linux-kernel - Re: [PATCH 4/5] pmdomain: renesas: rcar-gen4-sysc: Don't keep unused PM domains powered-on

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Message-ID: <CAMuHMdV5JoLtWXMyKuAUCZJ9eHNmwq+9tgxoZp_tra5EsR0MNw@mail.gmail.com>
Date: Thu, 11 Sep 2025 09:57:34 +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 4/5] pmdomain: renesas: rcar-gen4-sysc: Don't keep unused
 PM domains powered-on

On Tue, 9 Sept 2025 at 13:11, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> The recent changes to genpd makes a genpd OF provider that is powered-on at
> initialization to stay powered-on, until the ->sync_state() callback is
> invoked for it.
>
> This may not happen at all, if we wait for a consumer device to be probed,
> leading to wasting energy. There are ways to enforce the ->sync_state()
> callback to be invoked, through sysfs or via the probe-defer-timeout, but
> none of them in its current form are a good fit for rcar-gen4-sysc PM
> domains.
>
> Let's therefore opt-out from this behaviour of genpd for now, by using the
> GENPD_FLAG_NO_STAY_ON.
>
> Link: https://lore.kernel.org/all/20250701114733.636510-1-ulf.hansson@linaro.org/
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> 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>

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>
on R-Car V4M (gray hawk single).

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