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SubjectRe: [PATCH 3/3] watchdog: bcm2835_wdt: set WDOG_HW_RUNNING bit when appropriate
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On 07/15/2016 01:15 AM, Rasmus Villemoes wrote:
> A bootloader may start the watchdog device before handing control to
> the kernel - in that case, we should tell the kernel about it so the
> watchdog framework can keep it alive until userspace opens
> /dev/watchdog0.
>

Separate note: The maximum timeout for this watchdog is 15 seconds.
Given that, it might be useful to set max_hw_heartbeat_ms instead of
max_timeout. Separate patch, though.

> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> ---
> drivers/watchdog/bcm2835_wdt.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/drivers/watchdog/bcm2835_wdt.c b/drivers/watchdog/bcm2835_wdt.c
> index 4dddd82..9a08334 100644
> --- a/drivers/watchdog/bcm2835_wdt.c
> +++ b/drivers/watchdog/bcm2835_wdt.c
> @@ -55,6 +55,15 @@ struct bcm2835_wdt {
> static unsigned int heartbeat;
> static bool nowayout = WATCHDOG_NOWAYOUT;
>
> +static bool bcm2835_wdt_is_running(struct bcm2835_wdt *wdt)
> +{
> + uint32_t cur;
> +
> + cur = readl(wdt->base + PM_RSTC);
> +
> + return !!(cur & PM_RSTC_WRCFG_FULL_RESET);
> +}
> +
> static int bcm2835_wdt_start(struct watchdog_device *wdog)
> {
> struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
> @@ -70,6 +79,7 @@ static int bcm2835_wdt_start(struct watchdog_device *wdog)
> PM_RSTC_WRCFG_FULL_RESET, wdt->base + PM_RSTC);
>
> spin_unlock_irqrestore(&wdt->lock, flags);
> + set_bit(WDOG_HW_RUNNING, &wdog->status);
>
You don't need to set this bit here unless the watchdog can not be stopped.

> return 0;
> }
> @@ -79,6 +89,7 @@ static int bcm2835_wdt_stop(struct watchdog_device *wdog)
> struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
>
> writel_relaxed(PM_PASSWORD | PM_RSTC_RESET, wdt->base + PM_RSTC);
> + clear_bit(WDOG_HW_RUNNING, &wdog->status);

... and since you clear the bit, it can be stopped. Both setting and resetting the bit
is therefore not necessary.

> return 0;
> }
>
> @@ -181,6 +192,17 @@ static int bcm2835_wdt_probe(struct platform_device *pdev)
> watchdog_init_timeout(&bcm2835_wdt_wdd, heartbeat, dev);
> watchdog_set_nowayout(&bcm2835_wdt_wdd, nowayout);
> bcm2835_wdt_wdd.parent = &pdev->dev;
> + if (bcm2835_wdt_is_running(wdt)) {
> + /*
> + * The currently active timeout value (set by the
> + * bootloader) may be different from the module
> + * heartbeat parameter or the value in device
> + * tree. But we just need to set WDOG_HW_RUNNING,
> + * because then the framework will "immediately" ping
> + * the device, updating the timeout.
> + */
> + set_bit(WDOG_HW_RUNNING, &bcm2835_wdt_wdd.status);
> + }
> err = watchdog_register_device(&bcm2835_wdt_wdd);
> if (err) {
> dev_err(dev, "Failed to register watchdog device");
>

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