Revert "drm/amd: Keep display off while going into S4"

BugLink: https://bugs.launchpad.net/bugs/2115678
BugLink: https://bugs.launchpad.net/bugs/2121449

commit 7e7cb7a13c81073d38a10fa7b450d23712281ec4 upstream.

commit 68bfdc8dc0a1a ("drm/amd: Keep display off while going into S4")
attempted to keep displays off during the S4 sequence by not resuming
display IP.  This however leads to hangs because DRM clients such as the
console can try to access registers and cause a hang.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4155
Fixes: 68bfdc8dc0a1a ("drm/amd: Keep display off while going into S4")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://lore.kernel.org/r/20250522141328.115095-1-mario.limonciello@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit e485502c37b097b0bd773baa7e2741bf7bd2909a)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>

Author: superm1

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

@@ -3402,11 +3402,6 @@ static int dm_resume(struct amdgpu_ip_block *ip_block)
 
 		return 0;
 	}
-
-	/* leave display off for S4 sequence */
-	if (adev->in_s4)
-		return 0;
-
 	/* Recreate dc_state - DC invalidates it when setting power state to S3. */
 	dc_state_release(dm_state->context);
 	dm_state->context = dc_state_create(dm->dc, NULL);