[RFC v3 11/25] watchdog: renesas_wdt: Add R-Car Gen2 support

[Fabrizio Castro]

Hello Guenter,

thank you for your feedback.

> Subject: Re: [RFC v3 11/25] watchdog: renesas_wdt: Add R-Car Gen2 support
>
> On Tue, Jan 30, 2018 at 08:22:44PM +0000, Fabrizio Castro wrote:
> > On R-Car Gen2 and RZ/G1 the rwdt clock needs to be always ON, therefore
> > when suspending to RAM we need to explicitly disable the counting by
> > clearing TME from RWTCSRA.
> > Also, on some systems RWDT is the only piece of HW that allows the SoC
> > to be restarted, therefore this patch implements the restart callback.
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.castro at bp.renesas.com>
> > Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram at bp.renesas.com>
> > ---
> > Wolfram, was the restart callback implementation missing for a reason?
> > Is its implementation going to break any Gen3 platform?
> >
>
> The changes clearly are way more than claimed in the subject. Adding
> restart handler and PM support may be prerequisites for Gen2, but the
> changes apply to Gen3 as well. What happened to "one patch per logical
> change" ?

The PM implementation should be ok for Gen3 too, without this patch series the kernel
would disable the rwdt clock when suspending to RAM, this would "pause" the counting.
This patch series declares the rwdt clock as critical for Gen2 and RZ/G1, which means we
need to explicitly disable the counting to keep the same behaviour in place.
With respect to the restart callback implementation, that may well have consequences on
Gen3, hopefully Wolfram will give us a feedback on this.
In particular I would like to know if we should be installing the restart callback only when
we use "renesas,rcar-gen2-wdt" as compatible string, or it's ok to make it available for
Gen3 as well.
The only way to reboot iWave's boards iwg20d and iwg22d is to use the internal watchdog,
that's why the restart implementation was merged into this patch.
I can split this patch in two, one for PM support and one for restart support for the next
version, what do you think about this?

>
> > v1->v3:
> > * unified Gen2 and Gen3 drivers.
> >
> >  drivers/watchdog/renesas_wdt.c | 61 ++++++++++++++++++++++++++++++++++++++----
> >  1 file changed, 56 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> > index 831ef83..eedb016 100644
> > --- a/drivers/watchdog/renesas_wdt.c
> > +++ b/drivers/watchdog/renesas_wdt.c
> > @@ -107,6 +107,24 @@ static unsigned int rwdt_get_timeleft(struct watchdog_device *wdev)
> >  return DIV_BY_CLKS_PER_SEC(priv, 65536 - val);
> >  }
> >
> > +static int rwdt_restart(struct watchdog_device *wdev, unsigned long action,
> > +void *data)
> > +{
> > +struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
> > +
> > +pm_runtime_get_sync(wdev->parent);
> > +
> > +rwdt_write(priv, 0x00, RWTCSRB);
> > +rwdt_write(priv, 0x00, RWTCSRA);
> > +rwdt_write(priv, 0xffff, RWTCNT);
> > +
> > +while (readb_relaxed(priv->base + RWTCSRA) & RWTCSRA_WRFLG)
> > +cpu_relax();
> > +
> > +rwdt_write(priv, 0x80, RWTCSRA);
> > +return 0;
> > +}
> > +
> >  static const struct watchdog_info rwdt_ident = {
> >  .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
> >  .identity = "Renesas WDT Watchdog",
> > @@ -118,6 +136,7 @@ static const struct watchdog_ops rwdt_ops = {
> >  .stop = rwdt_stop,
> >  .ping = rwdt_init_timeout,
> >  .get_timeleft = rwdt_get_timeleft,
> > +.restart = rwdt_restart,
> >  };
> >
> >  static int rwdt_probe(struct platform_device *pdev)
> > @@ -203,13 +222,42 @@ static int rwdt_remove(struct platform_device *pdev)
> >  return 0;
> >  }
> >
> > -/*
> > - * This driver does also fit for R-Car Gen2 (r8a779[0-4]) WDT. However, for SMP
> > - * to work there, one also needs a RESET (RST) driver which does not exist yet
> > - * due to HW issues. This needs to be solved before adding compatibles here.
> > - */
>
> Have those issues been resolved ?

This patch series addresses precisely those issues. The first implementation
used a flag that the watchdog driver needed to explicitly set to make everything
work as expected. This new version uses a different concept that doesn't require
such an hack, and that's why the proposal now is to merge Gen2 and Gen3 drivers.

Thanks,
Fab

>
> > +#ifdef CONFIG_PM
> > +static int rwdt_suspend(struct device *dev)
> > +{
> > +struct platform_device *pdev;
> > +struct rwdt_priv *priv;
> > +
> > +pdev = to_platform_device(dev);
> > +priv = platform_get_drvdata(pdev);
> > +if (watchdog_active(&priv->wdev)) {
> > +rwdt_write(priv, priv->cks, RWTCSRA);
> > +}
> > +return 0;
> > +}
> > +
> > +static int rwdt_resume(struct device *dev)
> > +{
> > +struct platform_device *pdev;
> > +struct rwdt_priv *priv;
> > +
> > +pdev = to_platform_device(dev);
> > +priv = platform_get_drvdata(pdev);
> > +if (watchdog_active(&priv->wdev)) {
> > +rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);
> > +}
> > +return 0;
> > +}
> > +
> > +static const struct dev_pm_ops rwdt_pm = {
> > +.suspend = rwdt_suspend,
> > +.resume = rwdt_resume,
> > +};
> > +#endif
> > +
> >  static const struct of_device_id rwdt_ids[] = {
> >  { .compatible = "renesas,rcar-gen3-wdt", },
> > +{ .compatible = "renesas,rcar-gen2-wdt", },
> >  { /* sentinel */ }
> >  };
> >  MODULE_DEVICE_TABLE(of, rwdt_ids);
> > @@ -218,6 +266,9 @@ static struct platform_driver rwdt_driver = {
> >  .driver = {
> >  .name = "renesas_wdt",
> >  .of_match_table = rwdt_ids,
> > +#ifdef CONFIG_PM
> > +.pm = &rwdt_pm,
> > +#endif
> >  },
> >  .probe = rwdt_probe,
> >  .remove = rwdt_remove,
> > --
> > 2.7.4
> >



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