linux-kernel - Re: [PATCH] clk: qcom: gcc: Update the SDCC clock to use shared_floor

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Message-ID: <4023c6ba-7ff0-46e0-bb09-a0cd864441ac@oss.qualcomm.com>
Date: Thu, 9 Oct 2025 09:58:00 +0530
From: Taniya Das <taniya.das@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd
 <sboyd@...nel.org>, Dmitry Baryshkov <lumag@...nel.org>,
        Taniya Das <quic_tdas@...cinc.com>,
        Ajit Pandey <quic_ajipan@...cinc.com>,
        Imran Shaik <quic_imrashai@...cinc.com>,
        Jagadeesh Kona <quic_jkona@...cinc.com>, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: qcom: gcc: Update the SDCC clock to use
 shared_floor_ops



On 10/8/2025 5:56 PM, Konrad Dybcio wrote:
> On 9/26/25 11:41 AM, Taniya Das wrote:
>>
>>
>> On 8/8/2025 5:48 PM, Dmitry Baryshkov wrote:
>>> On Fri, Aug 08, 2025 at 02:51:50PM +0530, Taniya Das wrote:
>>>>
>>>>
>>>> On 8/7/2025 10:32 PM, Konrad Dybcio wrote:
>>>>> On 8/6/25 11:39 AM, Taniya Das wrote:
>>>>>>
>>>>>>
>>>>>> On 8/6/2025 3:00 PM, Konrad Dybcio wrote:
>>>>>>> On 8/6/25 11:27 AM, Taniya Das wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> On 8/5/2025 10:52 AM, Dmitry Baryshkov wrote:
>>>>>>>>> On Mon, Aug 04, 2025 at 11:59:21PM +0530, Taniya Das wrote:
>>>>>>>>>> gcc_sdcc2_apps_clk_src: rcg didn't update its configuration" during
>>>>>>>>>> boot. This happens due to the floor_ops tries to update the rcg
>>>>>>>>>> configuration even if the clock is not enabled.
>>>>>>>>>
>>>>>>>>> This has been working for other platforms (I see Milos, SAR2130P,
>>>>>>>>> SM6375, SC8280XP, SM8550, SM8650 using shared ops, all other platforms
>>>>>>>>> seem to use non-shared ops). What's the difference? Should we switch all
>>>>>>>>> platforms? Is it related to the hypervisor?
>>>>>>>>>
>>>>>>>>
>>>>>>>> If a set rate is called on a clock before clock enable, the
>>>>>>>
>>>>>>> Is this something we should just fix up the drivers not to do?
>>>>>>>
>>>>>>
>>>>>> I do not think CCF has any such limitation where the clock should be
>>>>>> enabled and then a clock rate should be invoked. We should handle it
>>>>>> gracefully and that is what we have now when the caching capabilities
>>>>>> were added in the code. This has been already in our downstream drivers.
>>>>>
>>>>> Should we do CFG caching on *all* RCGs to avoid having to scratch our
>>>>> heads over which ops to use with each clock individually?
>>>>>
>>>>
>>>> Yes, Konrad, that’s definitely the cleanest approach. If you're okay
>>>> with it, we can proceed with the current change first and then follow up
>>>> with a broader cleanup of the rcg2 ops. As part of that, we can also
>>>> transition the relevant SDCC clock targets to use floor_ops. This way,
>>>> we can avoid the rcg configuration failure logs in the boot sequence on
>>>> QCS615.
>>>
>>> the rcg2_shared_ops have one main usecase - parking of the clock to the
>>> safe source. If it is not required for the SDCC clock, then it is
>>> incorrect to land this patch.
>>
>> Along with the floor functionality we require parking of the clock to
>> safe source for SDCC clock. I am reusing the shared_floor_ops introduced
>> recently for SAR2130P explicitly for SDCC clocks.
>>
>>>
>>> If you are saying that we should be caching CFG value for all clock
>>> controllers, then we should change instead the clk_rcg2_ops.
>>>
>>
>> That is not required for all clock controllers and which ever clock
>> controller's clock requires it we use rcg2_shared_ops which was updated
>> to park the cfg.
> 
> I think Dmitry just wanted you to confirm that what you're doing in this
> patch is guided by the necessity of safe parking and not only to enable
> rcg caching
> 
> Konrad

Yes, that’s correct. The primary motivation for this patch is to ensure
safe parking, and the RCG caching is a secondary benefit.

-- 
Thanks,
Taniya Das