Re: [PATCH v6] watchdog: Add DA9063 PMIC watchdog driver.

[Guenter Roeck <linux@roeck-us.net>]

On 09/08/2014 06:58 AM, Markus Pargmann wrote:
> From: Krystian Garbaciak <krystian.garbaciak@diasemi.com>
>
> This driver supports the watchdog device inside the DA9063 PMIC.
>
> Signed-off-by: Krystian Garbaciak <krystian.garbaciak@diasemi.com>
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> ---
>
> Notes:
>      Changes in v6:
>       - Fix compile error
>
>      Changes in v5:
>       - Kconfig: Add note about the module name.
>       - Change selector variables to int
>       - Style fixes
>       - use unsigned int to remove gcc verbose warning
>       - Integrate _kick() and _disable() into the calling functions
>
>      Changes in v4:
>       - Fixed indentation
>       - Fixed lock without unlock
>       - Check for parent device and device driver data in probe(). If not present,
>         this is an invalid prober initialization, return -EINVAL.
>
>      Changes in v3:
>       - Cleanup error handling for timeout selection and setting
>       - Fix race condition due to late wdt drvdata setup
>       - Remove static struct watchdog_device. It is not initialized in the probe
>         function
>       - Use WATCHDOG_NOWAYOUT_INIT_STATUS for the status
>       - Remove 0 shift using DA9063_TWDSCALE_SHIFT
>
>   drivers/watchdog/Kconfig      |   9 ++
>   drivers/watchdog/Makefile     |   1 +
>   drivers/watchdog/da9063_wdt.c | 222 ++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 232 insertions(+)
>   create mode 100644 drivers/watchdog/da9063_wdt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index f57312fced80..669de63a7a48 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -87,6 +87,15 @@ config DA9055_WATCHDOG
>   	  This driver can also be built as a module.  If so, the module
>   	  will be called da9055_wdt.
>
> +config DA9063_WATCHDOG
> +	tristate "Dialog DA9063 Watchdog"
> +	depends on MFD_DA9063
> +	select WATCHDOG_CORE
> +	help
> +	  Support for the watchdog in the DA9063 PMIC.
> +
> +	  This driver can be built as a module. The module name is da9063_wdt.
> +
>   config GPIO_WATCHDOG
>   	tristate "Watchdog device controlled through GPIO-line"
>   	depends on OF_GPIO
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 468c3204c3b1..6c467a9821fe 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -173,6 +173,7 @@ obj-$(CONFIG_XEN_WDT) += xen_wdt.o
>   # Architecture Independent
>   obj-$(CONFIG_DA9052_WATCHDOG) += da9052_wdt.o
>   obj-$(CONFIG_DA9055_WATCHDOG) += da9055_wdt.o
> +obj-$(CONFIG_DA9063_WATCHDOG) += da9063_wdt.o
>   obj-$(CONFIG_GPIO_WATCHDOG)	+= gpio_wdt.o
>   obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
>   obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
> diff --git a/drivers/watchdog/da9063_wdt.c b/drivers/watchdog/da9063_wdt.c
> new file mode 100644
> index 000000000000..88441bdd2d1b
> --- /dev/null
> +++ b/drivers/watchdog/da9063_wdt.c
> @@ -0,0 +1,222 @@
> +/*
> + * Watchdog driver for DA9063 PMICs.
> + *
> + * Copyright(c) 2012 Dialog Semiconductor Ltd.
> + *
> + * Author: Mariusz Wojtasik <mariusz.wojtasik@diasemi.com>
> + *
> + * This program is free software; you can redistribute  it and/or modify it
> + * under  the terms of  the GNU General  Public License as published by the
> + * Free Software Foundation;  either version 2 of the  License, or (at your
> + * option) any later version.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/watchdog.h>
> +#include <linux/platform_device.h>
> +#include <linux/uaccess.h>
> +#include <linux/slab.h>
> +#include <linux/delay.h>
> +#include <linux/mfd/da9063/registers.h>
> +#include <linux/mfd/da9063/core.h>
> +#include <linux/regmap.h>
> +
> +/*
> + * Watchdog selector to timeout in seconds.
> + *   0: WDT disabled;
> + *   others: timeout = 2048 ms * 2^(TWDSCALE-1).
> + */
> +static const int wdt_timeout[] = { 0, 2, 4, 8, 16, 32, 65, 131 };
> +#define DA9063_TWDSCALE_DISABLE		0
> +#define DA9063_TWDSCALE_MIN		1
> +#define DA9063_TWDSCALE_MAX		(ARRAY_SIZE(wdt_timeout) - 1)
> +#define DA9063_WDT_MIN_TIMEOUT		wdt_timeout[DA9063_TWDSCALE_MIN]
> +#define DA9063_WDT_MAX_TIMEOUT		wdt_timeout[DA9063_TWDSCALE_MAX]
> +#define DA9063_WDG_TIMEOUT		wdt_timeout[3]
> +
> +struct da9063_watchdog {
> +	struct da9063 *da9063;
> +	struct watchdog_device wdtdev;
> +	struct mutex lock;
> +};
> +
> +static int da9063_wdt_timeout_to_sel(int secs)
> +{
> +	unsigned int i;
> +
> +	for (i = DA9063_TWDSCALE_MIN; i <= DA9063_TWDSCALE_MAX; i++) {
> +		if (wdt_timeout[i] >= secs)
> +			return i;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int _da9063_wdt_set_timeout(struct da9063 *da9063, unsigned int regval)
> +{
> +	return regmap_update_bits(da9063->regmap, DA9063_REG_CONTROL_D,
> +			DA9063_TWDSCALE_MASK, regval);

Lucky you I am not the watchdog maintainer. For the hwmon drivers
I review I decided to enforce the "align continuation lines with '('"
rule after seeing the all-over-the-place indentation in this driver.

I know you explained it, but for me it is just confusing.

> +}
> +
> +static int da9063_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct da9063_watchdog *wdt = watchdog_get_drvdata(wdd);
> +	int selector;
> +	int ret;
> +
> +	selector = da9063_wdt_timeout_to_sel(wdt->wdtdev.timeout);
> +	if (selector < 0) {
> +		dev_err(wdt->da9063->dev, "Timeout out of range (timeout=%d)\n",
> +				wdt->wdtdev.timeout);

We should have a rule that error messages which can only happen if there
is a bug in the code should never be permitted ;-).

Seriously, the watchdog subsystem enforces the range, so da9063_wdt_timeout_to_sel
can never return an error. Which really means that, in case you hit that unlikely
case that da9063_wdt_timeout_to_sel gets into the error condition anyway,
a WARN_ONCE and returning DA9063_TWDSCALE_MAX there would make much more sense
than all those repeated error checks.

I come to understand that you like error checks, but please keep in mind that all
you accomplish is to increase the size of the Linux kernel with no other benefit.

> +		return selector;
> +	}
> +
> +	mutex_lock(&wdt->lock);

Wonder if this came up with this driver, or with another one.
I don't see a value in all those locks. The watchdog subsystem
already provides locking.

> +	ret = _da9063_wdt_set_timeout(wdt->da9063, selector);
> +	if (ret) {
> +		dev_err(wdt->da9063->dev, "Watchdog failed to start (err = %d)\n",
> +				ret);
> +	}

Single statement does not need { }

> +	mutex_unlock(&wdt->lock);
> +
> +	return ret;
> +}
> +
> +static int da9063_wdt_stop(struct watchdog_device *wdd)
> +{
> +	struct da9063_watchdog *wdt = watchdog_get_drvdata(wdd);
> +	int ret;
> +
> +	mutex_lock(&wdt->lock);
> +	ret = regmap_update_bits(wdt->da9063->regmap, DA9063_REG_CONTROL_D,
> +			DA9063_TWDSCALE_MASK,
> +			DA9063_TWDSCALE_DISABLE);
> +	if (ret)
> +		dev_alert(wdt->da9063->dev, "Watchdog failed to stop (err = %d)\n",
> +				ret);
> +	mutex_unlock(&wdt->lock);
> +
> +	return ret;
> +}
> +
> +static int da9063_wdt_ping(struct watchdog_device *wdd)
> +{
> +	struct da9063_watchdog *wdt = watchdog_get_drvdata(wdd);
> +	int ret;
> +
> +	mutex_lock(&wdt->lock);
> +	ret = regmap_write(wdt->da9063->regmap, DA9063_REG_CONTROL_F,
> +			DA9063_WATCHDOG);
> +	if (ret)
> +		dev_alert(wdt->da9063->dev, "Failed to ping the watchdog (err = %d)\n",
> +				ret);
> +	mutex_unlock(&wdt->lock);
> +
> +	return ret;
> +}
> +
> +static int da9063_wdt_set_timeout(struct watchdog_device *wdd,
> +		unsigned int timeout)
> +{
> +	struct da9063_watchdog *wdt = watchdog_get_drvdata(wdd);
> +	int selector;
> +	int ret;
> +
> +	selector = da9063_wdt_timeout_to_sel(timeout);
> +	if (selector < 0) {
> +		dev_err(wdt->da9063->dev,
> +				"Unsupported watchdog timeout, should be between 2 and 131\n");
> +		return -EINVAL;
> +	}
> +
> +	mutex_lock(&wdt->lock);
> +
> +	ret = _da9063_wdt_set_timeout(wdt->da9063, selector);
> +	if (ret)
> +		dev_err(wdt->da9063->dev, "Failed to set watchdog timeout (err = %d)\n",
> +				ret);
> +	else
> +		wdd->timeout = wdt_timeout[selector];
> +
> +	mutex_unlock(&wdt->lock);

The code here and in wdt_start is almost identical. Can you move it into
a single helper function, to be called with the timeout in seconds as
parameter ?

> +
> +	return ret;
> +}
> +
> +static const struct watchdog_info da9063_watchdog_info = {
> +	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
> +	.identity = "DA9063 Watchdog",
> +};
> +
> +static const struct watchdog_ops da9063_watchdog_ops = {
> +	.owner = THIS_MODULE,
> +	.start = da9063_wdt_start,
> +	.stop = da9063_wdt_stop,
> +	.ping = da9063_wdt_ping,
> +	.set_timeout = da9063_wdt_set_timeout,
> +};
> +
> +static int da9063_wdt_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	struct da9063 *da9063;
> +	struct da9063_watchdog *wdt;
> +
> +	if (!pdev->dev.parent)
> +		return -EINVAL;
> +
> +	da9063 = dev_get_drvdata(pdev->dev.parent);
> +	if (!da9063)
> +		return -EINVAL;
> +
	-ENODEV in both cases, please.

> +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	wdt->da9063 = da9063;
> +	mutex_init(&wdt->lock);
> +
> +	wdt->wdtdev.info = &da9063_watchdog_info;
> +	wdt->wdtdev.ops = &da9063_watchdog_ops;
> +	wdt->wdtdev.min_timeout = DA9063_WDT_MIN_TIMEOUT;
> +	wdt->wdtdev.max_timeout = DA9063_WDT_MAX_TIMEOUT;
> +	wdt->wdtdev.timeout = DA9063_WDG_TIMEOUT;
> +
> +	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) {
> +		dev_err(da9063->dev, "da9063-watchdog registration failed (err = %d)",

da9063-watchdog is redundant with dev_err.

> +				ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int da9063_wdt_remove(struct platform_device *pdev)
> +{
> +	struct da9063_watchdog *wdt = dev_get_drvdata(&pdev->dev);
> +
> +	watchdog_unregister_device(&wdt->wdtdev);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver da9063_wdt_driver = {
> +	.probe = da9063_wdt_probe,
> +	.remove = da9063_wdt_remove,
> +	.driver = {
> +		.name = DA9063_DRVNAME_WATCHDOG,
> +	},
> +};
> +module_platform_driver(da9063_wdt_driver);
> +
> +MODULE_AUTHOR("Mariusz Wojtasik <mariusz.wojtasik@diasemi.com>");
> +MODULE_DESCRIPTION("Watchdog driver for Dialog DA9063");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:" DA9063_DRVNAME_WATCHDOG);
>