Re: [PATCH 1/3] PM: domains: Drop the performance state vote for a device at detach

On Thu, 9 Sept 2021 at 15:48, Dmitry Osipenko [off-list ref] wrote:

07.09.2021 13:16, Ulf Hansson пишет:
...

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Also note that a very similar problem exists, *before* the device gets
attached in the first place. More precisely, nothing prevents the
performance state from being set to a non-compatible value for an
always-on HW/device that hasn't been attached yet. So maybe you need
to set the maximum performance state at genpd initializations, then
use the ->sync_state() callback to very that all consumers have been
attached to the genpd provider, before allowing the state to be
changed/lowered?

That is already done by the PD driver.

https://elixir.bootlin.com/linux/latest/source/drivers/soc/tegra/pmc.c#L3790

Yes, I already knew that, but forgot it. :-) Thanks for the pointer.
Let me rethink the approach.

In a way, it kind of sounds like this is a generic problem - so
perhaps we should think of adding a ->withdraw_sync_state() callback
that can be assigned by provider drivers, to get informed when a
consumer driver is getting unbinded.

Not sure, doesn't feel to me that this is necessary for today. A bit too
cumbersome for a simple sanity-check, IMO.

Maybe, but I can bring it up with the fw_devlinks people to see what they think.

In any case, we should not move forward with $subject patch as is.

Let me think about it.

Kind regards
Uffe

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