[PATCH 3.12 071/144] drm/radeon/dpm: disable ss on Cayman

[Greg Kroah-Hartman]

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

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

From: Alex Deucher <alexander.deucher@xxxxxxx>

commit c745fe611ca42295c9d91d8e305d27983e9132ef upstream.

Spread spectrum seems to cause hangs when dynamic clock
switching is enabled.  Disable it for now. This does not
affect performance or the amount of power saved. Tracked
down by Martin Andersson.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=69723

Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/radeon/rv770_dpm.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/gpu/drm/radeon/rv770_dpm.c
+++ b/drivers/gpu/drm/radeon/rv770_dpm.c
@@ -2328,6 +2328,12 @@ void rv770_get_engine_memory_ss(struct r
 	pi->mclk_ss = radeon_atombios_get_asic_ss_info(rdev, &ss,
 						       ASIC_INTERNAL_MEMORY_SS, 0);
 
+	/* disable ss, causes hangs on some cayman boards */
+	if (rdev->family == CHIP_CAYMAN) {
+		pi->sclk_ss = false;
+		pi->mclk_ss = false;
+	}
+
 	if (pi->sclk_ss || pi->mclk_ss)
 		pi->dynamic_ss = true;
 	else


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