drm/amd/display: Report to ACPI video if no panels were found

On desktop APUs amdgpu doesn't create a native backlight device
as no eDP panels are found.  However if the BIOS has reported
backlight control methods in the ACPI tables then an acpi_video0
backlight device will be made 8 seconds after boot.

This has manifested in a power slider on a number of desktop APUs
ranging from Ryzen 5000 through Ryzen 7000 on various motherboard
manufacturers. To avoid this, report to the acpi video detection
that the system does not have any panel connected in the native
driver.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1783786
Reported-by: Hans de Goede <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>
Reviewed-by: Hans de Goede <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: superm1

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

@@ -4360,6 +4360,10 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
 		amdgpu_set_panel_orientation(&aconnector->base);
 	}
 
+	/* If we didn't find a panel, notify the acpi video detection */
+	if (dm->adev->flags & AMD_IS_APU && dm->num_of_edps == 0)
+		acpi_video_report_nolcd();
+
 	/* Software is initialized. Now we can register interrupt handlers. */
 	switch (adev->asic_type) {
 #if defined(CONFIG_DRM_AMD_DC_SI)