[ 55/71] drm/radeon/dpm/rs780: dont enable sclk scaling if not required

[Greg Kroah-Hartman]

3.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alex Deucher <alexander.deucher@xxxxxxx>

commit e40210cca98068835acd5a4fe760bf96b3a1aa48 upstream.

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@xxxxxxx>
Reviewed-by: Christian KÃnig <christian.koenig@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/radeon/rs780_dpm.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/gpu/drm/radeon/rs780_dpm.c
+++ b/drivers/gpu/drm/radeon/rs780_dpm.c
@@ -486,6 +486,9 @@ static void rs780_activate_engine_clk_sc
 	    (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);
 }
 


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