RE: [PATCH v5 12/26] watchdog: renesas_wdt: Add R-Car Gen2 support

[Fabrizio Castro]

Hi Geert,

thank you for your feedback!

> Subject: Re: [PATCH v5 12/26] watchdog: renesas_wdt: Add R-Car Gen2 support
>
> Hi Fabrizio,
>
> On Mon, Feb 12, 2018 at 6:44 PM, Fabrizio Castro
> <fabrizio.cas...@bp.renesas.com> wrote:
> > Due to commits:
> > * "ARM: shmobile: Add watchdog support",
> > * "ARM: shmobile: rcar-gen2: Add watchdog support", and
> > * "soc: renesas: rcar-rst: Enable watchdog as reset trigger for Gen2",
> > we now have everything we needed for the watchdog to work on Gen2 and
> > RZ/G1.
> >
> > This commit adds "renesas,rcar-gen2-wdt" as compatible string for R-Car
> > Gen2 and RZ/G1, and since on those platforms the rwdt clock needs to be
> > always ON, when suspending to RAM we need to explicitly disable the
> > counting by clearing TME from RWTCSRA.
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.cas...@bp.renesas.com>
> > Signed-off-by: Ramesh Shanmugasundaram 
> > <ramesh.shanmugasunda...@bp.renesas.com>
>
> Thanks for your patch!
>
> I verified this works on R-Car Gen2, so
> Reviewed-and-Tested-by: Geert Uytterhoeven <geert+rene...@glider.be>
>
> Still, more comments below...
>
> > --- a/drivers/watchdog/renesas_wdt.c
> > +++ b/drivers/watchdog/renesas_wdt.c
> > @@ -203,13 +203,29 @@ 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.
> > - */
> > +static int __maybe_unused rwdt_suspend(struct device *dev)
> > +{
> > +   struct rwdt_priv *priv = dev_get_drvdata(dev);
> > +
> > +   if (watchdog_active(>wdev))
> > +   rwdt_write(priv, priv->cks, RWTCSRA);
> > +   return 0;
> > +}
> > +
> > +static int __maybe_unused rwdt_resume(struct device *dev)
> > +{
> > +   struct rwdt_priv *priv = dev_get_drvdata(dev);
> > +
> > +   if (watchdog_active(>wdev))
> > +   rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);
>
> Writing to this register is not sufficient on R-Car Gen3, where PSCI
> suspend powers down the whole SoC.  Hence all WDT register content is lost,
> causing the watchdog timeout never to trigger.
> Note that this issue is pre-existing, and not caused by your patch.
>
> This can be fixed by replacing the RWTCSRA register writes in the
> suspend/resume handlers by calls to rwdt_stop() resp. rwdt_start(), like is
> done in the BSP in commit e406980763f18f38 ("watchdog: renesas-wdt: Support
> the suspend/resume"). Note that this would cause a small change in behavior
> on R-Car Gen2, where the timeout would be reset on resume, instead of
> continuing where stopped before. I don't think that hurts, though.

I see, well I believe we can make both of us happy by addressing Gen3
problems and preserving the original behaviour  from Gen2.

I am going to send a new series to address this shortly.

>
> Since I was always a bit uncomfortable with this patch doing two things at
> once (1. suspend/resume, 2. "renesas,rcar-gen2-wdt" matching), I think it
> would be better to take the patch from the BSP first, and add support for
> "renesas,rcar-gen2-wdt" in a subsequent patch.

I agree, I'll split the patch and submit suspend/resume first, Gen2 
compatibility
next.

Thanks,
Fab

>
> Does the above make sense?
> Do you agree?
>
> Thanks!
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- 
> ge...@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like 
> that.
> -- Linus Torvalds



Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, 
Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered 
No. 04586709.

Re: [PATCH v5 12/26] watchdog: renesas_wdt: Add R-Car Gen2 support

[Geert Uytterhoeven]

Hi Fabrizio,

On Mon, Feb 12, 2018 at 6:44 PM, Fabrizio Castro
 wrote:
> Due to commits:
> * "ARM: shmobile: Add watchdog support",
> * "ARM: shmobile: rcar-gen2: Add watchdog support", and
> * "soc: renesas: rcar-rst: Enable watchdog as reset trigger for Gen2",
> we now have everything we needed for the watchdog to work on Gen2 and
> RZ/G1.
>
> This commit adds "renesas,rcar-gen2-wdt" as compatible string for R-Car
> Gen2 and RZ/G1, and since on those platforms the rwdt clock needs to be
> always ON, when suspending to RAM we need to explicitly disable the
> counting by clearing TME from RWTCSRA.
>
> Signed-off-by: Fabrizio Castro 
> Signed-off-by: Ramesh Shanmugasundaram 
> 

Thanks for your patch!

I verified this works on R-Car Gen2, so
Reviewed-and-Tested-by: Geert Uytterhoeven 

Still, more comments below...

> --- a/drivers/watchdog/renesas_wdt.c
> +++ b/drivers/watchdog/renesas_wdt.c
> @@ -203,13 +203,29 @@ 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.
> - */
> +static int __maybe_unused rwdt_suspend(struct device *dev)
> +{
> +   struct rwdt_priv *priv = dev_get_drvdata(dev);
> +
> +   if (watchdog_active(>wdev))
> +   rwdt_write(priv, priv->cks, RWTCSRA);
> +   return 0;
> +}
> +
> +static int __maybe_unused rwdt_resume(struct device *dev)
> +{
> +   struct rwdt_priv *priv = dev_get_drvdata(dev);
> +
> +   if (watchdog_active(>wdev))
> +   rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);

Writing to this register is not sufficient on R-Car Gen3, where PSCI
suspend powers down the whole SoC.  Hence all WDT register content is lost,
causing the watchdog timeout never to trigger.
Note that this issue is pre-existing, and not caused by your patch.

This can be fixed by replacing the RWTCSRA register writes in the
suspend/resume handlers by calls to rwdt_stop() resp. rwdt_start(), like is
done in the BSP in commit e406980763f18f38 ("watchdog: renesas-wdt: Support
the suspend/resume"). Note that this would cause a small change in behavior
on R-Car Gen2, where the timeout would be reset on resume, instead of
continuing where stopped before. I don't think that hurts, though.

Since I was always a bit uncomfortable with this patch doing two things at
once (1. suspend/resume, 2. "renesas,rcar-gen2-wdt" matching), I think it
would be better to take the patch from the BSP first, and add support for
"renesas,rcar-gen2-wdt" in a subsequent patch.

Does the above make sense?
Do you agree?

Thanks!

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Re: [PATCH v5 12/26] watchdog: renesas_wdt: Add R-Car Gen2 support

[Wolfram Sang]

On Mon, Feb 12, 2018 at 05:44:21PM +, Fabrizio Castro wrote:
> Due to commits:
> * "ARM: shmobile: Add watchdog support",
> * "ARM: shmobile: rcar-gen2: Add watchdog support", and
> * "soc: renesas: rcar-rst: Enable watchdog as reset trigger for Gen2",
> we now have everything we needed for the watchdog to work on Gen2 and
> RZ/G1.
> 
> This commit adds "renesas,rcar-gen2-wdt" as compatible string for R-Car
> Gen2 and RZ/G1, and since on those platforms the rwdt clock needs to be
> always ON, when suspending to RAM we need to explicitly disable the
> counting by clearing TME from RWTCSRA.
> 
> Signed-off-by: Fabrizio Castro 
> Signed-off-by: Ramesh Shanmugasundaram 
> 
> ---
> v4->v5:
> * various improvements suggested by Wolfram
> 

Reviewed-by: Wolfram Sang 



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Re: [PATCH v5 12/26] watchdog: renesas_wdt: Add R-Car Gen2 support

[Guenter Roeck]

On Mon, Feb 12, 2018 at 05:44:21PM +, Fabrizio Castro wrote:
> Due to commits:
> * "ARM: shmobile: Add watchdog support",
> * "ARM: shmobile: rcar-gen2: Add watchdog support", and
> * "soc: renesas: rcar-rst: Enable watchdog as reset trigger for Gen2",
> we now have everything we needed for the watchdog to work on Gen2 and
> RZ/G1.
> 
> This commit adds "renesas,rcar-gen2-wdt" as compatible string for R-Car
> Gen2 and RZ/G1, and since on those platforms the rwdt clock needs to be
> always ON, when suspending to RAM we need to explicitly disable the
> counting by clearing TME from RWTCSRA.
> 
> Signed-off-by: Fabrizio Castro 
> Signed-off-by: Ramesh Shanmugasundaram 
> 

Reviewed-by: Guenter Roeck 

> ---
> v4->v5:
> * various improvements suggested by Wolfram
> 
>  drivers/watchdog/renesas_wdt.c | 27 ++-
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> index 831ef83..e972b7b 100644
> --- a/drivers/watchdog/renesas_wdt.c
> +++ b/drivers/watchdog/renesas_wdt.c
> @@ -203,13 +203,29 @@ 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.
> - */
> +static int __maybe_unused rwdt_suspend(struct device *dev)
> +{
> + struct rwdt_priv *priv = dev_get_drvdata(dev);
> +
> + if (watchdog_active(>wdev))
> + rwdt_write(priv, priv->cks, RWTCSRA);
> + return 0;
> +}
> +
> +static int __maybe_unused rwdt_resume(struct device *dev)
> +{
> + struct rwdt_priv *priv = dev_get_drvdata(dev);
> +
> + if (watchdog_active(>wdev))
> + rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);
> + return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(rwdt_pm_ops, rwdt_suspend, rwdt_resume);
> +
>  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 +234,7 @@ static struct platform_driver rwdt_driver = {
>   .driver = {
>   .name = "renesas_wdt",
>   .of_match_table = rwdt_ids,
> + .pm = _pm_ops,
>   },
>   .probe = rwdt_probe,
>   .remove = rwdt_remove,
> -- 
> 2.7.4
> 

[PATCH v5 12/26] watchdog: renesas_wdt: Add R-Car Gen2 support

[Fabrizio Castro]

Due to commits:
* "ARM: shmobile: Add watchdog support",
* "ARM: shmobile: rcar-gen2: Add watchdog support", and
* "soc: renesas: rcar-rst: Enable watchdog as reset trigger for Gen2",
we now have everything we needed for the watchdog to work on Gen2 and
RZ/G1.

This commit adds "renesas,rcar-gen2-wdt" as compatible string for R-Car
Gen2 and RZ/G1, and since on those platforms the rwdt clock needs to be
always ON, when suspending to RAM we need to explicitly disable the
counting by clearing TME from RWTCSRA.

Signed-off-by: Fabrizio Castro 
Signed-off-by: Ramesh Shanmugasundaram 
---
v4->v5:
* various improvements suggested by Wolfram

 drivers/watchdog/renesas_wdt.c | 27 ++-
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
index 831ef83..e972b7b 100644
--- a/drivers/watchdog/renesas_wdt.c
+++ b/drivers/watchdog/renesas_wdt.c
@@ -203,13 +203,29 @@ 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.
- */
+static int __maybe_unused rwdt_suspend(struct device *dev)
+{
+   struct rwdt_priv *priv = dev_get_drvdata(dev);
+
+   if (watchdog_active(>wdev))
+   rwdt_write(priv, priv->cks, RWTCSRA);
+   return 0;
+}
+
+static int __maybe_unused rwdt_resume(struct device *dev)
+{
+   struct rwdt_priv *priv = dev_get_drvdata(dev);
+
+   if (watchdog_active(>wdev))
+   rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);
+   return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(rwdt_pm_ops, rwdt_suspend, rwdt_resume);
+
 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 +234,7 @@ static struct platform_driver rwdt_driver = {
.driver = {
.name = "renesas_wdt",
.of_match_table = rwdt_ids,
+   .pm = _pm_ops,
},
.probe = rwdt_probe,
.remove = rwdt_remove,
-- 
2.7.4