linux-kernel - Re: [PATCH v3 4/4] watchdog: rzg2l_wdt: Power on the watchdog domain in the restart handler

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Message-ID: <CAMuHMdVU2CRfN0Qpk0QH1qJXV9ohGfY_maybWYsjEi7A8ggpBw@mail.gmail.com>
Date: Mon, 7 Oct 2024 16:34:43 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Claudiu <claudiu.beznea@...on.dev>
Cc: mturquette@...libre.com, sboyd@...nel.org, wim@...ux-watchdog.org, 
	linux@...ck-us.net, ulf.hansson@...aro.org, linux-renesas-soc@...r.kernel.org, 
	linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-watchdog@...r.kernel.org, linux-pm@...r.kernel.org, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v3 4/4] watchdog: rzg2l_wdt: Power on the watchdog domain
 in the restart handler

On Mon, Sep 2, 2024 at 3:24 PM Claudiu <claudiu.beznea@...on.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> On RZ/G3S the watchdog can be part of a software-controlled PM domain. In
> this case, the watchdog device need to be powered on in
> struct watchdog_ops::restart API. This can be done though
> pm_runtime_resume_and_get() API if the watchdog PM domain and watchdog
> device are marked as IRQ safe. We mark the watchdog PM domain as IRQ safe
> with GENPD_FLAG_IRQ_SAFE when the watchdog PM domain is registered and the
> watchdog device though pm_runtime_irq_safe().
>
> Before commit e4cf89596c1f ("watchdog: rzg2l_wdt: Fix 'BUG: Invalid wait
> context'") pm_runtime_get_sync() was used in watchdog restart handler
> (which is similar to pm_runtime_resume_and_get() except the later one
> handles the runtime resume errors).
>
> Commit e4cf89596c1f ("watchdog: rzg2l_wdt: Fix 'BUG: Invalid wait
> context'") dropped the pm_runtime_get_sync() and replaced it with
> clk_prepare_enable() to avoid invalid wait context due to genpd_lock()
> in genpd_runtime_resume() being called from atomic context. But
> clk_prepare_enable() doesn't fit for this either (as reported by
> Ulf Hansson) as clk_prepare() can also sleep (it just not throw invalid
> wait context warning as it is not written for this).
>
> Because the watchdog device is marked now as IRQ safe (though this patch)
> the irq_safe_dev_in_sleep_domain() call from genpd_runtime_resume() returns
> 1 for devices not registering an IRQ safe PM domain for watchdog (as the
> watchdog device is IRQ safe, PM domain is not and watchdog PM domain is
> always-on), this being the case for RZ/G3S with old device trees and
> the rest of the SoCs that use this driver, we can now drop also the
> clk_prepare_enable() calls in restart handler and rely on
> pm_runtime_resume_and_get().
>
> Thus, drop clk_prepare_enable() and use pm_runtime_resume_and_get() in
> watchdog restart handler.
>
> Acked-by: Guenter Roeck <linux@...ck-us.net>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> ---
>
> Changes in v4:
> - collected Ulf's tag

LGTM, so
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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