Re: [EXT] Re: [PATCH] pmdomain: arm: scmi_pm_domain: Initialize state as off

[Sudeep Holla]

Hi Ranjani,

On Mon, Jan 13, 2025 at 07:54:06PM +0000, Ranjani Vaidyanathan wrote:
> Hello Sudeep,
>
> Will try to explain the situation we are facing.
> 1. We have multiple agents running, Agent-A is booted up first before Linux
> is booted and powers up a shared power domain PD-X.
> 2. Linux boots and gets the power state of PD-X. And its already ON. And
> then PD -X is initialized with a default ON state.
> 3. When the driver that needs PD-X  is probed, Linux sees that the power
> domain status is ON and never makes an SCMI call to power up the PD-X for
> Linux Agent.
> 4. Agent-A now is shutdown/suspends. Linux will crash because the platform
> disables PD-X because it has no other requests for PD-X.
>

Thanks for the detailed explanation. I understand the issue now.

I would like to discuss if the below alternative approach works for you.
We can debate the pros and cons. I see with the approach in this patch
proposed by Peng we would avoid querying and setting genpd all together
during the genpd initialisation which is good. But if there are any genpd
left on by the platform or bootloader(same agent), it will not get turned
off when Linux tries to turn off the unused genpds(IIRC this could be the
reason for the current state of code). While your platform may find sending
those commands unnecessary, there was some usecase where SCMI platform kept
all resources ON by default for faster boot and expects OSPM to turn off
unused resources. So we need to support both the cases. I hope my below
patch should suffice.

Regards,
Sudeep

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