drm/i915: use GMBUS to manage i2c links

Use the GMBUS interface rather than direct bit banging to grab the EDID
over DDC (and for other forms of auxiliary communication with external
display controllers). The hope is that this method will be much faster
and more reliable than bit banging for fetching EDIDs from buggy monitors
or through switches, though we still preserve the bit banging as a
fallback in case GMBUS fails.

Based on an original patch by Jesse Barnes.

Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 4 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 8986a4b898db..d11bbcad4fea 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -291,14 +291,6 @@ 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,
-        };
 
         general = find_section(bdb, BDB_GENERAL_DEFINITIONS);
         if (general) {
@@ -306,10 +298,8 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
                 if (block_size >= sizeof(*general)) {
                         int bus_pin = general->crt_ddc_gmbus_pin;
                         DRM_DEBUG_KMS("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];
-                        }
+                        if (bus_pin >= 1 && bus_pin <= 6)
+                                dev_priv->crt_ddc_pin = bus_pin - 1;
                 } else {
                         DRM_DEBUG_KMS("BDB_GD too small (%d). Invalid.\n",
                                   block_size);
@@ -533,6 +523,8 @@ intel_init_bios(struct drm_device *dev)
         struct bdb_header *bdb = NULL;
         u8 __iomem *bios = NULL;
 
+        dev_priv->crt_ddc_pin = GMBUS_PORT_VGADDC;
+
         /* XXX Should this validation be moved to intel_opregion.c? */
         if (dev_priv->opregion.vbt) {
                 struct vbt_header *vbt = dev_priv->opregion.vbt;