From e55d86f654aa9dd4951b441636c8ca4b37786daf Mon Sep 17 00:00:00 2001
From: Eric Anholt <eric@anholt.net>
Date: Tue, 26 Feb 2008 12:26:23 -0800
Subject: [PATCH] Fix SDVO I2C access on Mac Mini in EFI mode.

The GMBUS was being left in SDVO pin access mode, which blocked our bit-banging
access to those pins.  Thanks to Peter Jones for quick debugging turnaround
in getting this fixed.
---
 src/i810_reg.h | 8 ++++++++
 src/i830_i2c.c | 7 +++++++
 2 files changed, 15 insertions(+)

diff --git a/src/i810_reg.h b/src/i810_reg.h
index 9eeddc9b..d5b6805e 100644
--- a/src/i810_reg.h
+++ b/src/i810_reg.h
@@ -290,6 +290,14 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 # define GPIO_DATA_VAL_IN		(1 << 12)
 # define GPIO_DATA_PULLUP_DISABLE	(1 << 13)
 
+/* GMBus registers for hardware-assisted (non-bitbanging) I2C access */
+#define GMBUS0			0x5100
+#define GMBUS1			0x5104
+#define GMBUS2			0x5108
+#define GMBUS3			0x510c
+#define GMBUS4			0x5110
+#define GMBUS5			0x5120
+
 /* p317, 319
  */
 #define VCLK2_VCO_M        0x6008 /* treat as 16 bit? (includes msbs) */
diff --git a/src/i830_i2c.c b/src/i830_i2c.c
index d80229d5..33a75a81 100644
--- a/src/i830_i2c.c
+++ b/src/i830_i2c.c
@@ -346,6 +346,7 @@ Bool
 I830I2CInit(ScrnInfoPtr pScrn, I2CBusPtr *bus_ptr, int i2c_reg, char *name)
 {
     I2CBusPtr pI2CBus;
+    I830Ptr pI830 = I830PTR(pScrn);
 
     pI2CBus = xf86CreateI2CBusRec();
 
@@ -379,6 +380,12 @@ I830I2CInit(ScrnInfoPtr pScrn, I2CBusPtr *bus_ptr, int i2c_reg, char *name)
     pI2CBus->AcknTimeout = 40;
     pI2CBus->RiseFallTime = 20;
 
+    /* Disable the GMBUS, which we won't use.  If it is left enabled (for
+     * example, by Mac Mini EFI initialization), GPIO access to the pins it
+     * uses gets disabled.
+     */
+    OUTREG(GMBUS0, 0);
+
     if (!xf86I2CBusInit(pI2CBus))
 	return FALSE;