Re: [PATCH v7 0/6] clk/qcom: Support gdsc collapse polling using 'reset' interface

[Ulf Hansson]

On Thu, 1 Dec 2022 at 23:57, Bjorn Andersson <andersson@xxxxxxxxxx> wrote:
>
> On Wed, Oct 05, 2022 at 02:36:58PM +0530, Akhil P Oommen wrote:
> >
>
> @Ulf, Akhil has a power-domain for a piece of hardware which may be
> voted active by multiple different subsystems (co-processors/execution
> contexts) in the system.
>
> As such, during the powering down sequence we don't wait for the
> power-domain to turn off. But in the event of an error, the recovery
> mechanism relies on waiting for the hardware to settle in a powered off
> state.
>
> The proposal here is to use the reset framework to wait for this state
> to be reached, before continuing with the recovery mechanism in the
> client driver.

I tried to review the series (see my other replies), but I am not sure
I fully understand the consumer part.

More exactly, when and who is going to pull the reset and at what point?

>
> Given our other discussions on quirky behavior, do you have any
> input/suggestions on this?
>
> > Some clients like adreno gpu driver would like to ensure that its gdsc
> > is collapsed at hardware during a gpu reset sequence. This is because it
> > has a votable gdsc which could be ON due to a vote from another subsystem
> > like tz, hyp etc or due to an internal hardware signal. To allow
> > this, gpucc driver can expose an interface to the client driver using
> > reset framework. Using this the client driver can trigger a polling within
> > the gdsc driver.
>
> @Akhil, this description is fairly generic. As we've reached the state
> where the hardware has settled and we return to the client, what
> prevents it from being powered up again?
>
> Or is it simply a question of it hitting the powered-off state, not
> necessarily staying there?

Okay, so it's indeed the GPU driver that is going to assert/de-assert
the reset at some point. Right?

That seems like a reasonable approach to me, even if it's a bit
unclear under what conditions that could happen.

[...]

Kind regards
Uffe