Re: [PATCH] drm/imagination: Convert to dev_pm_domain_{at,de}tach_list()

[Matt Coster <Matt.Coster@imgtec.com>]

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On 11/02/2026 19:17, Marek Vasut wrote:
> On 1/23/26 2:50 PM, Geert Uytterhoeven wrote:
> 
> Hello everyone,
> 
>> On Fri, 23 Jan 2026 at 14:36, Matt Coster <Matt.Coster@imgtec.com> wrote:
>>> On 22/01/2026 16:08, Geert Uytterhoeven wrote:
>>>> Call the dev_pm_domain_attach_list() and dev_pm_domain_detach_list()
>>>> helpers instead of open-coding multi PM Domain handling.
>>>>
>>>> This changes behavior slightly:
>>>>    - The new handling is also applied in case of a single PM Domain,
>>>>    - PM Domains are now referred to by index instead of by name, but
>>>>      "make dtbs_check" enforces the actual naming and ordering anyway,
>>>>    - There are no longer device links created between virtual domain
>>>>      devices, only between virtual devices and the parent device.
>>>
>>> We still need this guarantee, both at start and end of day. In the
>>> current implementation dev_pm_domain_attach_list() iterates forwards,
>>> but so does dev_pm_domain_detach_list(). Even if we changed that, I'd
>>> prefer not to rely on the implementation details when we can declare the
>>> dependencies explicitly.
>>
>> Note that on R-Car, the PM Domains are nested (see e.g. r8a7795_areas[]),
>> so they are always (un)powered in the correct order.  But that may not
>> be the case in the integration on other SoCs.
>>
>>> We had/have a patch (attached) kicking around internally to use the
>>> *_list() functions but keep the inter-domain links in place; it got held
>>> up by discussions as to whether we actually need those dependencies for
>>> the hardware to behave correctly. Your patch spurred me to run around
>>> the office and nag people a bit, and it seems we really do need to care
>>> about the ordering.
>>
>> OK.
>>
>>> Can you add the links back in for a V2 or I can properly send the
>>> attached patch instead, I don't mind either way.
>>
>> Please move forward with your patch, you are the expert.
>> I prefer not to be blamed for any breakage ;-)
> 
> Has there been any progress on fixing this kernel crash ?
> 
> There are already two proposed solutions, but no fix is upstream.
> 

Yes and no. Our patch to use dev_pm_domain_attach_list() has landed in
drm-misc-next as commit e19cc5ab347e3 ("drm/imagination: Use
dev_pm_domain_attach_list()"), but this does not fix the underlying
issue of missing synchronization in the PM core[1] is still unresolved
as far as I'm aware.

Cheers,
Matt

[1]: https://lore.kernel.org/r/CAMuHMdVOUzanEufhWqOL0nv81xCYh4YNAX_waG6y9PyUZ030tg@mail.gmail.com/

-- 
Matt Coster
E: matt.coster@imgtec.com

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