[Intel-gfx] [PATCH 1/2] IGD: workaround i2c bus issue in kernel side

[Shaohua Li]

In IGD, DPCUNIT_CLOCK_GATE_DISABLE bit should be set, otherwise i2c
access will be wrong.

Signed-off-by: Shaohua Li <shaohua.li at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |    5 +++++
 2 files changed, 6 insertions(+)

Index: linux/drivers/gpu/drm/i915/i915_reg.h
===================================================================
--- linux.orig/drivers/gpu/drm/i915/i915_reg.h	2009-03-16 14:18:27.000000000 +0800
+++ linux/drivers/gpu/drm/i915/i915_reg.h	2009-03-16 14:28:09.000000000 +0800
@@ -523,6 +523,7 @@
 #define   DPLLA_INPUT_BUFFER_ENABLE	(1 << 0)
 #define D_STATE		0x6104
 #define CG_2D_DIS	0x6200
+#define DPCUNIT_CLOCK_GATE_DISABLE	(1 << 24)
 #define CG_3D_DIS	0x6204
 
 /*
Index: linux/drivers/gpu/drm/i915/intel_display.c
===================================================================
--- linux.orig/drivers/gpu/drm/i915/intel_display.c	2009-03-16 14:16:11.000000000 +0800
+++ linux/drivers/gpu/drm/i915/intel_display.c	2009-03-16 14:27:46.000000000 +0800
@@ -1545,6 +1545,11 @@ static void intel_setup_outputs(struct d
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_connector *connector;
 
+	/* When using bit bashing for I2C, this bit needs to be set to 1 */
+	if (IS_IGD(dev))
+		I915_WRITE(CG_2D_DIS,
+			I915_READ(CG_2D_DIS) | DPCUNIT_CLOCK_GATE_DISABLE);
+
 	intel_crt_init(dev);
 
 	/* Set up integrated LVDS */