On 2025-10-14 17:38, Mario Limonciello wrote:
>
>
> On 10/14/2025 4:27 PM, Alex Deucher wrote:
>> On Tue, Oct 14, 2025 at 3:46 PM Mario Limonciello
>> <[email protected]> wrote:
>>>
>>> [Why]
>>> If userspace hasn't frozen user processes (like systemd does with
>>> user.slice) then an aborted hibernate could give control back to
>>> userspace before display hardware is resumed. IoW an atomic commit could
>>> be done while the hardware is in D3, which could hang a system.
>>
>> Is there any way to prevent this altogether?
>
> The obvious way is that userspace should be freezing user processes. That's
> what systemd does.
>
>> This seems like a recipe
>> for trouble for any driver.
>
> If we want to uplevel this kind of check I think we would need some helper to
> report hardware status into drm and drm would have to call that.
>
> Most distros use systemd, and this only happened in an aborted hibernate. I
> guess I'd like to see how much this warning actually comes up before deciding
> if all that plumbing is worth it.
I was briefly thinking about a generic solution as well and don't
think it's worth it at this point. This is mostly about internal
driver/HW state.
Harry
>>
>> Alex
>>
>>>
>>> [How]
>>> Add a check whether the IP block hardware is ready to the atomic check
>>> handler and return a failure. Userspace shouldn't do an atomic commit if
>>> the atomic check fails.
>>>
>>> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4627
>>> Signed-off-by: Mario Limonciello <[email protected]>
>>> ---
>>> Cc: Harry Wentland <[email protected]>
>>> v2:
>>> * Return -EBUSY instead (Harry)
>>> ---
>>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++
>>> 1 file changed, 5 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> index 6446ec6c21d4..f5cd9982af99 100644
>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> @@ -12010,6 +12010,11 @@ static int amdgpu_dm_atomic_check(struct
>>> drm_device *dev,
>>>
>>> trace_amdgpu_dm_atomic_check_begin(state);
>>>
>>> + if (WARN_ON(unlikely(!amdgpu_device_ip_is_hw(adev,
>>> AMD_IP_BLOCK_TYPE_DCE)))) {
>>> + ret = -EBUSY;
>>> + goto fail;
>>> + }
>>> +
>>> ret = drm_atomic_helper_check_modeset(dev, state);
>>> if (ret) {
>>> drm_dbg_atomic(dev, "drm_atomic_helper_check_modeset()
>>> failed\n");
>>> --
>>> 2.49.0
>>>
>
