On Mon, Apr 15, 2019 at 12:52:01PM +0200, Wolfram Sang wrote:
> Support an already running watchdog by checking its enable bit and set
> up the status accordingly before registering the device.
>
> Signed-off-by: Wolfram Sang <wsa+rene...@sang-engineering.com>
> ---
>
> This patch was tested using a Renesas Salvator XS board (R-Car M3N). It works.
> However, there is a small window where the watchdog clock is disabled, namely
> after the MSSR clock driver initializes it until RuntimePM of the watchdog
> driver takes over. If the system hangs in this window, bad luck. So, I'd think
> it makes sense to have this clock either always-on or to keep the state which
> came from the firmware. Geert, what do you think?
>
> drivers/watchdog/renesas_wdt.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> index 565dbc1ec638..37d757288b22 100644
> --- a/drivers/watchdog/renesas_wdt.c
> +++ b/drivers/watchdog/renesas_wdt.c
> @@ -179,6 +179,7 @@ static int rwdt_probe(struct platform_device *pdev)
> struct clk *clk;
> unsigned long clks_per_sec;
> int ret, i;
> + u8 csra;
>
> if (rwdt_blacklisted(&pdev->dev))
> return -ENODEV;
> @@ -198,8 +199,8 @@ static int rwdt_probe(struct platform_device *pdev)
> pm_runtime_enable(&pdev->dev);
> pm_runtime_get_sync(&pdev->dev);
> priv->clk_rate = clk_get_rate(clk);
> - priv->wdev.bootstatus = (readb_relaxed(priv->base + RWTCSRA) &
> - RWTCSRA_WOVF) ? WDIOF_CARDRESET : 0;
> + csra = readb_relaxed(priv->base + RWTCSRA);
> + priv->wdev.bootstatus = csra & RWTCSRA_WOVF ? WDIOF_CARDRESET : 0;
> pm_runtime_put(&pdev->dev);
>
> if (!priv->clk_rate) {
> @@ -237,6 +238,16 @@ static int rwdt_probe(struct platform_device *pdev)
> /* This overrides the default timeout only if DT configuration was
> found */
> watchdog_init_timeout(&priv->wdev, 0, &pdev->dev);
>
> + if (csra & RWTCSRA_TME) {
> + /* Ensure properly initialized dividers */
> + rwdt_start(&priv->wdev);
> + set_bit(WDOG_HW_RUNNING, &priv->wdev.status);
> + //FIXME: We are missing pm_runtime_put in some code paths to
> + // to balance PM calls. We first need to decide if we maybe
> + // should have the RWDT clock always-on or if using RPM for
> + // clock management is OK.
Maybe I am missing something, but ..
Is handover even possible if the clock is controlled by clock management ?
Seems to me the clock would then be turned off through pm, which effectively
turns off the watchdog. So it will be off between clock/pm initialization
and the above code, meaning wdt handover from the boot loader is for all
practical purposes useless if the kernel gets stuck in between.
Thanks,
Guenter
> + }
> +
> ret = watchdog_register_device(&priv->wdev);
> if (ret < 0)
> goto out_pm_disable;
> --
> 2.11.0
>
