linux-kernel - Re: [PATCH 2/3] clk: samsung: fix sysreg save/restore when PM is enabled for CMU

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Message-ID: <CADrjBPpiMxNsHMnV8StHvU7waW3QE7jtAPK3Gyq-j0mVRQrgnw@mail.gmail.com>
Date: Mon, 12 Jan 2026 14:29:56 +0000
From: Peter Griffin <peter.griffin@...aro.org>
To: André Draszik <andre.draszik@...aro.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Sylwester Nawrocki <s.nawrocki@...sung.com>, 
	Chanwoo Choi <cw00.choi@...sung.com>, Alim Akhtar <alim.akhtar@...sung.com>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Tudor Ambarus <tudor.ambarus@...aro.org>, Will McVicker <willmcvicker@...gle.com>, 
	Juan Yescas <jyescas@...gle.com>, linux-samsung-soc@...r.kernel.org, 
	linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] clk: samsung: fix sysreg save/restore when PM is
 enabled for CMU

On Fri, 9 Jan 2026 at 17:27, André Draszik <andre.draszik@...aro.org> wrote:
>
> Currently, sysreg registers of a CMU that has PM and automatic clock
> gating enabled are not saved / restored during runtime PM (RPM) or
> s2idle. During normal suspend, they are accessed too late, after the
> CMU (and potentially power domain) have been shut down, causing an
> SError.
>
> The reason is that these registers are registered to be saved/restored
> via a syscore suspend handler which doesn't run during RPM or s2idle.
> During normal suspend, this handler runs after the CMU has been shut
> down. This registration happens as part of
> samsung_clk_extended_sleep_init() via samsung_en_dyn_root_clk_gating().
>
> When PM is enabled for a CMU, registers must be saved/restored via
> exynos_arm64_cmu_suspend() / exynos_arm64_cmu_resume() respectively
> instead. These use their own data structures and are unrelated to
> anything that samsung_clk_extended_sleep_init() does. Calling it
> unconditionally from samsung_en_dyn_root_clk_gating() therefore isn't
> useful.
>
> Update the code to prepare sysreg save / restore in a similar way to
> how it handles other clock registers in the PM case already.
> exynos_arm64_cmu_suspend() / exynos_arm64_cmu_resume() already handle
> sysreg save/restore, just the setup was incorrect.
>
> Fixes: 298fac4f4b96 ("clk: samsung: Implement automatic clock gating mode for CMUs")
> Signed-off-by: André Draszik <andre.draszik@...aro.org>
> ---

Reviewed-by: Peter Griffin <peter.griffin@...aro.org>