Re: [PATCH v8 2/3] watchdog: renesas_wdt: Add R-Car Gen2 support

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

On Mon, Mar 05, 2018 at 03:30:25PM +0000, 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.
> 
> However, on early revisions of some R-Car Gen2 SoCs, and depending on SMP
> configuration, the system may fail to restart on watchdog time-out, and
> lock up instead.
> 
> Specifically:
>   - On R-Car H2 ES1.0 and M2-W ES1.0, watchdog restart fails unless
>     only the first CPU core is in use (using e.g. the "maxcpus=1" kernel
>     commandline option).
>   - On R-Car V2H ES1.1, watchdog restart fails unless SMP is disabled
>     completely (using CONFIG_SMP=n during build configuration, or using
>     the "nosmp" or "maxcpus=0" kernel commandline options).
> 
> This commit adds "renesas,rcar-gen2-wdt" as compatible string for R-Car
> Gen2 and RZ/G1, but also prevents the system from using the watchdog
> driver in cases where the system would fail to restart by blacklisting
> the affected SoCs, using the minimum known working revisions (ES2.0 on R-Car
> H2, and ES3.0 on M2-W), and taking the actual SMP software configuration
> into account.
> 
> Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
> [Geert: blacklisting logic]
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> v7->v8:
> * folded patch "watchdog: renesas_wdt: Blacklist early R-Car Gen2 SoCs" from
>   Geert into this patch.
> 
> Since Simon only reviewed Geert's patch, and Wolfram and Guenter only reviewed
> earlier versions of this patch, I am not including their "Reviewed-by" as they
> may disagree with the final result.
> 

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> Thanks,
> Fab
> 
>  drivers/watchdog/renesas_wdt.c | 49 +++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 44 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> index 024d54e..0dede5b 100644
> --- a/drivers/watchdog/renesas_wdt.c
> +++ b/drivers/watchdog/renesas_wdt.c
> @@ -16,6 +16,8 @@
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/smp.h>
> +#include <linux/sys_soc.h>
>  #include <linux/watchdog.h>
>  
>  #define RWTCNT		0
> @@ -121,6 +123,44 @@ static const struct watchdog_ops rwdt_ops = {
>  	.get_timeleft = rwdt_get_timeleft,
>  };
>  
> +#if defined(CONFIG_ARCH_RCAR_GEN2) && defined(CONFIG_SMP)
> +/*
> + * Watchdog-reset integration is broken on early revisions of R-Car Gen2 SoCs
> + */
> +static const struct soc_device_attribute rwdt_quirks_match[] = {
> +	{
> +		.soc_id = "r8a7790",
> +		.revision = "ES1.*",
> +		.data = (void *)1,	/* needs single CPU */
> +	}, {
> +		.soc_id = "r8a7791",
> +		.revision = "ES[12].*",
> +		.data = (void *)1,	/* needs single CPU */
> +	}, {
> +		.soc_id = "r8a7792",
> +		.revision = "*",
> +		.data = (void *)0,	/* needs SMP disabled */
> +	},
> +	{ /* sentinel */ }
> +};
> +
> +static bool rwdt_blacklisted(struct device *dev)
> +{
> +	const struct soc_device_attribute *attr;
> +
> +	attr = soc_device_match(rwdt_quirks_match);
> +	if (attr && setup_max_cpus > (uintptr_t)attr->data) {
> +		dev_info(dev, "Watchdog blacklisted on %s %s\n", attr->soc_id,
> +			 attr->revision);
> +		return true;
> +	}
> +
> +	return false;
> +}
> +#else /* !CONFIG_ARCH_RCAR_GEN2 || !CONFIG_SMP */
> +static inline bool rwdt_blacklisted(struct device *dev) { return false; }
> +#endif /* !CONFIG_ARCH_RCAR_GEN2 || !CONFIG_SMP */
> +
>  static int rwdt_probe(struct platform_device *pdev)
>  {
>  	struct rwdt_priv *priv;
> @@ -129,6 +169,9 @@ static int rwdt_probe(struct platform_device *pdev)
>  	unsigned long clks_per_sec;
>  	int ret, i;
>  
> +	if (rwdt_blacklisted(&pdev->dev))
> +		return -ENODEV;
> +
>  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
>  	if (!priv)
>  		return -ENOMEM;
> @@ -228,12 +271,8 @@ static int __maybe_unused rwdt_resume(struct device *dev)
>  
>  static SIMPLE_DEV_PM_OPS(rwdt_pm_ops, rwdt_suspend, rwdt_resume);
>  
> -/*
> - * 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 const struct of_device_id rwdt_ids[] = {
> +	{ .compatible = "renesas,rcar-gen2-wdt", },
>  	{ .compatible = "renesas,rcar-gen3-wdt", },
>  	{ /* sentinel */ }
>  };
> -- 
> 2.7.4
> 
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