drm/i915: Improve CRTDDC mapping by using VBT info

Use VBT information to determine which DDC bus to use for CRTDCC.
Fall back to GPIOA if VBT info is not available.

Signed-off-by: David Müller <d.mueller@elsoft.ch>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Tested on: 855 (David), and 945GM, 965GM, GM45, and G45 (anholt)

drivers/gpu/drm/i915/i915_drv.h

@@ -222,6 +222,7 @@ typedef struct drm_i915_private {
 	unsigned int edp_support:1;
 	int lvds_ssc_freq;
 
+	int crt_ddc_bus; /* -1 = unknown, else GPIO to use for CRT DDC */
 	struct drm_i915_fence_reg fence_regs[16]; /* assume 965 */
 	int fence_reg_start; /* 4 if userland hasn't ioctl'd us yet */
 	int num_fence_regs; /* 8 on pre-965, 16 otherwise */

drivers/gpu/drm/i915/intel_bios.c

@@ -59,6 +59,16 @@ find_section(struct bdb_header *bdb, int section_id)
 	return NULL;
 }
 
+static u16
+get_blocksize(void *p)
+{
+	u16 *block_ptr, block_size;
+
+	block_ptr = (u16 *)((char *)p - 2);
+	block_size = *block_ptr;
+	return block_size;
+}
+
 static void
 fill_detail_timing_data(struct drm_display_mode *panel_fixed_mode,
 			struct lvds_dvo_timing *dvo_timing)
@@ -214,6 +224,41 @@ parse_general_features(struct drm_i915_private *dev_priv,
 	}
 }
 
+static void
+parse_general_definitions(struct drm_i915_private *dev_priv,
+			  struct bdb_header *bdb)
+{
+	struct bdb_general_definitions *general;
+	const int crt_bus_map_table[] = {
+		GPIOB,
+		GPIOA,
+		GPIOC,
+		GPIOD,
+		GPIOE,
+		GPIOF,
+	};
+
+	/* Set sensible defaults in case we can't find the general block
+	   or it is the wrong chipset */
+	dev_priv->crt_ddc_bus = -1;
+
+	general = find_section(bdb, BDB_GENERAL_DEFINITIONS);
+	if (general) {
+		u16 block_size = get_blocksize(general);
+		if (block_size >= sizeof(*general)) {
+			int bus_pin = general->crt_ddc_gmbus_pin;
+			DRM_DEBUG("crt_ddc_bus_pin: %d\n", bus_pin);
+			if ((bus_pin >= 1) && (bus_pin <= 6)) {
+				dev_priv->crt_ddc_bus =
+					crt_bus_map_table[bus_pin-1];
+			}
+		} else {
+			DRM_DEBUG("BDB_GD too small (%d). Invalid.\n",
+				  block_size);
+		}
+	}
+}
+
 static void
 parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
 		       struct bdb_header *bdb)
@@ -222,7 +267,7 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
 	struct bdb_general_definitions *p_defs;
 	struct child_device_config *p_child;
 	int i, child_device_num, count;
-	u16	block_size, *block_ptr;
+	u16	block_size;
 
 	p_defs = find_section(bdb, BDB_GENERAL_DEFINITIONS);
 	if (!p_defs) {
@@ -240,8 +285,7 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
 		return;
 	}
 	/* get the block size of general definitions */
-	block_ptr = (u16 *)((char *)p_defs - 2);
+	block_size = get_blocksize(p_defs);
-	block_size = *block_ptr;
 	/* get the number of child device */
 	child_device_num = (block_size - sizeof(*p_defs)) /
 				sizeof(*p_child);
@@ -362,6 +406,7 @@ intel_init_bios(struct drm_device *dev)
 
 	/* Grab useful general definitions */
 	parse_general_features(dev_priv, bdb);
+	parse_general_definitions(dev_priv, bdb);
 	parse_lfp_panel_data(dev_priv, bdb);
 	parse_sdvo_panel_data(dev_priv, bdb);
 	parse_sdvo_device_mapping(dev_priv, bdb);

drivers/gpu/drm/i915/intel_crt.c

@@ -508,6 +508,7 @@ void intel_crt_init(struct drm_device *dev)
 {
 	struct drm_connector *connector;
 	struct intel_output *intel_output;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 i2c_reg;
 
 	intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
@@ -527,8 +528,12 @@ void intel_crt_init(struct drm_device *dev)
 	/* Set up the DDC bus. */
 	if (IS_IGDNG(dev))
 		i2c_reg = PCH_GPIOA;
-	else
+	else {
 		i2c_reg = GPIOA;
+		/* Use VBT information for CRT DDC if available */
+		if (dev_priv->crt_ddc_bus != -1)
+			i2c_reg = dev_priv->crt_ddc_bus;
+	}
 	intel_output->ddc_bus = intel_i2c_create(dev, i2c_reg, "CRTDDC_A");
 	if (!intel_output->ddc_bus) {
 		dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "