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

[Abhinaba Rakshit]

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.
 
> > 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?

As of now, on the UFS storages (targets KLMT) I dont see the
storage_clk (FMAX) > ice_clk (FMAX). They are mostly equal.
However, I am not sure, about all the other targets and cannot
call the same will persist on the upcommings as well.

Abhinaba Rakshit