linux-kernel - Re: [PATCH 1/5] pmdomain: core: Restore behaviour for disabling unused PM domains

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Message-ID: <CAMuHMdUFXioe36r9mzNchHw3DGyEiVA-=ajTp333jowEsrxMNw@mail.gmail.com>
Date: Thu, 11 Sep 2025 09:56:00 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>, 
	Saravana Kannan <saravanak@...gle.com>, linux-pm@...r.kernel.org, 
	Stephen Boyd <sboyd@...nel.org>, "Rafael J . Wysocki" <rafael@...nel.org>, Heiko Stuebner <heiko@...ech.de>, 
	Sebastian Reichel <sebastian.reichel@...labora.com>, Sebin Francis <sebin.francis@...com>, 
	Diederik de Haas <didi.debian@...ow.org>, Bjorn Andersson <andersson@...nel.org>, 
	Abel Vesa <abel.vesa@...aro.org>, Peng Fan <peng.fan@....nxp.com>, 
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, Johan Hovold <johan@...nel.org>, 
	Maulik Shah <maulik.shah@....qualcomm.com>, Michal Simek <michal.simek@....com>, 
	Konrad Dybcio <konradybcio@...nel.org>, Thierry Reding <thierry.reding@...il.com>, 
	Jonathan Hunter <jonathanh@...dia.com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] pmdomain: core: Restore behaviour for disabling
 unused PM domains

Hi Ulf,

On Tue, 9 Sept 2025 at 13:11, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> Recent changes to genpd prevents those PM domains being powered-on during
> initialization from being powered-off during the boot sequence. Based upon
> whether CONFIG_PM_CONFIG_PM_GENERIC_DOMAINS_OF is set of not, genpd relies
> on the sync_state mechanism or the genpd_power_off_unused() (which is a
> late_initcall_sync), to understand when it's okay to allow these PM domains
> to be powered-off.
>
> This new behaviour in genpd has lead to problems on different platforms.
> Let's therefore restore the behavior of genpd_power_off_unused().
> Moreover, let's introduce GENPD_FLAG_NO_STAY_ON, to allow genpd OF
> providers to opt-out from the new behaviour.
>
> Link: https://lore.kernel.org/all/20250701114733.636510-1-ulf.hansson@linaro.org/
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Link: https://lore.kernel.org/all/20250902-rk3576-lockup-regression-v1-1-c4a0c9daeb00@collabora.com/
> Reported-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> Fixes: 0e789b491ba0 ("pmdomain: core: Leave powered-on genpds on until sync_state")
> Fixes: 13a4b7fb6260 ("pmdomain: core: Leave powered-on genpds on until late_initcall_sync")
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>

> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -115,6 +115,12 @@ struct dev_pm_domain_list {
>   *                             genpd provider specific way, likely through a
>   *                             parent device node. This flag makes genpd to
>   *                             skip its internal support for this.
> + *
> + * GENPD_FLAG_NO_STAY_ON:      For genpd OF providers a powered-on PM domain at
> + *                             initialization is prevented from being
> + *                             powered-off until the ->sync_state() callback is
> + *                             invoked. This flag informs genpd to allow a
> + *                             power-off without waiting for ->sync_state().

This also restores power-down of pmdomains after a failed device
probe (due to a real issue, or just -EPROBE_DEFER), possibly
interfering with other devices that are part of the same pmdomain(s)
but haven't been probed yet. E.g. what if your serial console is
part of the same pmdomain?  Probably the pmdomain(s) should not
be powered down immediately, but only later, when either sync state
or genpd_power_off_unused() kicks in.

But this is a pre-existing issue, so not a blocked for this patch.

>   */
>  #define GENPD_FLAG_PM_CLK       (1U << 0)
>  #define GENPD_FLAG_IRQ_SAFE     (1U << 1)

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