drm/amd/display: Drop dm_prepare_suspend() and dm_complete()

[Why]
dm_prepare_suspend() was added in commit 50e0bae
("drm/amd/display: Add and use new dm_prepare_suspend() callback")
to allow display to turn off earlier in the suspend sequence.

This caused a regression that HDMI audio sometimes didn't work
properly after resume unless audio was playing during suspend.

[How]
Drop dm_prepare_suspend() callback. All code in it will still run
during dm_suspend(). Also drop unnecessary dm_complete() callback.
dm_complete() was used for failed prepare and also for any case
of successful resume.  The code in it already runs in dm_resume().

This change will introduce more time that the display is turned on
during suspend sequence. The compositor can turn it off sooner if
desired.

Cc: Harry Wentland <harry.wentland@amd.com>
Reported-by: Przemysław Kopa <prz.kopa@gmail.com>
Closes: https://lore.kernel.org/amd-gfx/1cea0d56-7739-4ad9-bf8e-c9330faea2bb@kernel.org/T/#m383d9c08397043a271b36c32b64bb80e524e4b0f
Reported-by: Kalvin <hikaph+oss@gmail.com>
Closes: alsa-project/alsa-lib#465
Closes: https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/4809
Fixes: 50e0bae ("drm/amd/display: Add and use new dm_prepare_suspend() callback")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: superm1

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -3182,25 +3182,6 @@ static void dm_destroy_cached_state(struct amdgpu_device *adev)
 	dm->cached_state = NULL;
 }
 
-static void dm_complete(struct amdgpu_ip_block *ip_block)
-{
-	struct amdgpu_device *adev = ip_block->adev;
-
-	dm_destroy_cached_state(adev);
-}
-
-static int dm_prepare_suspend(struct amdgpu_ip_block *ip_block)
-{
-	struct amdgpu_device *adev = ip_block->adev;
-
-	if (amdgpu_in_reset(adev))
-		return 0;
-
-	WARN_ON(adev->dm.cached_state);
-
-	return dm_cache_state(adev);
-}
-
 static int dm_suspend(struct amdgpu_ip_block *ip_block)
 {
 	struct amdgpu_device *adev = ip_block->adev;
@@ -3626,10 +3607,8 @@ static const struct amd_ip_funcs amdgpu_dm_funcs = {
 	.early_fini = amdgpu_dm_early_fini,
 	.hw_init = dm_hw_init,
 	.hw_fini = dm_hw_fini,
-	.prepare_suspend = dm_prepare_suspend,
 	.suspend = dm_suspend,
 	.resume = dm_resume,
-	.complete = dm_complete,
 	.is_idle = dm_is_idle,
 	.wait_for_idle = dm_wait_for_idle,
 	.check_soft_reset = dm_check_soft_reset,