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Subject: Re: [PATCH 8/8] watchdog: stpmu1: add stpmu1 watchdog driver
To:     Pascal PAILLET-LME <p.paillet@st.com>,
        "dmitry.torokhov@gmail.com" <dmitry.torokhov@gmail.com>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "lee.jones@linaro.org" <lee.jones@linaro.org>,
        "lgirdwood@gmail.com" <lgirdwood@gmail.com>,
        "broonie@kernel.org" <broonie@kernel.org>,
        "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
        "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
        "benjamin.gaignard@linaro.org" <benjamin.gaignard@linaro.org>
References: <1530803657-17684-1-git-send-email-p.paillet@st.com>
 <1530803657-17684-9-git-send-email-p.paillet@st.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <ade05366-ce30-f643-7111-f3d24378df63@roeck-us.net>
Date:   Thu, 5 Jul 2018 11:48:53 -0700
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On 07/05/2018 08:14 AM, Pascal PAILLET-LME wrote:
> From: pascal paillet <p.paillet@st.com>
> 
> The stpmu1 PMIC embeds a watchdog which is disabled by default. As soon
> as the watchdog is started, it must be refreshed periodically otherwise
> the PMIC goes off.
> 
> Signed-off-by: pascal paillet <p.paillet@st.com>
> ---
>   drivers/watchdog/Kconfig      |  12 +++
>   drivers/watchdog/Makefile     |   1 +
>   drivers/watchdog/stpmu1_wdt.c | 177 ++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 190 insertions(+)
>   create mode 100644 drivers/watchdog/stpmu1_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 9af07fd..2155f4d 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -796,6 +796,18 @@ config STM32_WATCHDOG
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called stm32_iwdg.
>   
> +config STPMU1_WATCHDOG
> +	tristate "STPMU1 PMIC watchdog support"
> +	depends on MFD_STPMU1
> +	select WATCHDOG_CORE
> +	help
> +	  Say Y here to include watchdog support embedded into STPMU1 PMIC.
> +	  If the watchdog timer expires, stpmu1 shut-down all its power
> +	  supplies.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called spmu1_wdt.
> +
>   config UNIPHIER_WATCHDOG
>   	tristate "UniPhier watchdog support"
>   	depends on ARCH_UNIPHIER || COMPILE_TEST
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 1d3c6b0..c9eba94 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -216,3 +216,4 @@ obj-$(CONFIG_ZIIRAVE_WATCHDOG) += ziirave_wdt.o
>   obj-$(CONFIG_SOFT_WATCHDOG) += softdog.o
>   obj-$(CONFIG_MENF21BMC_WATCHDOG) += menf21bmc_wdt.o
>   obj-$(CONFIG_RAVE_SP_WATCHDOG) += rave-sp-wdt.o
> +obj-$(CONFIG_STPMU1_WATCHDOG) += stpmu1_wdt.o
> diff --git a/drivers/watchdog/stpmu1_wdt.c b/drivers/watchdog/stpmu1_wdt.c
> new file mode 100644
> index 0000000..57e0afa
> --- /dev/null
> +++ b/drivers/watchdog/stpmu1_wdt.c
> @@ -0,0 +1,177 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) STMicroelectronics 2018 - All Rights Reserved
> + * Author: Philippe Peurichard <philippe.peurichard@st.com>,
> + * Pascal Paillet <p.paillet@st.com> for STMicroelectronics.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/mfd/stpmu1.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/regmap.h>
> +#include <linux/reboot.h>
> +#include <linux/slab.h>
> +#include <linux/watchdog.h>
> +
> +/* WATCHDOG CONTROL REGISTER bit */
> +#define WDT_START		BIT(0)
> +#define WDT_PING		BIT(1)
> +#define WDT_START_MASK		BIT(0)
> +#define WDT_PING_MASK		BIT(1)
> +
> +#define PMIC_WDT_MIN_TIMEOUT 1
> +#define PMIC_WDT_MAX_TIMEOUT 256
> +
> +struct stpmu1_wdt {
> +	struct stpmu1_dev *pmic;
> +	struct watchdog_device wdtdev;
> +	struct notifier_block restart_handler;
> +};
> +
> +static int pmic_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct stpmu1_wdt *wdt = watchdog_get_drvdata(wdd);
> +
> +	return regmap_update_bits(wdt->pmic->regmap,
> +				  WCHDG_CR, WDT_START_MASK, WDT_START);
> +}
> +
> +static int pmic_wdt_stop(struct watchdog_device *wdd)
> +{
> +	struct stpmu1_wdt *wdt = watchdog_get_drvdata(wdd);
> +
> +	return regmap_update_bits(wdt->pmic->regmap,
> +				  WCHDG_CR, WDT_START_MASK, ~WDT_START);
> +}
> +
> +static int pmic_wdt_ping(struct watchdog_device *wdd)
> +{
> +	struct stpmu1_wdt *wdt = watchdog_get_drvdata(wdd);
> +	int ret;
> +
> +	return regmap_update_bits(wdt->pmic->regmap,
> +				  WCHDG_CR, WDT_PING_MASK, WDT_PING);
> +	return ret;
> +}
> +
> +static int pmic_wdt_set_timeout(struct watchdog_device *wdd,
> +				unsigned int timeout)
> +{
> +	struct stpmu1_wdt *wdt = watchdog_get_drvdata(wdd);
> +	int ret;
> +
> +	ret = regmap_write(wdt->pmic->regmap, WCHDG_TIMER_CR, timeout);
> +	if (ret)
> +		dev_err(wdt->pmic->dev,
> +			"Failed to set watchdog timeout (err = %d)\n", ret);
> +	else
> +		wdd->timeout = PMIC_WDT_MAX_TIMEOUT;

First the requested timeout is set, then the caller is notified
that the timeout was set to the maximum possible value ? That doesn't
make sense. If that is really intentional, I would expect a detailed
explanation, and I would expect that the value written into the chip
register matches the value reported back to the user.

> +
> +	return ret;
> +}
> +
> +static int pmic_wdt_restart_handler(struct notifier_block *this,
> +				    unsigned long mode, void *cmd)
> +{
> +	struct stpmu1_wdt *wdt = container_of(this,
> +						   struct stpmu1_wdt,
> +						   restart_handler);
> +
> +	dev_info(wdt->pmic->dev,
> +		 "PMIC Watchdog Elapsed (timeout %d), shutdown of PMIC initiated\n",
> +		 wdt->wdtdev.timeout);
> +

Register a restart handler just to issue a message ? That is quite pointless.
A restart handler is supposed to restart the system. Besides, the message
is highly misleading; there is no reason to believe that it will be called
after the watchdog expired.

This function should restart the system. If it doesn't, drop it.

> +	return NOTIFY_DONE;
> +}
> +
> +static const struct watchdog_info pmic_watchdog_info = {
> +	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
> +	.identity = "STPMU1 PMIC Watchdog",
> +};
> +
> +static const struct watchdog_ops pmic_watchdog_ops = {
> +	.owner = THIS_MODULE,
> +	.start = pmic_wdt_start,
> +	.stop = pmic_wdt_stop,
> +	.ping = pmic_wdt_ping,
> +	.set_timeout = pmic_wdt_set_timeout,
> +};
> +
> +static int pmic_wdt_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	struct stpmu1_dev *pmic;
> +	struct stpmu1_wdt *wdt;
> +
> +	if (!pdev->dev.parent)
> +		return -EINVAL;
> +
> +	pmic = dev_get_drvdata(pdev->dev.parent);
> +	if (!pmic)
> +		return -EINVAL;
> +
> +	wdt = devm_kzalloc(&pdev->dev, sizeof(struct stpmu1_wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	wdt->pmic = pmic;
> +
> +	wdt->wdtdev.info = &pmic_watchdog_info;
> +	wdt->wdtdev.ops = &pmic_watchdog_ops;
> +	wdt->wdtdev.min_timeout = PMIC_WDT_MIN_TIMEOUT;
> +	wdt->wdtdev.max_timeout = PMIC_WDT_MAX_TIMEOUT;
> +	wdt->wdtdev.timeout = PMIC_WDT_MAX_TIMEOUT;

256 seconds default timeout ? Unusual, just making sure that this is what you want.

> +
> +	wdt->wdtdev.status = WATCHDOG_NOWAYOUT_INIT_STATUS;
> +
> +	watchdog_set_drvdata(&wdt->wdtdev, wdt);
> +	dev_set_drvdata(&pdev->dev, wdt);
> +
> +	ret = watchdog_register_device(&wdt->wdtdev);
> +	if (ret)
> +		return ret;
> +
> +	wdt->restart_handler.notifier_call = pmic_wdt_restart_handler;
> +	wdt->restart_handler.priority = 128;
> +	ret = register_restart_handler(&wdt->restart_handler);

Why is the restart handler provided by the watchdog core not sufficient ?


> +	if (ret) {
> +		dev_err(wdt->pmic->dev, "failed to register restart handler\n");
> +		return ret;
> +	}
> +
> +	dev_dbg(wdt->pmic->dev, "PMIC Watchdog driver probed\n");

The only reasons not to use the devm_ function to register the watchdog
are the restart handler, which 1) doesn't do anything and 2) should use
the watchdog core, and this debug message. I would suggest to use the
devm_ function to register the watchdog instead.

> +	return 0;
> +}
> +
> +static int pmic_wdt_remove(struct platform_device *pdev)
> +{
> +	struct stpmu1_wdt *wdt = dev_get_drvdata(&pdev->dev);
> +
> +	unregister_restart_handler(&wdt->restart_handler);
> +	watchdog_unregister_device(&wdt->wdtdev);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id of_pmic_wdt_match[] = {
> +	{ .compatible = "st,stpmu1-wdt" },
> +	{ },
> +};
> +
> +MODULE_DEVICE_TABLE(of, of_pmic_wdt_match);
> +
> +static struct platform_driver stpmu1_wdt_driver = {
> +	.probe = pmic_wdt_probe,
> +	.remove = pmic_wdt_remove,
> +	.driver = {
> +		.name = "stpmu1-wdt",
> +		.of_match_table = of_pmic_wdt_match,
> +	},
> +};
> +module_platform_driver(stpmu1_wdt_driver);
> +
> +MODULE_AUTHOR("philippe.peurichard@st.com>");
> +MODULE_DESCRIPTION("Watchdog driver for STPMU1 device");
> +MODULE_LICENSE("GPL");
>