mainboard via ribbon cables, having the same signals > and pin assignments across all options. These may include the display > panel and touchscreen on laptops and tablets, and the trackpad on > laptops. Sometimes which component option is used in a particular device > can be detected by some firmware provided identifier, other times that > information is not available, and the kernel has to try to probe each > device. > > This change attempts to make the "probe each device" case cleaner. The > current approach is to have all options added and enabled in the device > tree. The kernel would then bind each device and run each driver's probe > function. This works, but has been broken before due to the introduction > of asynchronous probing, causing multiple instances requesting "shared" > resources, such as pinmuxes, GPIO pins, interrupt lines, at the same > time, with only one instance succeeding. Work arounds for these include > moving the pinmux to the parent I2C controller, using GPIO hogs or > pinmux settings to keep the GPIO pins in some fixed configuration, and > requesting the interrupt line very late. Such configurations can be seen > on the MT8183 Krane Chromebook tablets, and the Qualcomm sc8280xp-based > Lenovo Thinkpad 13S. > > Instead of this delicate dance between drivers and device tree quirks, > this change introduces a simple I2C component prober. For any given > class of devices on the same I2C bus, it will go through all of them, > doing a simple I2C read transfer and see which one of them responds. > It will then enable the device that responds. > > This requires some minor modifications in the existing device tree. > The status for all the device nodes for the component options must be > set to "failed-needs-probe". This makes it clear that some mechanism is > needed to enable one of them, and also prevents the prober and device > drivers running at the same time. ... > +#include <linux/array_size.h> > +#include <linux/i2c.h> > +#include <linux/of.h> > +#include <linux/platform_device.h> init.h for init calls. > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > +{ > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) > + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) { > + int ret; Perhaps if (!of_machine_is_compatible(hw_prober_platforms[i].compatible)) continue; ? > + ret = hw_prober_platforms[i].prober(&pdev->dev, > + hw_prober_platforms[i].data); > + if (ret) > + return ret; > + } > + > + return 0; > +}
On Wed, Nov 29, 2023 at 12:26 AM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Tue, Nov 28, 2023 at 04:42:32PM +0800, Chen-Yu Tsai wrote: > > Some devices are designed and manufactured with some components having > > multiple drop-in replacement options. These components are often > > connected to the mainboard via ribbon cables, having the same signals > > and pin assignments across all options. These may include the display > > panel and touchscreen on laptops and tablets, and the trackpad on > > laptops. Sometimes which component option is used in a particular device > > can be detected by some firmware provided identifier, other times that > > information is not available, and the kernel has to try to probe each > > device. > > > > This change attempts to make the "probe each device" case cleaner. The > > current approach is to have all options added and enabled in the device > > tree. The kernel would then bind each device and run each driver's probe > > function. This works, but has been broken before due to the introduction > > of asynchronous probing, causing multiple instances requesting "shared" > > resources, such as pinmuxes, GPIO pins, interrupt lines, at the same > > time, with only one instance succeeding. Work arounds for these include > > moving the pinmux to the parent I2C controller, using GPIO hogs or > > pinmux settings to keep the GPIO pins in some fixed configuration, and > > requesting the interrupt line very late. Such configurations can be seen > > on the MT8183 Krane Chromebook tablets, and the Qualcomm sc8280xp-based > > Lenovo Thinkpad 13S. > > > > Instead of this delicate dance between drivers and device tree quirks, > > this change introduces a simple I2C component prober. For any given > > class of devices on the same I2C bus, it will go through all of them, > > doing a simple I2C read transfer and see which one of them responds. > > It will then enable the device that responds. > > > > This requires some minor modifications in the existing device tree. > > The status for all the device nodes for the component options must be > > set to "failed-needs-probe". This makes it clear that some mechanism is > > needed to enable one of them, and also prevents the prober and device > > drivers running at the same time. > > ... > > > +#include <linux/array_size.h> > > +#include <linux/i2c.h> > > +#include <linux/of.h> > > +#include <linux/platform_device.h> > > init.h for init calls. Added to next version. > > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > > +{ > > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) > > + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) { > > + int ret; > > Perhaps > > if (!of_machine_is_compatible(hw_prober_platforms[i].compatible)) > continue; > > ? Works for me. One less level of indentation. Thanks ChenYu > > + ret = hw_prober_platforms[i].prober(&pdev->dev, > > + hw_prober_platforms[i].data); > > + if (ret) > > + return ret; > > + } > > + > > + return 0; > > +} > > -- > With Best Regards, > Andy Shevchenko > >
Hi, On Tue, Nov 28, 2023 at 12:45 AM Chen-Yu Tsai <wenst@chromium.org> wrote: > > @@ -61,6 +61,17 @@ config CHROMEOS_TBMC > To compile this driver as a module, choose M here: the > module will be called chromeos_tbmc. > > +config CHROMEOS_OF_HW_PROBER > + bool "ChromeOS Device Tree Hardware Prober" Any reason that it can't be a module? > + depends on OF > + depends on I2C > + select OF_DYNAMIC > + default OF You probably don't want "default OF". This means that everyone will automatically get this new driver enabled which is unlikely to be right. > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > +{ > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) > + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) { > + int ret; > + > + ret = hw_prober_platforms[i].prober(&pdev->dev, > + hw_prober_platforms[i].data); > + if (ret) Should it only check for -EPROBE_DEFER here? ...and then maybe warn for other cases and go through the loop? If there's some error enabling the touchscreen I'd still want the trackpad to probe... > + return ret; > + } > + > + return 0; Random thought: once we get here, the driver is useless / just wasting memory. Any way to have it freed? ;-)
On Sat, Dec 2, 2023 at 8:58 AM Doug Anderson <dianders@chromium.org> wrote: > > Hi, > > On Tue, Nov 28, 2023 at 12:45 AM Chen-Yu Tsai <wenst@chromium.org> wrote: > > > > @@ -61,6 +61,17 @@ config CHROMEOS_TBMC > > To compile this driver as a module, choose M here: the > > module will be called chromeos_tbmc. > > > > +config CHROMEOS_OF_HW_PROBER > > + bool "ChromeOS Device Tree Hardware Prober" > > Any reason that it can't be a module? No technical one. However if it's a module, the user has to manually load it. So I think it's more of a usability thing. OOTH I think this needs to be a module if I2C is built as a module. Somehow I had thought of it at one point but then it slipped my mind. > > + depends on OF > > + depends on I2C > > + select OF_DYNAMIC > > + default OF > > You probably don't want "default OF". This means that everyone will > automatically get this new driver enabled which is unlikely to be > right. I thought this whole section was guarded behind KCONFIG_CHROME_PLATFORMS. So if the user has CHROME_PLATFORMS enabled and has OF enabled, they likely need the prober. > > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > > +{ > > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) > > + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) { > > + int ret; > > + > > + ret = hw_prober_platforms[i].prober(&pdev->dev, > > + hw_prober_platforms[i].data); > > + if (ret) > > Should it only check for -EPROBE_DEFER here? ...and then maybe warn > for other cases and go through the loop? If there's some error > enabling the touchscreen I'd still want the trackpad to probe... Makes sense. However there's no extra information to give in the warning though. > > + return ret; > > + } > > + > > + return 0; > > Random thought: once we get here, the driver is useless / just wasting > memory. Any way to have it freed? ;-) I don't think there is a good way to do that, except maybe marking all the functions as __init? But that likely doesn't work in combination with deferred probing (say the i2c driver is a module). ChenYu
On Mon, Dec 4, 2023 at 3:24 PM Chen-Yu Tsai <wenst@chromium.org> wrote: > > On Sat, Dec 2, 2023 at 8:58 AM Doug Anderson <dianders@chromium.org> wrote: > > > > Hi, > > > > On Tue, Nov 28, 2023 at 12:45 AM Chen-Yu Tsai <wenst@chromium.org> wrote: > > > > > > @@ -61,6 +61,17 @@ config CHROMEOS_TBMC > > > To compile this driver as a module, choose M here: the > > > module will be called chromeos_tbmc. > > > > > > +config CHROMEOS_OF_HW_PROBER > > > + bool "ChromeOS Device Tree Hardware Prober" > > > > Any reason that it can't be a module? > > No technical one. However if it's a module, the user has to manually load > it. So I think it's more of a usability thing. We could probably manually add module aliases. I thought about aliases against the machine compatibles, but there doesn't seem to be a device for it to trigger. Or target something common to ChromeOS devices like the EC? It's really hacky though. ChenYu > OOTH I think this needs to be a module if I2C is built as a module. > Somehow I had thought of it at one point but then it slipped my mind. > > > > + depends on OF > > > + depends on I2C > > > + select OF_DYNAMIC > > > + default OF > > > > You probably don't want "default OF". This means that everyone will > > automatically get this new driver enabled which is unlikely to be > > right. > > I thought this whole section was guarded behind KCONFIG_CHROME_PLATFORMS. > So if the user has CHROME_PLATFORMS enabled and has OF enabled, they > likely need the prober. > > > > +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) > > > +{ > > > + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) > > > + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) { > > > + int ret; > > > + > > > + ret = hw_prober_platforms[i].prober(&pdev->dev, > > > + hw_prober_platforms[i].data); > > > + if (ret) > > > > Should it only check for -EPROBE_DEFER here? ...and then maybe warn > > for other cases and go through the loop? If there's some error > > enabling the touchscreen I'd still want the trackpad to probe... > > Makes sense. However there's no extra information to give in the > warning though. > > > > + return ret; > > > + } > > > + > > > + return 0; > > > > Random thought: once we get here, the driver is useless / just wasting > > memory. Any way to have it freed? ;-) > > I don't think there is a good way to do that, except maybe marking all > the functions as __init? But that likely doesn't work in combination > with deferred probing (say the i2c driver is a module). > > ChenYu
diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig index 7a83346bfa53..aa161f2f09e3 100644 --- a/drivers/platform/chrome/Kconfig +++ b/drivers/platform/chrome/Kconfig @@ -61,6 +61,17 @@ config CHROMEOS_TBMC To compile this driver as a module, choose M here: the module will be called chromeos_tbmc. +config CHROMEOS_OF_HW_PROBER + bool "ChromeOS Device Tree Hardware Prober" + depends on OF + depends on I2C + select OF_DYNAMIC + default OF + help + This option enables the device tree hardware prober for ChromeOS + devices. The driver will probe the correct component variant in + devices that have multiple drop-in options for one component. + config CROS_EC tristate "ChromeOS Embedded Controller" select CROS_EC_PROTO diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile index 2dcc6ccc2302..21a9d5047053 100644 --- a/drivers/platform/chrome/Makefile +++ b/drivers/platform/chrome/Makefile @@ -8,6 +8,7 @@ obj-$(CONFIG_CHROMEOS_ACPI) += chromeos_acpi.o obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o obj-$(CONFIG_CHROMEOS_PRIVACY_SCREEN) += chromeos_privacy_screen.o obj-$(CONFIG_CHROMEOS_PSTORE) += chromeos_pstore.o +obj-$(CONFIG_CHROMEOS_OF_HW_PROBER) += chromeos_of_hw_prober.o obj-$(CONFIG_CHROMEOS_TBMC) += chromeos_tbmc.o obj-$(CONFIG_CROS_EC) += cros_ec.o obj-$(CONFIG_CROS_EC_I2C) += cros_ec_i2c.o diff --git a/drivers/platform/chrome/chromeos_of_hw_prober.c b/drivers/platform/chrome/chromeos_of_hw_prober.c new file mode 100644 index 000000000000..13aaad6382aa --- /dev/null +++ b/drivers/platform/chrome/chromeos_of_hw_prober.c @@ -0,0 +1,89 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * ChromeOS Device Tree Hardware Prober + * + * Copyright (c) 2023 Google LLC + */ + +#include <linux/array_size.h> +#include <linux/i2c.h> +#include <linux/of.h> +#include <linux/platform_device.h> + +#define DRV_NAME "chromeos_of_hw_prober" + +/** + * struct hw_prober_entry - Holds an entry for the hardware prober + * + * @compatible: compatible string to match against the machine + * @prober: prober function to call when machine matches + * @data: extra data for the prober function + */ +struct hw_prober_entry { + const char *compatible; + int (*prober)(struct device *dev, const void *data); + const void *data; +}; + +static int chromeos_i2c_component_prober(struct device *dev, const void *data) +{ + const char *type = data; + + return i2c_of_probe_component(dev, type); +} + +static const struct hw_prober_entry hw_prober_platforms[] = { + { .compatible = "google,hana", .prober = chromeos_i2c_component_prober, .data = "touchscreen" }, + { .compatible = "google,hana", .prober = chromeos_i2c_component_prober, .data = "trackpad" }, +}; + +static int chromeos_of_hw_prober_probe(struct platform_device *pdev) +{ + for (size_t i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) { + int ret; + + ret = hw_prober_platforms[i].prober(&pdev->dev, + hw_prober_platforms[i].data); + if (ret) + return ret; + } + + return 0; +} + +static struct platform_driver chromeos_of_hw_prober_driver = { + .probe = chromeos_of_hw_prober_probe, + .driver = { + .name = DRV_NAME, + }, +}; + +static int __init chromeos_of_hw_prober_driver_init(void) +{ + struct platform_device *pdev; + size_t i; + int ret; + + for (i = 0; i < ARRAY_SIZE(hw_prober_platforms); i++) + if (of_machine_is_compatible(hw_prober_platforms[i].compatible)) + break; + if (i == ARRAY_SIZE(hw_prober_platforms)) + return 0; + + ret = platform_driver_register(&chromeos_of_hw_prober_driver); + if (ret) + return ret; + + pdev = platform_device_register_simple(DRV_NAME, PLATFORM_DEVID_NONE, NULL, 0); + if (IS_ERR(pdev)) + goto err; + + return 0; + +err: + platform_driver_unregister(&chromeos_of_hw_prober_driver); + + return PTR_ERR(pdev); +} +device_initcall(chromeos_of_hw_prober_driver_init);
Some devices are designed and manufactured with some components having multiple drop-in replacement options. These components are often connected to the mainboard via ribbon cables, having the same signals and pin assignments across all options. These may include the display panel and touchscreen on laptops and tablets, and the trackpad on laptops. Sometimes which component option is used in a particular device can be detected by some firmware provided identifier, other times that information is not available, and the kernel has to try to probe each device. This change attempts to make the "probe each device" case cleaner. The current approach is to have all options added and enabled in the device tree. The kernel would then bind each device and run each driver's probe function. This works, but has been broken before due to the introduction of asynchronous probing, causing multiple instances requesting "shared" resources, such as pinmuxes, GPIO pins, interrupt lines, at the same time, with only one instance succeeding. Work arounds for these include moving the pinmux to the parent I2C controller, using GPIO hogs or pinmux settings to keep the GPIO pins in some fixed configuration, and requesting the interrupt line very late. Such configurations can be seen on the MT8183 Krane Chromebook tablets, and the Qualcomm sc8280xp-based Lenovo Thinkpad 13S. Instead of this delicate dance between drivers and device tree quirks, this change introduces a simple I2C component prober. For any given class of devices on the same I2C bus, it will go through all of them, doing a simple I2C read transfer and see which one of them responds. It will then enable the device that responds. This requires some minor modifications in the existing device tree. The status for all the device nodes for the component options must be set to "failed-needs-probe". This makes it clear that some mechanism is needed to enable one of them, and also prevents the prober and device drivers running at the same time. Signed-off-by: Chen-Yu Tsai <wenst@chromium.org> --- Changes since v2: - Addressed Rob's comments - Move remaining driver code to drivers/platform/chrome/ - Depend on rather than select CONFIG_I2C - Copy machine check to driver init function - Addressed Andy's comments - Explicitly mention "device tree" or OF in driver name, description and Kconfig symbol - Drop filename from inside the file - Switch to passing "struct device *" to shorten lines - Move "ret = 0" to just before for_each_child_of_node(i2c_node, node) - Make loop variable size_t (instead of unsigned int as Andy asked) - Use PLATFORM_DEVID_NONE instead of raw -1 - Use standard goto error path pattern in hw_prober_driver_init() - Changes since v1: - New patch --- drivers/platform/chrome/Kconfig | 11 +++ drivers/platform/chrome/Makefile | 1 + .../platform/chrome/chromeos_of_hw_prober.c | 89 +++++++++++++++++++ 3 files changed, 101 insertions(+) create mode 100644 drivers/platform/chrome/chromeos_of_hw_prober.c