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

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Message-ID: <5e255831-3e84-4f3f-8b4f-c66d05e6be09@oss.qualcomm.com>
Date: Thu, 18 Dec 2025 14:09:24 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....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 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..

Konrad