From patchwork Sat Jan 16 19:48:23 2021 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: 1427574 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; dkim=pass (1024-bit key; secure) header.d=gmx.net header.i=@gmx.net header.a=rsa-sha256 header.s=badeba3b8450 header.b=KiJ+6HQi; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4DJ9My2wpQz9sWF for ; Sun, 17 Jan 2021 07:57:02 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727317AbhAPU4f (ORCPT ); Sat, 16 Jan 2021 15:56:35 -0500 Received: from mout.gmx.net ([212.227.15.19]:57627 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726788AbhAPU4N (ORCPT ); Sat, 16 Jan 2021 15:56:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1610830430; bh=CNBRA+c+NY/9LumPB+UY4n0iAV9NlGywmp537B5vKd8=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date:In-Reply-To:References; b=KiJ+6HQi0sh/5TcrGBksGevwJEAa39i2VCGib66pvYjsdlC1QSDp7m2NPRGzToIAM hRBYh2rB4z6qo7ACn12LzjY+QB7goGWLUZxkaZh5IT5MX2l9JJ4rq1t8xxefHDbxXP TXzEQ8M0WJLnihZ7FiqWA4OCyM23fnyPSeaI37Vo= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from longitude ([37.201.215.209]) by mail.gmx.com (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1Mkpf3-1llXGr29q3-00mHL8; Sat, 16 Jan 2021 21:53:50 +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 v8 4/7] pwm: ntxec: Add driver for PWM function in Netronix EC Date: Sat, 16 Jan 2021 20:48:23 +0100 Message-Id: <20210116194826.3866540-5-j.neuschaefer@gmx.net> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210116194826.3866540-1-j.neuschaefer@gmx.net> References: <20210116194826.3866540-1-j.neuschaefer@gmx.net> MIME-Version: 1.0 X-Provags-ID: V03:K1:sR0d3iqo8IyQZSTjKPwyjcol376hsZD6Y/nteZGtp/f6UWwNUfn 4UICbrr4QpIG3aUq8auyoRBckRdFWzg+sG8RFmnf/0IxP0wmoA4tZQemZ3dsqgqRW2o14fi I8aPDY+ijTb03qU1koS3VASpaAYb9qphVjur4vq1H/OCvWUKlPl1P8mlfoW4Gkt8UtlTQc0 2dScoDyVg8xEv1vdcz3uQ== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:AL4DOgyui78=:C8UVbU7Z4sDYtGu3aOjPpN LhHzT6kWMYSxJmRm7ED8GJa4yamikvi9OZvM6HqXVGSjxd8klRRQ3UjKpwI7PPz8eSYuI5hMs sH95aVzKWor6v8tRAU0CUusoSw7lu0U8PtRqWjqUITQ9o7/7QPbxuPxrlPCcXmSJ8Fsj5t3L8 PQ5ltcEcl+GCQ65CfeG0o3dcCyT2cVgLKhVJQ6vFAVlKH2BO2xnWbmTntA9lDI1eyGWL4GmuX qjTQ/ukymFL/lGJbDa81sBb33g2xm5TcfRos3pYFxCtWD9DS3QiuFyv0kvEyQ0Mz0SODsNv3k TJsJWqZAZ78jpFTxWfijoV3UfS9w1/vLkCXK0A4Rrm6C2N7aax9FxCfzAjQs2L6hGTu50bLTA XZS8QcmroRmEXos4eyvcxywaBslyAFZGuecbo744IXakFXBXXyzl1O4Y16/B/JDpEH1etr5uN IhDAsFBWzKQsPekso8RiEgvj5D56bbYlTKnYmp40Oh46tETIRZ1olBYdlo2vY/5+nDgETP3QF /7MBPn5j/+1+vd49QCmYppNGQ02Uap1HQxkB3f3/7OSFt/v6mObTiQGtNi06mPhiWKrzha4iC xpmDhqUz5SFPNHVN3jpqAJLb3NK8JgUFEQ3urPDACNr9GVDVtJblQKD/qekLQlxmOLavRBbs8 Xq13UPa+UXeG9QhnAW8mh0zl8GFPQudJH1zF+ahpgcMh6GcWEHiJNxHPb7S9/kFWacPDImWbA 5Ruc85iPSIssEHyZSOnbaMCf2yQGaQZd/EUOqcoMA2ufSXwNb3BoGeXY23Of57lVhtsTpKjIC WiTfA+uEbj5/ozndy6Ey2oScDOFndEQ08nsUkSO4KV2sPM5qD/0hz/8zGqLN/ulULkcgNFPvM JYZLgX/6k+PzfFSnuqcQ== 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 Reviewed-by: Uwe Kleine-König Acked-by: Thierry Reding --- v8: - Add Uwe Kleine-König's R-b tag - Copy dev.of_node from parent device v7: - no changes v6: - https://lore.kernel.org/lkml/20201208011000.3060239-5-j.neuschaefer@gmx.net/ - 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 | 184 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 193 insertions(+) create mode 100644 drivers/pwm/pwm-ntxec.c -- 2.29.2 diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 0937e1c047acb..a2830b8832b97 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -393,6 +393,14 @@ 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 18b89d7fd092a..7d97eb595bbef 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -35,6 +35,7 @@ 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..50c454c553c46 --- /dev/null +++ b/drivers/pwm/pwm-ntxec.c @@ -0,0 +1,184 @@ +// 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; + + pdev->dev.of_node = pdev->dev.parent->of_node; + + 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");