From e40210cca98068835acd5a4fe760bf96b3a1aa48 Mon Sep 17 00:00:00 2001
From: Alex Deucher <alexander.deucher@amd.com>
Date: Fri, 13 Sep 2013 10:55:10 -0400
Subject: drm/radeon/dpm/rs780: don't enable sclk scaling if not required
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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
--- 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);
 }
 
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