linux-kernel - Re: [PATCH] Revert "clk: qcom: cpu-8996: simplify the cpu_clk_notifier

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Message-ID: <8d769fb3-cd2a-492c-8aa3-064ebbc5eee4@oss.qualcomm.com>
Date: Wed, 3 Dec 2025 11:52:17 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Christopher Obbard <christopher.obbard@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd
 <sboyd@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Subject: Re: [PATCH] Revert "clk: qcom: cpu-8996: simplify the
 cpu_clk_notifier_cb"

On 12/2/25 10:24 PM, Christopher Obbard wrote:
> This reverts commit b3b274bc9d3d7307308aeaf75f70731765ac999a.
> 
> On the DragonBoard 820c (which uses APQ8096/MSM8996) this change causes
> the CPUs to downclock to roughly half speed under sustained load. The
> regression is visible both during boot and when running CPU stress
> workloads such as stress-ng: the CPUs initially ramp up to the expected
> frequency, then drop to a lower OPP even though the system is clearly
> CPU-bound.
> 
> Bisecting points to this commit and reverting it restores the expected
> behaviour on the DragonBoard 820c - the CPUs track the cpufreq policy
> and run at full performance under load.
> 
> The exact interaction with the ACD is not yet fully understood and we
> would like to keep ACD in use to avoid possible SoC reliability issues.
> Until we have a better fix that preserves ACD while avoiding this
> performance regression, revert the bisected patch to restore the
> previous behaviour.
> 
> Fixes: b3b274bc9d3d ("clk: qcom: cpu-8996: simplify the cpu_clk_notifier_cb")
> Cc: stable@...r.kernel.org # v6.3+
> Link: https://lore.kernel.org/linux-arm-msm/20230113120544.59320-8-dmitry.baryshkov@linaro.org/
> Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> Signed-off-by: Christopher Obbard <christopher.obbard@...aro.org>
> ---

It may be that your board really has a MSM/APQ8x96*SG* which is another
name for the PRO SKU, which happens to have a 2 times wider divider, try

`cat /sys/bus/soc/devices/soc0/soc_id`

see:

https://lore.kernel.org/linux-arm-msm/20251111-db820c-pro-v1-0-6eece16c5c23@oss.qualcomm.com/

https://lore.kernel.org/linux-arm-msm/kXrAkKv7RZct22X0wivLWqOAiLKpFuDCAY1KY_KSx649kn7BNmJ2IFFMrsYPAyDlcxIjbQCQ1PHb5KaNFawm9IGIXUbch-DI9OI_l73BAaM=@protonmail.com/

Konrad