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

[Konrad Dybcio]

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.

[...]

>>> +	if (!ice->has_opp)
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	/* Clamp the freq to max if target_freq is beyond supported frequencies */
>>> +	if (ice->max_freq && target_freq >= ice->max_freq) {
>>> +		ice_freq = ice->max_freq;
>>> +		goto scale_clock;
>>> +	}
>>> +
>>> +	/* Clamp the freq to min if target_freq is below supported frequencies */
>>> +	if (ice->min_freq && target_freq <= ice->min_freq) {
>>> +		ice_freq = ice->min_freq;
>>> +		goto scale_clock;
>>> +	}
>>
>> The OPP framework won't let you overclock the ICE if this is what these checks
>> are about. Plus the clk framework will perform rounding for you too
> 
> Right, maybe I can just add a check for 0 freq just to ensure the export API is
> not miss used.
> Something shown below:
> 
> if (!target_freq)
>     return -EINVAL;
> 
> 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

> 
> Please let me know, your thoughts.
> 
>>> +
>>> +	switch (flags) {
>>
>> Are you going to use these flags? Currently they're dead code
> 
> I agree, currently they are not used.
> However, since its an export API, I want to keep the rounding FLAGS
> support as it a common to have rounding flags in clock scaling APIs,
> and to support any future use-cases as well.

I think you have a bit of a misconception - yes, this is an export API and
should be designed with the consumers in mind, but then it's consumed by
in-tree modules only ("what's not on the list doesn't exist"), so it's actually
generally *discouraged* (with varying levels of emphasis) to add any code that
is not immediately useful, as these functions can be updated at any point in
time down the line

Konrad