drm/radeon/ci: disable mclk switching for high refresh rates (v2)

[ Upstream commit 58d7e3e4 ]

Even if the vblank period would allow it, it still seems to
be problematic on some cards.

v2: fix logic inversion (Nils)

bug: https://bugs.freedesktop.org/show_bug.cgi?id=96868

Cc: stable@vger.kernel.org
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

drivers/gpu/drm/radeon/ci_dpm.c

@@ -776,6 +776,12 @@ bool ci_dpm_vblank_too_short(struct radeon_device *rdev)
 	u32 vblank_time = r600_dpm_get_vblank_time(rdev);
 	u32 switch_limit = pi->mem_gddr5 ? 450 : 300;
 
+	/* disable mclk switching if the refresh is >120Hz, even if the
+        * blanking period would allow it
+        */
+	if (r600_dpm_get_vrefresh(rdev) > 120)
+		return true;
+
 	if (vblank_time < switch_limit)
 		return true;
 	else