Re: [PATCH v1 00/30] Introduce core voltage scaling for NVIDIA Tegra20/30 SoCs

Dmitry Osipenko
2020-11-09T05:10:23Z

09.11.2020 07:47, Dmitry Osipenko пишет:
> 09.11.2020 07:43, Viresh Kumar пишет:
>> On 08-11-20, 15:19, Dmitry Osipenko wrote:
>>> I took a detailed look at the GENPD and tried to implement it. Here is
>>> what was found:
>>>
>>> 1. GENPD framework doesn't aggregate performance requests from the
>>> attached devices. This means that if deviceA requests performance state
>>> 10 and then deviceB requests state 3, then framework will set domain's
>>> state to 3 instead of 10.
>>
>> It does. Look at _genpd_reeval_performance_state().
>>
>
> Thanks, I probably had a bug in the quick prototype and then overlooked
> that function.
>

If a non-hardware device-tree node is okay to have for the domain, then
I can try again.

What I also haven't mentioned is that GENPD adds some extra complexity
to some drivers (3d, video decoder) because we will need to handle both
new GENPD and legacy Tegra specific pre-genpd era domains.

I'm also not exactly sure how the topology of domains should look like
because Tegra has a power-controller (PMC) which manages power rail of a
few hardware units. Perhaps it should be

device -> PMC domain -> CORE domain

but not exactly sure for now.