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

BugLink: http://bugs.launchpad.net/bugs/1698799

commit 0a646f33 upstream.

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=96868Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/gpu/drm/amd/amdgpu/ci_dpm.c

@@ -894,6 +894,12 @@ static bool ci_dpm_vblank_too_short(struct amdgpu_device *adev)
 	u32 vblank_time = amdgpu_dpm_get_vblank_time(adev);
 	u32 switch_limit = adev->mc.vram_type == AMDGPU_VRAM_TYPE_GDDR5 ? 450 : 300;
 
+	/* disable mclk switching if the refresh is >120Hz, even if the
+	 * blanking period would allow it
+	 */
+	if (amdgpu_dpm_get_vrefresh(adev) > 120)
+		return true;
+
 	if (vblank_time < switch_limit)
 		return true;
 	else