[Intel-gfx] [PATCH 1/4] drm/i915: gen7: implement rczunit workaround

[Kenneth Graunke]

From: Eugeni Dodonov <eugeni.dodonov at intel.com>

This is yet another workaround related to clock gating which we need on
Ivy Bridge.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41353
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44610
Tested-by: Eugeni Dodonov <eugeni.dodonov at intel.com>
Signed-off-by: Eugeni Dodonov <eugeni.dodonov at intel.com>
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 drivers/gpu/drm/i915/i915_reg.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |    5 +++++
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index c3afb78..80fd6b5 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3618,6 +3618,7 @@
 #define    GT_FIFO_NUM_RESERVED_ENTRIES		20
 
 #define GEN6_UCGCTL2				0x9404
+# define GEN6_RCZUNIT_CLOCK_GATE_DISABLE		(1 << 13)
 # define GEN6_RCPBUNIT_CLOCK_GATE_DISABLE		(1 << 12)
 # define GEN6_RCCUNIT_CLOCK_GATE_DISABLE		(1 << 11)
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f1744aa..070c946 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8461,6 +8461,11 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(WM2_LP_ILK, 0);
 	I915_WRITE(WM1_LP_ILK, 0);
 
+	/* According to the spec, bit 13 (RCZUNIT) must be set on IVB.
+	 * This implements the WaDisableRCZUnitClockGating workaround.
+	 */
+	I915_WRITE(GEN6_UCGCTL2, GEN6_RCZUNIT_CLOCK_GATE_DISABLE);
+
 	I915_WRITE(ILK_DSPCLK_GATE, IVB_VRHUNIT_CLK_GATE);
 
 	I915_WRITE(IVB_CHICKEN3,
-- 
1.7.7.1