drm/radeon/dpm: implement force performance level for TN

Allows you to force the selected performance level via sysfs.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/trinity_smc.c b/drivers/gpu/drm/radeon/trinity_smc.c
index 85f86a2..a42d89f 100644
--- a/drivers/gpu/drm/radeon/trinity_smc.c
+++ b/drivers/gpu/drm/radeon/trinity_smc.c
@@ -73,6 +73,13 @@
 	return trinity_notify_message_to_smu(rdev, PPSMC_MSG_DPM_ForceState);
 }
 
+int trinity_dpm_n_levels_disabled(struct radeon_device *rdev, u32 n)
+{
+	WREG32_SMC(SMU_SCRATCH0, n);
+
+	return trinity_notify_message_to_smu(rdev, PPSMC_MSG_DPM_N_LevelsDisabled);
+}
+
 int trinity_uvd_dpm_config(struct radeon_device *rdev)
 {
 	return trinity_notify_message_to_smu(rdev, PPSMC_MSG_UVD_DPM_Config);