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 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

> Also, this avoids the corner case, where target_freq provided is higher that the supporter
> rates (descriped in ICE OPP-table) for ICE, using _ceil makes no sense.

This is potentially a valid concern, do we have cases of storage_clk > ice_clk?

Konrad