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

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Message-ID: <CAO9ioeVBk0CLGcdUdbixVGwGfheOaVwX=i39JovHa740mO4kRg@mail.gmail.com>
Date: Thu, 18 Dec 2025 15:33:45 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: 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>, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] Revert "clk: qcom: cpu-8996: simplify the cpu_clk_notifier_cb"

On Thu, 18 Dec 2025 at 15:09, Konrad Dybcio
<konrad.dybcio@....qualcomm.com> wrote:
>
> On 12/17/25 5:39 PM, Dmitry Baryshkov wrote:
> > On Wed, Dec 17, 2025 at 01:22:59PM +0100, Konrad Dybcio wrote:
> >> On 12/14/25 8:26 PM, Christopher Obbard wrote:
> >>> Hi Konrad,
> >>>
> >>> On Mon, 8 Dec 2025 at 22:36, Christopher Obbard
> >>> <christopher.obbard@...aro.org> wrote:
> >>>> Apologies for the late response, I was in the process of setting some
> >>>> more msm8096 boards up again in my new workspace to test this
> >>>> properly.
> >>>>
> >>>>
> >>>>> 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`
> >>>>
> >>>> I read the soc_id from both of the msm8096 boards I have:
> >>>>
> >>>> Open-Q™ 820 µSOM Development Kit (APQ8096)
> >>>> ```
> >>>> $ cat /sys/bus/soc/devices/soc0/soc_id
> >>>> 291
> >>>> ```
> >>>> (FWIW this board is not in mainline yet; but boots with a DT similar
> >>>> enough to the db820c. I have a patch in my upstream backlog enabling
> >>>> that board; watch this space)
> >>>>
> >>>> DragonBoard™ 820c (APQ8096)
> >>>> ```
> >>>> $ cat /sys/bus/soc/devices/soc0/soc_id
> >>>> 291
> >>>> ```
> >>>
> >>> Sorry to nag, but are you able to look into this soc_id and see if
> >>> it's the PRO SKU ?
> >>
> >> No, it's the "normal" one
> >>
> >> Maybe Dmitry would know a little more what's going on
> >
> > Unfortunately, no.
> >
> > Maybe, the best option would be to really land the revert.
> >
> >
> > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>
> Is there a chance that this removal:
>
> -       case POST_RATE_CHANGE:
> -               if (cnd->new_rate < DIV_2_THRESHOLD)
> -                       ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw,
> -                                                          SMUX_INDEX);
> -               else
> -                       ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw,
> -                                                          ACD_INDEX);
>
> could have been the cause?
>
> On one hand, we're removing this explicit "set ACD as parent" path, but
> OTOH determine_rate should have taken care of this..

My idea was that we switch to SMUX temporarily, then CLK framework
fixes that for us while performing the actual reparenting.

Christopher, as a quick check, could possibly revert just this chunk?


-- 
With best wishes
Dmitry