From patchwork Tue Dec 8 01:09:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?J=2E_Neusch=C3=A4fer?= X-Patchwork-Id: 1412398 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-pwm-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmx.net Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=gmx.net header.i=@gmx.net header.a=rsa-sha256 header.s=badeba3b8450 header.b=GpOxOKaz; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4CqkJ62Jlvz9s0b for ; Tue, 8 Dec 2020 13:13:58 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727863AbgLHCNN (ORCPT ); Mon, 7 Dec 2020 21:13:13 -0500 Received: from mout.gmx.net ([212.227.17.22]:47989 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727179AbgLHCNM (ORCPT ); Mon, 7 Dec 2020 21:13:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1607393448; bh=3bUR5RteUD84SV4r5mV8wbesUNH5mHlrCIlD61Ezsb8=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date:In-Reply-To:References; b=GpOxOKazJK2drKKsnFN1u0m80/I6HOd+1jHzm4pGyCJnZj3/rUm9HxFssVb7W00HP yK5ttwZCmP8bDEzR6Vy3g0yy32Juxm+xPo57GpZwhUY/k5Ikt6blNQU0k0yB1Vn+20 6dlQp4U6J4AV1szC67bJrYf2ymDc6ffuvcJyrhZY= 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 1MxUnp-1jxxNR2RZ3-00xow7; Tue, 08 Dec 2020 03:10:48 +0100 From: =?utf-8?q?Jonathan_Neusch=C3=A4fer?= To: linux-kernel@vger.kernel.org Cc: Lee Jones , Rob Herring , =?utf-8?q?Jonathan_Neusch=C3=A4fer?= , Thierry Reding , =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , Alessandro Zummo , Alexandre Belloni , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , Sam Ravnborg , Linus Walleij , Heiko Stuebner , Stephan Gerhold , Lubomir Rintel , Mark Brown , allen , Mauro Carvalho Chehab , "David S. Miller" , devicetree@vger.kernel.org, linux-pwm@vger.kernel.org, linux-rtc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Heiko Stuebner , Josua Mayer , Andreas Kemnade , Arnd Bergmann , Daniel Palmer , Andy Shevchenko Subject: [PATCH v6 4/7] pwm: ntxec: Add driver for PWM function in Netronix EC Date: Tue, 8 Dec 2020 02:09:57 +0100 Message-Id: <20201208011000.3060239-5-j.neuschaefer@gmx.net> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201208011000.3060239-1-j.neuschaefer@gmx.net> References: <20201208011000.3060239-1-j.neuschaefer@gmx.net> MIME-Version: 1.0 X-Provags-ID: V03:K1:lWxKGJoo4ovv72PsBhWyfkQEz3XncuYbVKUdDerj9SxbRXx8cEs BRwsimzOE9o9dmHlfjjMFMzYB0r7qixz9FIKhD4v83QmpzWRfCOeKUlsjP+WUM/OAuT1QTt C+BHt0HbNEHJM65wvTipykCkfAG1FsNP3wq9hdE5GBRzaLtMotlNLW+nN0XntQc+zbtw6vP +BHQ9+l23JMbVeMfzk8ag== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:MCDXIrndLd4=:SHndr/Vcwfw55Ey8iZdX6x gMhcVeCi9cQd0sRhhWhp9TYyXYAn9+rgSzMzqF09W/M0uLS/UeZIUc48lwioaiEKQerPR3JpX YDAJ/aPg30K06hz8Xy/laOoHVG+Fqt2nLfzmSOBM54+UnZFMRcQVkfdiT0WY+Yam2+w8RPzuT djFpbu2HAir/XoHIZeKrtIdzqxCjhYYAz9XxqCFY9BBeXVGtzluveWkTpp3Sv0p1WSjqort8W TeZSrDmGLDkY+l+xJUBhm0Xxhbg/uEGMGoZ5AdIr02eUOynQYO67PHijbe5kebLu0lc8znCyD pI8yIgcUSYnc8/vOkve3hbmnotFNaNamRnHZKnfkAe7MqhZHjU0V/dEidtNZZZHELvhgWPGbp PfSYNOIBT7zPQvIRFHTU9pEnkAZdFRpzYagKGhTQPmT1ng36beJA6v3PpItBTwCq7nCFgvqaG /IoqD+etNDP+M7OJ3tzER3wUmR++btoNj6YhJtk+Ek1mxNIaeZ3RrHwD9vMSsr00DArbYHiWB PTFz8dG4xQDRq1K00C0hyNhn0R8izVk9WjTAEWnsLI8zo0XsUt/a+egFaqGFWo1qoQCAjl4Cx Yp/eFXhvuGfKfI6H+8k9zOdyrtJb8vpgCP8lGF2nx6ayueh5xfOVyBl6eBJbg5bcmvfaiP6Ov JN18PyI5vWm820X5zIXj6j8fIKAiXEJArbuCzp37igD+KAD64v23qi9jFTFE7KbfjnoxUq083 X3ApuezylOD6nTVTfMGOX7/U5sORgquFGIbGRxUijDEuPC2mKtTvetXd6UIDA7agflkubnpEr J7qKgdvEo/pOg5TOO0ZkC8CBNgRNJoyCyvoWK5jFQAMM8edL5v+O6GEpd7NUcOaHi1VRicrTl 3URRkx2be8sFjmbxKgVQ== Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.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 --- v6: - Move period / duty cycle setting code to a function - Rename pwmchip_to_priv to ntxec_pwm_from_chip - Set period and duty cycle only before enabling the output - Mention that duty=0, enable=1 is assumed not to happen - Interleave writes to the period and duty cycle registers, to minimize the window of time that an inconsistent state is configured v5: - https://lore.kernel.org/lkml/20201201011513.1627028-5-j.neuschaefer@gmx.net/ - 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 | 182 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 191 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..1db30a6caa3ad --- /dev/null +++ b/drivers/pwm/pwm-ntxec.c @@ -0,0 +1,182 @@ +// 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 *ntxec_pwm_from_chip(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_set_raw_period_and_duty_cycle(struct pwm_chip *chip, + int period, int duty) +{ + struct ntxec_pwm *priv = ntxec_pwm_from_chip(chip); + + /* + * 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. + * + * To minimize the time between the changes to period and duty cycle + * taking effect, the writes are interleaved. + */ + + struct reg_sequence regs[] = { + { NTXEC_REG_PERIOD_HIGH, ntxec_reg8(period >> 8) }, + { NTXEC_REG_DUTY_HIGH, ntxec_reg8(duty >> 8) }, + { NTXEC_REG_PERIOD_LOW, ntxec_reg8(period) }, + { NTXEC_REG_DUTY_LOW, ntxec_reg8(duty) }, + }; + + return regmap_multi_reg_write(priv->ec->regmap, regs, ARRAY_SIZE(regs)); +} + +static int ntxec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm_dev, + const struct pwm_state *state) +{ + struct ntxec_pwm *priv = ntxec_pwm_from_chip(chip); + unsigned int period, duty; + 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; + + /* + * 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. + * The case that something has previously set the duty cycle to zero + * but ENABLE=1, is not handled. + */ + if (state->enabled && duty != 0) { + res = ntxec_pwm_set_raw_period_and_duty_cycle(chip, period, duty); + if (res) + return res; + + 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");