Re: [PATCH 5/5] OPP: Remove custom OPP helper support

[Dmitry Osipenko]

On 6/27/22 10:19, Viresh Kumar wrote:
> On 27-06-22, 10:09, Dmitry Osipenko wrote:
>> Yes, I missed that multi-clock OPP patch, thanks.
>>
>> Seems _opp_compare_key() won't work properly for the multi-clocks since
>> Tegra doesn't have bandwidth nor level for the 3d OPPs. Why does it need
>> to check opp_table->clk_count == 1? Shouldn't it be opp_table->clk_count
>>> 0?
> 
> The problem is that when we have multiple clocks, we can't assume any
> of them as primary. Its the combination of the clock frequencies that
> make them unique. Otherwise, what will happen if we have same
> frequency of the first clock in two OPPs, but different frequency of
> the second clock.
> 
> Because of this, we won't also support multiple clocks in all freq
> finder APIs, like dev_pm_opp_find_freq_exact(). We can't do that from
> just one frequency.
> 
> Ideally, the drivers should now be calling dev_pm_opp_set_opp() to set
> the OPP now.
> 
> For your case, I think you can just add levels (like index) in the OPP
> table. So we can uniquely identify each OPP.
> 

What about to bump the "by-level" sorting priority, making it above the
"by-rate" sorting and then always use the first clock for the "by-rate"
sorting? Then the multi-clock will work for Tegra without breaking dtbs
and those for whom this sorting option won't be appropriate will have to
add levels to the DT.

-- 
Best regards,
Dmitry