Re: [PATCH v5 2/4] soc: qcom: ice: Add OPP-based clock scaling support for ICE

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 2/20/26 12:15 PM, Abhinaba Rakshit wrote:
> On Fri, Feb 20, 2026 at 10:42:58AM +0100, Konrad Dybcio wrote:
>> On 2/20/26 8:33 AM, Abhinaba Rakshit wrote:
>>> On Thu, Feb 19, 2026 at 03:20:31PM +0100, Konrad Dybcio wrote:
>>>> On 2/18/26 8:02 PM, Abhinaba Rakshit wrote:
>>>>> On Mon, Feb 16, 2026 at 01:18:57PM +0100, Konrad Dybcio wrote:
>>>>>> On 2/13/26 8:02 AM, Abhinaba Rakshit wrote:
>>>>>>> On Thu, Feb 12, 2026 at 12:30:00PM +0100, Konrad Dybcio wrote:
>>>>>>>> On 2/11/26 10:47 AM, Abhinaba Rakshit wrote:
>>>>>>>>> Register optional operation-points-v2 table for ICE device
>>>>>>>>> and aquire its minimum and maximum frequency during ICE
>>>>>>>>> device probe.
>>>>
>>>> [...]
>>>>
>>>>>>> However, my main concern was for the corner cases, where:
>>>>>>> (target_freq > max && ROUND_CEIL)
>>>>>>> and
>>>>>>> (target_freq < min && ROUND_FLOOR)
>>>>>>> In both the cases, the OPP APIs will fail and the clock remains unchanged.
>>>>>>
>>>>>> I would argue that's expected behavior, if the requested rate can not
>>>>>> be achieved, the "set_rate"-like function should fail
>>>>>>
>>>>>>> Hence, I added the checks to make the API as generic/robust as possible.
>>>>>>
>>>>>> AFAICT we generally set storage_ctrl_rate == ice_clk_rate with some slight
>>>>>> play, but the latter never goes above the FMAX of the former
>>>>>>
>>>>>> For the second case, I'm not sure it's valid. For "find lowest rate" I would
>>>>>> expect find_freq_*ceil*(rate=0). For other cases of scale-down I would expect
>>>>>> that we want to keep the clock at >= (or ideally == )storage_ctrl_clk anyway
>>>>>> so I'm not sure _floor() is useful
>>>>>
>>>>> Clear, I guess, the idea is to ensure ice-clk <= storage-clk in case of scale_up
>>>>> and ice-clk >= storage-clk in case of scale_down.
>>>>
>>>> I don't quite understand the first case (ice <= storage for scale_up), could you
>>>> please elaborate?
>>>
>>> Here I basically mean to say is that, as you mentioned "we generally set
>>> storage_ctrl_rate == ice_clk_rate, but latter never goes above the FMAX of the former".
>>> I guess, the ideal way to handle this is to ensure using _floor when we want to scale_up.
>>> This ensures the ice_clk does not vote for more that what storage_ctrl is running on.
>>
>> Right, but what I was asking specifically is why we don't want that to happen
> 
> I would argue saying that, having ice_clk higher than storage_ctrl_clk does
> not makes sense, as it will not improve the throughput since the controller
> clock rate will still be a bottle-neck and it will surely drain more power.

Got it

Konrad