drm/radeon/dpm: add checks against vblank time

If the vblank time is too short to adjust mclk,
assume multiple displays (no mclk adjustments).

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index b468131..9b7025d 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -1678,6 +1678,7 @@
 		void (*print_power_state)(struct radeon_device *rdev, struct radeon_ps *ps);
 		void (*debugfs_print_current_performance_level)(struct radeon_device *rdev, struct seq_file *m);
 		int (*force_performance_level)(struct radeon_device *rdev, enum radeon_dpm_forced_level level);
+		bool (*vblank_too_short)(struct radeon_device *rdev);
 	} dpm;
 	/* pageflipping */
 	struct {
@@ -2446,6 +2447,7 @@
 #define radeon_dpm_print_power_state(rdev, ps) rdev->asic->dpm.print_power_state((rdev), (ps))
 #define radeon_dpm_debugfs_print_current_performance_level(rdev, m) rdev->asic->dpm.debugfs_print_current_performance_level((rdev), (m))
 #define radeon_dpm_force_performance_level(rdev, l) rdev->asic->dpm.force_performance_level((rdev), (l))
+#define radeon_dpm_vblank_too_short(rdev) rdev->asic->dpm.vblank_too_short((rdev))
 
 /* Common functions */
 /* AGP */