Hi, Ulf,
Sorry for the late reply, I was off last week.
On 13.08.2024 16:56, Ulf Hansson wrote:
> On Wed, 19 Jun 2024 at 14:09, Claudiu <claudiu.beznea@xxxxxxxxx> wrote:
>>
>> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>>
>> The rzg2l_wdt_restart() is called in atomic context. Calling
>> pm_runtime_{get_sync, resume_and_get}() or any other runtime PM resume
>> APIs is not an option as it may lead to issues as described in commit
>> e4cf89596c1f ("watchdog: rzg2l_wdt: Fix 'BUG: Invalid wait context'")
>> that removed the pm_runtime_get_sync() and enabled directly the clocks.
>>
>> Starting with RZ/G3S the watchdog could be part of its own
>> software-controlled power domain. In case the watchdog is not used the
>> power domain is off and accessing watchdog registers leads to aborts.
>>
>> To solve this, the patch powers on the power domain using
>> dev_pm_genpd_resume_restart_dev() API after enabling its clock. This is
>> not sleeping or taking any other locks as the watchdog power domain is not
>> registered with GENPD_FLAG_IRQ_SAFE flags.
>
> Would it be a problem to register the corresponding genpd using the
> GENPD_FLAG_IRQ_SAFE?
Should be no problem, AFIK.
>
> Assuming it wouldn't, it looks like we should be able to make the
> watchdog device irq-safe too, by calling pm_runtime_irq_safe() during
> ->probe().
>
> In that case it should be okay to call pm_runtime_get_sync() in atomic
> context, right?
Right! I registered the watchdog domain with GENPD_FLAG_IRQ_SAFE as well as
it's parent domain (the always-on domain) and all looks good. However I
need to run further testing to be sure nothing is broken.
Thank you,
Claudiu Beznea
>
> Kind regards
> Uffe
>
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>> ---
>> drivers/watchdog/rzg2l_wdt.c | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/drivers/watchdog/rzg2l_wdt.c b/drivers/watchdog/rzg2l_wdt.c
>> index 6e3d7512f38c..bbdbbaa7b82b 100644
>> --- a/drivers/watchdog/rzg2l_wdt.c
>> +++ b/drivers/watchdog/rzg2l_wdt.c
>> @@ -12,6 +12,7 @@
>> #include <linux/module.h>
>> #include <linux/of.h>
>> #include <linux/platform_device.h>
>> +#include <linux/pm_domain.h>
>> #include <linux/pm_runtime.h>
>> #include <linux/reset.h>
>> #include <linux/units.h>
>> @@ -169,6 +170,17 @@ static int rzg2l_wdt_restart(struct watchdog_device *wdev,
>> clk_enable(priv->pclk);
>> clk_enable(priv->osc_clk);
>>
>> + /*
>> + * The device may be part of a power domain that is currently
>> + * powered off. We need to power it on before accessing registers.
>> + * We don't undo the dev_pm_genpd_resume_restart_dev() as the device
>> + * need to be on for the reboot to happen. Also, as we are in atomic
>> + * context here, there is no need to increment PM runtime usage counter
>> + * (to make sure pm_runtime_active() doesn't return wrong code).
>> + */
>> + if (!pm_runtime_active(wdev->parent))
>> + dev_pm_genpd_resume_restart_dev(wdev->parent);
>> +
>> if (priv->devtype == WDT_RZG2L) {
>> ret = reset_control_deassert(priv->rstc);
>> if (ret)
>> --
>> 2.39.2
>>
