On Wed, Feb 21, 2018 at 04:43:04PM +0100, Geert Uytterhoeven wrote:
> 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).
>
> Prevent using the watchdog in impacted cases 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: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---
> To be folded into Fabrizio Castro's "watchdog: renesas_wdt: Add R-Car
> Gen2 support".
>
> Note that I cannot use IS_ENABLED(CONFIG_SMP), as setup_max_cpus does
> not exist for CONFIG_SMP=n.
Thanks, I was going to ask about that.
Reviewed-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> Any reports on R-Car M2-W ES2.0 and V2H ES2.0+ are welcomed!
>
> As the failure is due to an integration issue, and the watchdog itself
> is working fine, an alternative solution would be to move the check to
> the code that installs the reset trigger ("soc: renesas: rcar-rst:
> Enable watchdog as reset trigger for Gen2").
> However, doing so would mean that:
> 1. The user could enable and seemingly use the watchdog, but watchdog
> timeout would not restart the system,
> 2. The same check should be done before installing the new reset
> vector ("ARM: shmobile: rcar-gen2: Add watchdog support"), too,
> else onlining CPU0 would fail once the watchdog has timed out.
> ---
> drivers/watchdog/renesas_wdt.c | 43 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
>
> diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> index 0f88614797c36022..4c8e8d2600a922a5 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
> @@ -131,6 +133,44 @@ static const struct watchdog_ops rwdt_ops = {
> .restart = rwdt_restart,
> };
>
> +#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;
> @@ -139,6 +179,9 @@ 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;
> --
> 2.7.4
>
