Re: [RFC v2 01/11] OPP: Don't overwrite rounded clk rate

On 6/17/2019 9:20 AM, Viresh Kumar wrote:

On 14-06-19, 10:57, Viresh Kumar wrote:

...

Hmm, so this patch won't break anything and I am inclined to apply it again :)

Does anyone see any other issues with it, which I might be missing ?

I have updated the commit log a bit more to clarify on things, please let me know if it looks okay.

 opp: Don't overwrite rounded clk rate

 The OPP table normally contains 'fmax' values corresponding to the
 voltage or performance levels of each OPP, but we don't necessarily want
 all the devices to run at fmax all the time. Running at fmax makes sense
 for devices like CPU/GPU, which have a finite amount of work to do and
 since a specific amount of energy is consumed at an OPP, its better to
 run at the highest possible frequency for that voltage value.

 On the other hand, we have IO devices which need to run at specific
 frequencies only for their proper functioning, instead of maximum
 possible frequency.

 The OPP core currently roundup to the next possible OPP for a frequency
 and select the fmax value. To support the IO devices by the OPP core,
 lets do the roundup to fetch the voltage or performance state values,
 but not use the OPP frequency value. Rather use the value returned by
 clk_round_rate().

 The current user, cpufreq, of dev_pm_opp_set_rate() already does the
 rounding to the next OPP before calling this routine and it won't
 have any side affects because of this change.

Looks good to me. Should this also be documented someplace that dev_pm_opp_set_rate() would not be able to distinguish between its users trying to scale CPU/GPU's vs IO devices, so its the callers responsibility to round it accordingly before calling the API?

 Signed-off-by: Stephen Boyd <swboyd@chromium.org>
 Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
 [ Viresh: Massaged changelog and use temp_opp variable instead ]
 Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>