drm/radeon/dpm/rs780: don't enable sclk scaling if not required

If the low and high sclks are the same, there is no need to
enable sclk scaling.  This causes display stability issues on
certain boards.

Fixes:
https://bugzilla.kernel.org/show_bug.cgi?id=60857

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

diff --git a/drivers/gpu/drm/radeon/rs780_dpm.c b/drivers/gpu/drm/radeon/rs780_dpm.c
index 31487ce..eb336bf 100644 (file)
--- a/drivers/gpu/drm/radeon/rs780_dpm.c
+++ b/drivers/gpu/drm/radeon/rs780_dpm.c
@@ -499,6 +499,9 @@ static void rs780_activate_engine_clk_scaling(struct radeon_device *rdev,
            (new_state->sclk_low == old_state->sclk_low))
                return;
 
+       if (new_state->sclk_high == new_state->sclk_low)
+               return;
+
        rs780_clk_scaling_enable(rdev, true);
 }