From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 315DFCA9EB5 for ; Mon, 21 Oct 2019 07:34:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 093A92089C for ; Mon, 21 Oct 2019 07:34:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727170AbfJUHei (ORCPT ); Mon, 21 Oct 2019 03:34:38 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:46591 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726480AbfJUHei (ORCPT ); Mon, 21 Oct 2019 03:34:38 -0400 Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1iMSCs-0004Nz-0r; Mon, 21 Oct 2019 09:34:22 +0200 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1iMSCp-00056Q-OM; Mon, 21 Oct 2019 09:34:19 +0200 Date: Mon, 21 Oct 2019 09:34:19 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Jeff LaBundy Cc: lee.jones@linaro.org, dmitry.torokhov@gmail.com, jdelvare@suse.com, linux@roeck-us.net, thierry.reding@gmail.com, jic23@kernel.org, devicetree@vger.kernel.org, linux-input@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-pwm@vger.kernel.org, knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net, linux-iio@vger.kernel.org, robh+dt@kernel.org, mark.rutland@arm.com Subject: Re: [PATCH 5/8] pwm: Add support for Azoteq IQS620A PWM generator Message-ID: <20191021073419.27r4xjqpz2wswerj@pengutronix.de> References: <1571631083-4962-1-git-send-email-jeff@labundy.com> <1571631083-4962-6-git-send-email-jeff@labundy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1571631083-4962-6-git-send-email-jeff@labundy.com> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-hwmon@vger.kernel.org Sender: linux-hwmon-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org Hello Jeff, On Sun, Oct 20, 2019 at 11:11:20PM -0500, Jeff LaBundy wrote: > This patch adds support for the Azoteq IQS620A, capable of generating > a 1-kHz PWM output with duty cycle between 0.4% and 100% (inclusive). > > Signed-off-by: Jeff LaBundy > --- > drivers/pwm/Kconfig | 10 +++ > drivers/pwm/Makefile | 1 + > drivers/pwm/pwm-iqs620a.c | 167 ++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 178 insertions(+) > create mode 100644 drivers/pwm/pwm-iqs620a.c > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > index e3a2518..712445e 100644 > --- a/drivers/pwm/Kconfig > +++ b/drivers/pwm/Kconfig > @@ -222,6 +222,16 @@ config PWM_IMX_TPM > To compile this driver as a module, choose M here: the module > will be called pwm-imx-tpm. > > +config PWM_IQS620A > + tristate "Azoteq IQS620A PWM support" > + depends on MFD_IQS62X This is only a runtime dependency if I'm not mistaken, so it would be great to have depends on MFD_IQS62X || COMPILE_TEST depends on REGMAP here. > + help > + Generic PWM framework driver for the Azoteq IQS620A multi-function > + sensor. > + > + To compile this driver as a module, choose M here: the module will > + be called pwm-iqs620a. > + > config PWM_JZ4740 > tristate "Ingenic JZ47xx PWM support" > depends on MACH_INGENIC > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > index 26326ad..27c9bfa 100644 > --- a/drivers/pwm/Makefile > +++ b/drivers/pwm/Makefile > @@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG) += pwm-img.o > obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o > obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o > obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o > +obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o > obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o > obj-$(CONFIG_PWM_LP3943) += pwm-lp3943.o > obj-$(CONFIG_PWM_LPC18XX_SCT) += pwm-lpc18xx-sct.o > diff --git a/drivers/pwm/pwm-iqs620a.c b/drivers/pwm/pwm-iqs620a.c > new file mode 100644 > index 0000000..6451eb1 > --- /dev/null > +++ b/drivers/pwm/pwm-iqs620a.c > @@ -0,0 +1,167 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Azoteq IQS620A PWM Generator > + * > + * Copyright (C) 2019 > + * Author: Jeff LaBundy > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#define IQS620_PWR_SETTINGS 0xD2 > +#define IQS620_PWR_SETTINGS_PWM_OUT BIT(7) > + > +#define IQS620_PWM_DUTY_CYCLE 0xD8 > + > +#define IQS620_PWM_PERIOD_NS 1000000 > + > +struct iqs620_pwm_private { > + struct iqs62x_core *iqs62x; > + struct pwm_chip chip; > + struct notifier_block notifier; > + bool ready; This is always true, so you can drop it. > +}; > + > +static int iqs620_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, > + struct pwm_state *state) Since 71523d1812ac ("pwm: Ensure pwm_apply_state() doesn't modify the state argument") this isn't the right prototype. > +{ > + struct iqs620_pwm_private *iqs620_pwm; > + struct iqs62x_core *iqs62x; > + int error; > + int duty_calc = state->duty_cycle * 256 / IQS620_PWM_PERIOD_NS - 1; > + u8 duty_clamp = clamp(duty_calc, 0, 0xFF); > + > + iqs620_pwm = container_of(chip, struct iqs620_pwm_private, chip); > + iqs62x = iqs620_pwm->iqs62x; > + > + error = regmap_write(iqs62x->map, IQS620_PWM_DUTY_CYCLE, duty_clamp); > + if (error) > + return error; > + > + state->period = IQS620_PWM_PERIOD_NS; > + state->duty_cycle = (duty_clamp + 1) * IQS620_PWM_PERIOD_NS / 256; This suggests that if the value in the IQS620_PWM_DUTY_CYCLE is 0 the duty cycle is 1/256 ms with a period of 1 ms and the output cannot be constant inactive. If this is right please add a paragraph in the driver's comment at the top: * Limitations: * - The hardware cannot generate a 0% duty cycle (Please stick to this format, other drivers use it, too.) How does the hardware behave on changes? For example you're first committing the duty cycle and then on/off. Can it happen that between pwm_apply_state(pwm, { .duty_cycle = 3900, .period = 1000000, .enabled = true) ... pwm_apply_state(pwm, { .duty_cycle = 1000000, .period = 1000000, .enabled = false) the output is active for longer than 4 µs because the iqs620_pwm_apply function is preempted between the two register writes and so we already have .duty_cycle = 1000000 but still .enabled = true in the hardware? Does a change complete the currently running period? Does disabling complete the currently running period? If so, does regmap_update_bits block until the new setting is active? The .apply function fails to check for .pwm_polarity. You want something like: if (state->polarity != PWM_POLARITY_NORMAL) return -ENOTSUPP; (That's what pwm-rcar and the core (in the absence of .set_polarity for old-style drivers) are using. @Thierry: It would be great to fix the vaule that should be returned in this case. pwm-lpss and sifive use -EINVAL.) > + return regmap_update_bits(iqs62x->map, IQS620_PWR_SETTINGS, > + IQS620_PWR_SETTINGS_PWM_OUT, > + state->enabled ? 0xFF : 0); > +} > + > +static int iqs620_pwm_notifier(struct notifier_block *notifier, > + unsigned long event_flags, void *context) > +{ > + struct iqs620_pwm_private *iqs620_pwm; > + struct pwm_state state; > + int error; > + > + iqs620_pwm = container_of(notifier, struct iqs620_pwm_private, > + notifier); > + > + if (!iqs620_pwm->ready || !(event_flags & BIT(IQS62X_EVENT_SYS_RESET))) > + return NOTIFY_DONE; > + > + pwm_get_state(&iqs620_pwm->chip.pwms[0], &state); > + > + error = iqs620_pwm_apply(&iqs620_pwm->chip, > + &iqs620_pwm->chip.pwms[0], &state); > + if (error) { > + dev_err(iqs620_pwm->chip.dev, > + "Failed to re-initialize device: %d\n", error); > + return NOTIFY_BAD; > + } > + > + return NOTIFY_OK; So the PWM can loose it's state sometimes? When does that happen? > +} > + > +static void iqs620_pwm_notifier_unregister(void *context) > +{ > + struct iqs620_pwm_private *iqs620_pwm = context; > + int error; > + > + error = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh, > + &iqs620_pwm->notifier); > + if (error) > + dev_err(iqs620_pwm->chip.dev, > + "Failed to unregister notifier: %d\n", error); > +} > + > +static const struct pwm_ops iqs620_pwm_ops = { > + .apply = iqs620_pwm_apply, Please implement a .get_state callback. > + .owner = THIS_MODULE, > +}; > + > +static int iqs620_pwm_probe(struct platform_device *pdev) > +{ > + struct iqs620_pwm_private *iqs620_pwm; > + int error; > + > + iqs620_pwm = devm_kzalloc(&pdev->dev, sizeof(*iqs620_pwm), GFP_KERNEL); > + if (!iqs620_pwm) > + return -ENOMEM; > + > + platform_set_drvdata(pdev, iqs620_pwm); > + iqs620_pwm->iqs62x = dev_get_drvdata(pdev->dev.parent); > + > + iqs620_pwm->chip.dev = &pdev->dev; > + iqs620_pwm->chip.ops = &iqs620_pwm_ops; > + iqs620_pwm->chip.base = -1; > + iqs620_pwm->chip.npwm = 1; > + > + iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier; > + error = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh, > + &iqs620_pwm->notifier); > + if (error) { > + dev_err(&pdev->dev, "Failed to register notifier: %d\n", error); > + return error; > + } > + > + error = devm_add_action_or_reset(&pdev->dev, > + iqs620_pwm_notifier_unregister, > + iqs620_pwm); I wonder if this is safe. If in iqs620_pwm_notifier_unregister() unregistering of the notifier goes wrong (not sure when this can happen) the memory behind iqs620_pwm goes away. Then later iqs620_pwm_notifier might be called trying to use *iqs620_pwm ... > + if (error) { > + dev_err(&pdev->dev, "Failed to add action: %d\n", error); > + return error; > [...] > > +static struct platform_driver iqs620_pwm_platform_driver = { > + .driver = { > + .name = IQS620_DRV_NAME_PWM, > + }, > + .probe = iqs620_pwm_probe, > + .remove = iqs620_pwm_remove, > +}; I'm not a big fan of aligning the = in struct initializers. The downside is that if you later add .prevent_deferred_probe = true, you either have to touch all (otherwise unrelated) lines to realign which adds churn, or the structure is only partially aligned which looks ugly. That's why I stick to a single space before the =. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |