drm/i915: Fix DDC on some systems by clearing BIOS GMBUS setup.
This is a sync of a fix I made in the old UMS code. If the BIOS uses
the GMBUS and doesn't clear that setup, then our bit-banging I2C can
fail, leading to monitors not being detected.
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 6b59602..c4a2735 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -414,6 +414,13 @@
# define GPIO_DATA_VAL_IN (1 << 12)
# define GPIO_DATA_PULLUP_DISABLE (1 << 13)
+#define GMBUS0 0x5100
+#define GMBUS1 0x5104
+#define GMBUS2 0x5108
+#define GMBUS3 0x510c
+#define GMBUS4 0x5110
+#define GMBUS5 0x5120
+
/*
* Clock control & power management
*/
@@ -2166,6 +2173,13 @@
#define PCH_GPIOE 0xc5020
#define PCH_GPIOF 0xc5024
+#define PCH_GMBUS0 0xc5100
+#define PCH_GMBUS1 0xc5104
+#define PCH_GMBUS2 0xc5108
+#define PCH_GMBUS3 0xc510c
+#define PCH_GMBUS4 0xc5110
+#define PCH_GMBUS5 0xc5120
+
#define PCH_DPLL_A 0xc6014
#define PCH_DPLL_B 0xc6018