Re: [PATCH v2 2/4] ARM: meson: add watchdog driver

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

On 09/17/2014 01:12 PM, Carlo Caione wrote:
> This patch adds the watchdog driver for the Amlogic Meson SoCs used also
> to reboot the device.
>
> Signed-off-by: Carlo Caione <carlo@caione.org>
> ---
>   drivers/watchdog/Kconfig     |  10 ++
>   drivers/watchdog/Makefile    |   1 +
>   drivers/watchdog/meson_wdt.c | 237 +++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 248 insertions(+)
>   create mode 100644 drivers/watchdog/meson_wdt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index f57312f..836cb00 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -443,6 +443,16 @@ config TEGRA_WATCHDOG
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called tegra_wdt.
>
> +config MESON_WATCHDOG
> +	tristate "Amlogic Meson SoCs watchdog support"
> +	depends on ARCH_MESON
> +	select WATCHDOG_CORE
> +	help
> +	  Say Y here to include support for the watchdog timer
> +	  in Amlogic Meson SoCs.
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called meson_wdt.
> +
>   # AVR32 Architecture
>
>   config AT32AP700X_WDT
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 468c320..e7a9259 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -59,6 +59,7 @@ obj-$(CONFIG_MOXART_WDT) += moxart_wdt.o
>   obj-$(CONFIG_SIRFSOC_WATCHDOG) += sirfsoc_wdt.o
>   obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
>   obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
> +obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
>
>   # AVR32 Architecture
>   obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
> diff --git a/drivers/watchdog/meson_wdt.c b/drivers/watchdog/meson_wdt.c
> new file mode 100644
> index 0000000..3fbe147
> --- /dev/null
> +++ b/drivers/watchdog/meson_wdt.c
> @@ -0,0 +1,237 @@
> +/*
> + *      Meson Watchdog Driver
> + *
> + *      Copyright (c) 2014 Carlo Caione
> + *
> + *      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/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/notifier.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reboot.h>
> +#include <linux/types.h>
> +#include <linux/watchdog.h>
> +
> +#define DRV_NAME		"meson_wdt"
> +
> +#define MESON_WDT_TC		0x00
> +#define MESON_WDT_TC_EN		BIT(22)
> +#define MESON_WDT_TC_TM_MASK	0x3fffff
> +#define MESON_WDT_DC_RESET	(3 << 24)
> +
> +#define MESON_WDT_RESET		0x04
> +
Does this all use the same indentation ? Looks a bit odd.

> +#define MESON_WDT_TIMEOUT	40
> +#define MESON_WDT_MIN_TIMEOUT	1
> +#define MESON_WDT_MAX_TIMEOUT	30
> +

Default timeout is 40 seconds, maximum timeout is 30 seconds ?
That doesn't really make much sense. What is the real maximum timeout ?
If it is 0x3fffff / 100000, as the code suggests, you should set
MAX_TIMEOUT to 41 or possibly (0x3fffff / 100000) so people understand
what is going on.

> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +static unsigned int timeout = MESON_WDT_TIMEOUT;
> +
> +struct meson_wdt_dev {
> +	struct watchdog_device wdt_dev;
> +	void __iomem *wdt_base;
> +	struct notifier_block restart_handler;
> +};
> +
> +static int meson_restart_handle(struct notifier_block *this, unsigned long mode,
> +				void *cmd)
> +{
> +	u32 tc_reboot = MESON_WDT_DC_RESET | MESON_WDT_TC_EN | 100;

What does the magic 100 do ?

> +	struct meson_wdt_dev *meson_wdt = container_of(this,
> +						       struct meson_wdt_dev,
> +						       restart_handler);
> +
> +	writel(tc_reboot, meson_wdt->wdt_base + MESON_WDT_TC);
> +	writel(0, meson_wdt->wdt_base + MESON_WDT_RESET);
> +
Is this sequence necessary ? Just asking, looks a bit odd.

> +	while (1) {
> +		mdelay(5);
> +		writel(tc_reboot, meson_wdt->wdt_base + MESON_WDT_TC);
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static int meson_wdt_ping(struct watchdog_device *wdt_dev)
> +{
> +	struct meson_wdt_dev *meson_wdt = watchdog_get_drvdata(wdt_dev);
> +
> +	writel(0, meson_wdt->wdt_base + MESON_WDT_RESET);
> +
> +	return 0;
> +}
> +
> +static int meson_wdt_set_timeout(struct watchdog_device *wdt_dev,
> +				 unsigned int timeout)
> +{
> +	struct meson_wdt_dev *meson_wdt = watchdog_get_drvdata(wdt_dev);
> +	u32 reg;
> +
> +	meson_wdt->wdt_dev.timeout = timeout;
> +
> +	reg = readl(meson_wdt->wdt_base + MESON_WDT_TC);
> +	reg &= ~MESON_WDT_TC_TM_MASK;
> +	reg |= (timeout * 100 * 1000);

A define for the clock rate might be helpful.

> +	writel(reg, meson_wdt->wdt_base + MESON_WDT_TC);
> +
> +	meson_wdt_ping(wdt_dev);
> +
> +	return 0;
> +}
> +
> +static int meson_wdt_stop(struct watchdog_device *wdt_dev)
> +{
> +	struct meson_wdt_dev *meson_wdt = watchdog_get_drvdata(wdt_dev);
> +	u32 reg;
> +
> +	writel(0, meson_wdt->wdt_base + MESON_WDT_RESET);

Is this final ping really needed here ?

> +	reg = readl(meson_wdt->wdt_base + MESON_WDT_TC);
> +	reg &= ~MESON_WDT_TC_EN;
> +	writel(reg, meson_wdt->wdt_base + MESON_WDT_TC);
> +
> +	return 0;
> +}
> +
> +static int meson_wdt_start(struct watchdog_device *wdt_dev)
> +{
> +	struct meson_wdt_dev *meson_wdt = watchdog_get_drvdata(wdt_dev);
> +	u32 reg;
> +	int ret;
> +
> +	ret = meson_wdt_set_timeout(&meson_wdt->wdt_dev,
> +				    meson_wdt->wdt_dev.timeout);

Not really sure if that is such a good idea here, as the set_timeout
function does a bit more than just writing the timeout into the register.
If you don't want to hard-code it here, I would suggest to write a
little helper function which only writes it into the register
(which would be called from both here and from meson_wdt_set_timeout).

> +	if (ret < 0)
> +		return ret;
> +
> +	writel(0, meson_wdt->wdt_base + MESON_WDT_RESET);
> +	reg = readl(meson_wdt->wdt_base + MESON_WDT_TC);
> +	reg |= MESON_WDT_TC_EN;
> +	writel(reg, meson_wdt->wdt_base + MESON_WDT_TC);
> +
> +	return 0;
> +}
> +
> +static const struct watchdog_info meson_wdt_info = {
> +	.identity	= DRV_NAME,
> +	.options	= WDIOF_SETTIMEOUT |
> +			  WDIOF_KEEPALIVEPING |
> +			  WDIOF_MAGICCLOSE,
> +};
> +
> +static const struct watchdog_ops meson_wdt_ops = {
> +	.owner		= THIS_MODULE,
> +	.start		= meson_wdt_start,
> +	.stop		= meson_wdt_stop,
> +	.ping		= meson_wdt_ping,
> +	.set_timeout	= meson_wdt_set_timeout,
> +};
> +
> +static int meson_wdt_probe(struct platform_device *pdev)
> +{
> +	struct resource *res;
> +	struct meson_wdt_dev *meson_wdt;
> +	int err;
> +
> +	meson_wdt = devm_kzalloc(&pdev->dev, sizeof(*meson_wdt), GFP_KERNEL);
> +	if (!meson_wdt)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	meson_wdt->wdt_base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(meson_wdt->wdt_base))
> +		return PTR_ERR(meson_wdt->wdt_base);
> +
> +	meson_wdt->wdt_dev.parent = &pdev->dev;
> +	meson_wdt->wdt_dev.info = &meson_wdt_info;
> +	meson_wdt->wdt_dev.ops = &meson_wdt_ops;
> +	meson_wdt->wdt_dev.timeout = MESON_WDT_TIMEOUT;
> +	meson_wdt->wdt_dev.max_timeout = MESON_WDT_MAX_TIMEOUT;
> +	meson_wdt->wdt_dev.min_timeout = MESON_WDT_MIN_TIMEOUT;
> +
> +	watchdog_set_drvdata(&meson_wdt->wdt_dev, meson_wdt);
> +
> +	watchdog_init_timeout(&meson_wdt->wdt_dev, timeout, &pdev->dev);
> +	watchdog_set_nowayout(&meson_wdt->wdt_dev, nowayout);
> +
> +	meson_wdt_stop(&meson_wdt->wdt_dev);
> +
> +	err = watchdog_register_device(&meson_wdt->wdt_dev);
> +	if (unlikely(err))
> +		return err;

Please drop the unlikely.

> +
> +	platform_set_drvdata(pdev, meson_wdt);
> +
> +	meson_wdt->restart_handler.notifier_call = meson_restart_handle;
> +	meson_wdt->restart_handler.priority = 128;
> +	err = register_restart_handler(&meson_wdt->restart_handler);
> +	if (err)
> +		dev_err(&pdev->dev,
> +			"cannot register restart handler (err=%d)\n", err);
> +
> +	dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)",
> +		 meson_wdt->wdt_dev.timeout, nowayout);
> +
> +	return 0;
> +}
> +
> +static int meson_wdt_remove(struct platform_device *pdev)
> +{
> +	struct meson_wdt_dev *meson_wdt = platform_get_drvdata(pdev);
> +
> +	unregister_restart_handler(&meson_wdt->restart_handler);
> +
> +	watchdog_unregister_device(&meson_wdt->wdt_dev);
> +	watchdog_set_drvdata(&meson_wdt->wdt_dev, NULL);

Unnecessary.

> +
> +	return 0;
> +}
> +
> +static void meson_wdt_shutdown(struct platform_device *pdev)
> +{
> +	struct meson_wdt_dev *meson_wdt = platform_get_drvdata(pdev);
> +
> +	meson_wdt_stop(&meson_wdt->wdt_dev);
> +}
> +
> +static const struct of_device_id meson_wdt_dt_ids[] = {
> +	{ .compatible = "amlogic,meson-wdt" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, meson_wdt_dt_ids);
> +
> +static struct platform_driver meson_wdt_driver = {
> +	.probe		= meson_wdt_probe,
> +	.remove		= meson_wdt_remove,
> +	.shutdown	= meson_wdt_shutdown,
> +	.driver		= {
> +		.owner		= THIS_MODULE,
> +		.name		= DRV_NAME,
> +		.of_match_table	= meson_wdt_dt_ids,
> +	},
> +};
> +
> +module_platform_driver(meson_wdt_driver);
> +
> +module_param(timeout, uint, 0);
> +MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
> +
> +module_param(nowayout, bool, 0);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
> +		"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Carlo Caione <carlo@caione.org>");
> +MODULE_DESCRIPTION("Meson Watchdog Timer Driver");
>