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b=jzFWy995Y61nuOYwp9YyhrZOx2+zhdBFSCseZfeOF1rd+BKRQwPpsy6F087vIODzE ywhJYthsJ4ZbNilGNfQjPNpnMYYl9v46lJKXQlJRZjtkVBBwyskJI8/Em6wxX615AQ ySyC/73nS+Ahv0rY+3xxsyfWHhCYFwcDmya0tf/0= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from longitude ([37.201.214.162]) by mail.gmx.com (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MXXuB-1kguA51Akx-00Z2Ei; Tue, 01 Dec 2020 06:16:46 +0100 From: =?utf-8?q?Jonathan_Neusch=C3=A4fer?= To: linux-kernel@vger.kernel.org Subject: [PATCH v5 4/7] pwm: ntxec: Add driver for PWM function in Netronix EC Date: Tue, 1 Dec 2020 02:15:10 +0100 Message-Id: <20201201011513.1627028-5-j.neuschaefer@gmx.net> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201201011513.1627028-1-j.neuschaefer@gmx.net> References: <20201201011513.1627028-1-j.neuschaefer@gmx.net> MIME-Version: 1.0 X-Provags-ID: V03:K1:ca9Z38lTTxyARgHEHV/TktM9KWbcJaj4CY+vU2TiPpIJwGSunTb 55PpShIGhQFE0ZR0tNe5vZKaeJSdMBc04PI/nj/IAvHliRKtAw/6YyxHPGsGS/J+Gt8FSeu xGwCiX0VzpeuvquQm9bDK+dIJDdsDk1Uu34lP1oPCvwmUu+w4hTmG7zZ8vwNJyRSh+PMktb +VAXcSElqilddkKXoaDTg== X-UI-Out-Filterresults: notjunk:1;V03:K0:Qc0L3ZXK+CA=:BdRXXwDu8Gz9j8B/JfK7Xl PRT9PnCT+ybLIlKh9Bij3I/N2unthD7Wm8miRR1+KgjufX7ZNUpnezjJyglrisUccrd+4sfe+ vCxY2IMC3+t5BaUwSFgxp8wrC27RnoLbBdqZFg1T3e2C7XDk+KqFEmKO5A5VUzTJ55JvVcb6A /wwZWxtf2osIMiHhlPf3+DBihyIBdbrCvmEKFjeYpcsOcKvNB4Pztq37tH0QP1xzr2bKikXSg pGQrSx3vIA7iAKcgV6833mO37myN/wMgFseMWnlZwiO9G5/yXUEwUgM1w36MrxF0u6AFIK4zf OtXOoATyx0agzH8RjG+tux+gHeVP0e/aX4mfNviDis0lHA8QRTzSToggHzh3rGOjfVSZp9Y9s y0AKornW3xgGZqdTWdH/fRlDw0e8FyBjA4JzvIy6DRDKFFfdHx+KjS9RQ3mNDhO3zLIK7+6PM WcQGa46xRf8QkwBP+Fdl2z9pPNO/9pp+VXbPo+ZgFEsnhjtxky1zLfKFFgJMDrKXgWsTj3Dm3 G8mtXFSH32bXDfxyrel3qxVNXdmFQC3h/BmZI2jqy9j24yEyCI9u0Tzm0EYLxJNsGTNY/7lPX QdVRDMBXy7zDMXuKY5au1fqTzfousduQIcA7NwKDDq1ejqSIeeEidASn/dZOUnJV++tTrWHzk 3m8x9Kd0+QsKyYlb8nNKO8ryO9kcxssCiBl4ei5FWw+dHA9GEh1dTg6SfXef3BoCJcmrmGbY5 lFOqQuRToVW+yiVgYdP0tdTiHgQdFSLAdHC3SRTN+guUK2vQjNSErDoZLoElsC0YbIuMeFIrn EAE8B8lJmgSiIlOl1BitgjS9MWJjE4Gy8WBbaRwgzPGxvf+AziW2+XjHReuKIoXfsNazu0o6w qGNVa6hyPrYPvjfyzlng== X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201201_001724_893412_17C68CDC X-CRM114-Status: GOOD ( 34.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexandre Belloni , Heiko Stuebner , linux-pwm@vger.kernel.org, Linus Walleij , Thierry Reding , Fabio Estevam , linux-rtc@vger.kernel.org, Arnd Bergmann , Mauro Carvalho Chehab , Sam Ravnborg , Daniel Palmer , Andy Shevchenko , Andreas Kemnade , NXP Linux Team , =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , devicetree@vger.kernel.org, Stephan Gerhold , allen , Sascha Hauer , =?utf-8?q?Jonathan_Neusch=C3=A4fer?= , Lubomir Rintel , Rob Herring , Lee Jones , linux-arm-kernel@lists.infradead.org, Alessandro Zummo , Mark Brown , Pengutronix Kernel Team , Heiko Stuebner , Josua Mayer , Shawn Guo , "David S. Miller" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The Netronix EC provides a PWM output which is used for the backlight on some ebook readers. This patches adds a driver for the PWM output. The .get_state callback is not implemented, because the PWM state can't be read back from the hardware. Signed-off-by: Jonathan Neuschäfer --- v5: - Avoid truncation of period and duty cycle to 32 bits - Make ntxec_pwm_ops const - Use regmap_multi_reg_write - Add comment about get_state to ntxec_pwm_ops - Add comments about non-atomicity of (period, duty cycle) update v4: - https://lore.kernel.org/lkml/20201122222739.1455132-5-j.neuschaefer@gmx.net/ - Document hardware/driver limitations - Only accept normal polarity - Fix a typo ("zone" -> "zero") - change MAX_PERIOD_NS to 0xffff * 125 - Clamp period to the maximum rather than returning an error - Rename private struct pointer to priv - Rearrage control flow in _probe to save a few lines and a temporary variable - Add missing MODULE_ALIAS line - Spell out ODM v3: - https://lore.kernel.org/lkml/20200924192455.2484005-5-j.neuschaefer@gmx.net/ - Relicense as GPLv2 or later - Add email address to copyright line - Remove OF compatible string and don't include linux/of_device.h - Fix bogus ?: in return line - Don't use a comma after sentinels - Avoid ret |= ... pattern - Move 8-bit register conversion to ntxec.h v2: - https://lore.kernel.org/lkml/20200905133230.1014581-6-j.neuschaefer@gmx.net/ - Various grammar and style improvements, as suggested by Uwe Kleine-König, Lee Jones, and Alexandre Belloni - Switch to regmap - Prefix registers with NTXEC_REG_ - Add help text to the Kconfig option - Use the .apply callback instead of the old API - Add a #define for the time base (125ns) - Don't change device state in .probe; this avoids multiple problems - Rework division and overflow check logic to perform divisions in 32 bits - Avoid setting duty cycle to zero, to work around a hardware quirk --- drivers/pwm/Kconfig | 8 ++ drivers/pwm/Makefile | 1 + drivers/pwm/pwm-ntxec.c | 173 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 182 insertions(+) create mode 100644 drivers/pwm/pwm-ntxec.c -- 2.29.2 diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 63be5362fd3a5..815f329ed5b46 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -350,6 +350,14 @@ config PWM_MXS To compile this driver as a module, choose M here: the module will be called pwm-mxs. +config PWM_NTXEC + tristate "Netronix embedded controller PWM support" + depends on MFD_NTXEC + help + Say yes here if you want to support the PWM output of the embedded + controller found in certain e-book readers designed by the original + design manufacturer Netronix. + config PWM_OMAP_DMTIMER tristate "OMAP Dual-Mode Timer PWM support" depends on OF diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index cbdcd55d69eef..1deb29e6ae8e5 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -32,6 +32,7 @@ obj-$(CONFIG_PWM_MESON) += pwm-meson.o obj-$(CONFIG_PWM_MEDIATEK) += pwm-mediatek.o obj-$(CONFIG_PWM_MTK_DISP) += pwm-mtk-disp.o obj-$(CONFIG_PWM_MXS) += pwm-mxs.o +obj-$(CONFIG_PWM_NTXEC) += pwm-ntxec.o obj-$(CONFIG_PWM_OMAP_DMTIMER) += pwm-omap-dmtimer.o obj-$(CONFIG_PWM_PCA9685) += pwm-pca9685.o obj-$(CONFIG_PWM_PXA) += pwm-pxa.o diff --git a/drivers/pwm/pwm-ntxec.c b/drivers/pwm/pwm-ntxec.c new file mode 100644 index 0000000000000..d36c8f8c0a958 --- /dev/null +++ b/drivers/pwm/pwm-ntxec.c @@ -0,0 +1,173 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * The Netronix embedded controller is a microcontroller found in some + * e-book readers designed by the original design manufacturer Netronix, Inc. + * It contains RTC, battery monitoring, system power management, and PWM + * functionality. + * + * This driver implements PWM output. + * + * Copyright 2020 Jonathan Neuschäfer + * + * Limitations: + * - The get_state callback is not implemented, because the current state of + * the PWM output can't be read back from the hardware. + * - The hardware can only generate normal polarity output. + * - The period and duty cycle can't be changed together in one atomic action. + */ + +#include +#include +#include +#include +#include +#include + +struct ntxec_pwm { + struct device *dev; + struct ntxec *ec; + struct pwm_chip chip; +}; + +static struct ntxec_pwm *pwmchip_to_priv(struct pwm_chip *chip) +{ + return container_of(chip, struct ntxec_pwm, chip); +} + +#define NTXEC_REG_AUTO_OFF_HI 0xa1 +#define NTXEC_REG_AUTO_OFF_LO 0xa2 +#define NTXEC_REG_ENABLE 0xa3 +#define NTXEC_REG_PERIOD_LOW 0xa4 +#define NTXEC_REG_PERIOD_HIGH 0xa5 +#define NTXEC_REG_DUTY_LOW 0xa6 +#define NTXEC_REG_DUTY_HIGH 0xa7 + +/* + * The time base used in the EC is 8MHz, or 125ns. Period and duty cycle are + * measured in this unit. + */ +#define TIME_BASE_NS 125 + +/* + * The maximum input value (in nanoseconds) is determined by the time base and + * the range of the hardware registers that hold the converted value. + * It fits into 32 bits, so we can do our calculations in 32 bits as well. + */ +#define MAX_PERIOD_NS (TIME_BASE_NS * 0xffff) + +static int ntxec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm_dev, + const struct pwm_state *state) +{ + struct ntxec_pwm *priv = pwmchip_to_priv(pwm_dev->chip); + unsigned int period, duty; + struct reg_sequence regs[] = { + { NTXEC_REG_PERIOD_HIGH }, + { NTXEC_REG_PERIOD_LOW }, + { NTXEC_REG_DUTY_HIGH }, + { NTXEC_REG_DUTY_LOW } + }; + int res; + + if (state->polarity != PWM_POLARITY_NORMAL) + return -EINVAL; + + period = min_t(u64, state->period, MAX_PERIOD_NS); + duty = min_t(u64, state->duty_cycle, period); + + period /= TIME_BASE_NS; + duty /= TIME_BASE_NS; + + /* + * Changes to the period and duty cycle take effect as soon as the + * corresponding low byte is written, so the hardware may be configured + * to an inconsistent state after the period is written and before the + * duty cycle is fully written. If, in such a case, the old duty cycle + * is longer than the new period, the EC may output 100% for a moment. + */ + + regs[0].def = ntxec_reg8(period >> 8); + regs[1].def = ntxec_reg8(period); + regs[2].def = ntxec_reg8(duty >> 8); + regs[3].def = ntxec_reg8(duty); + + res = regmap_multi_reg_write(priv->ec->regmap, regs, ARRAY_SIZE(regs)); + if (res) + return res; + + /* + * Writing a duty cycle of zero puts the device into a state where + * writing a higher duty cycle doesn't result in the brightness that it + * usually results in. This can be fixed by cycling the ENABLE register. + * + * As a workaround, write ENABLE=0 when the duty cycle is zero. + */ + if (state->enabled && duty != 0) { + res = regmap_write(priv->ec->regmap, NTXEC_REG_ENABLE, ntxec_reg8(1)); + if (res) + return res; + + /* Disable the auto-off timer */ + res = regmap_write(priv->ec->regmap, NTXEC_REG_AUTO_OFF_HI, ntxec_reg8(0xff)); + if (res) + return res; + + return regmap_write(priv->ec->regmap, NTXEC_REG_AUTO_OFF_LO, ntxec_reg8(0xff)); + } else { + return regmap_write(priv->ec->regmap, NTXEC_REG_ENABLE, ntxec_reg8(0)); + } +} + +static const struct pwm_ops ntxec_pwm_ops = { + .owner = THIS_MODULE, + .apply = ntxec_pwm_apply, + /* + * No .get_state callback, because the current state cannot be read + * back from the hardware. + */ +}; + +static int ntxec_pwm_probe(struct platform_device *pdev) +{ + struct ntxec *ec = dev_get_drvdata(pdev->dev.parent); + struct ntxec_pwm *priv; + struct pwm_chip *chip; + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->ec = ec; + priv->dev = &pdev->dev; + + platform_set_drvdata(pdev, priv); + + chip = &priv->chip; + chip->dev = &pdev->dev; + chip->ops = &ntxec_pwm_ops; + chip->base = -1; + chip->npwm = 1; + + return pwmchip_add(chip); +} + +static int ntxec_pwm_remove(struct platform_device *pdev) +{ + struct ntxec_pwm *priv = platform_get_drvdata(pdev); + struct pwm_chip *chip = &priv->chip; + + return pwmchip_remove(chip); +} + +static struct platform_driver ntxec_pwm_driver = { + .driver = { + .name = "ntxec-pwm", + }, + .probe = ntxec_pwm_probe, + .remove = ntxec_pwm_remove, +}; +module_platform_driver(ntxec_pwm_driver); + +MODULE_AUTHOR("Jonathan Neuschäfer "); +MODULE_DESCRIPTION("PWM driver for Netronix EC"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:ntxec-pwm");