Re: [RFC 3/3] drm/amd: Return -EBUSY for amdgpu_pmops_thaw() on success

["Mario Limonciello (AMD) (kernel.org)" <superm1@kernel.org>]

On 10/20/2025 12:21 PM, Rafael J. Wysocki wrote:
> On Mon, Oct 20, 2025 at 6:53 PM Mario Limonciello (AMD)
> <superm1@kernel.org> wrote:
>>
>> From: Mario Limonciello <mario.limonciello@amd.com>
>>
>> The PM core should be notified that thaw was skipped for the device
>> so that if it's tried to be resumed (such as an aborted hibernate)
>> that it gets another chance to resume.
>>
>> Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> index 61268aa82df4d..d40af069f24dd 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> @@ -2681,7 +2681,7 @@ static int amdgpu_pmops_thaw(struct device *dev)
>>
>>          /* do not resume device if it's normal hibernation */
>>          if (!pm_hibernate_is_recovering() && !pm_hibernation_mode_is_suspend())
>> -               return 0;
>> +               return -EBUSY;
> 
> So that's why you need the special handling of -EBUSY in the previous patch.

Yup.

> 
> I think that you need to save some state in this driver and then use
> it in subsequent callbacks instead of hacking the core to do what you
> want.
> 

The problem is the core decides "what" to call and more importantly 
"when" to call it.

IE if the core thinks that something is thawed it will never call 
resume, and that's why you end up in a bad place with Muhammad's 
cancellation series and why I proposed this one to discuss.

We could obviously go back to dropping this case entirely:

if (!pm_hibernate_is_recovering() && !pm_hibernation_mode_is_suspend())

But then the display turns on at thaw(), you do an unnecessary resource 
eviction, it takes a lot longer if you have a ton of VRAM etc.