drm/i915: Use the VBT from OpRegion when available (v3)

It is recommended that we use the Video BIOS tables that were copied
into the OpRegion during POST when initialising the driver. This saves
us from having to furtle around inside the ROM ourselves and possibly
allows the vBIOS to adjust the tables prior to initialisation.

On some systems, such as the Samsung N210, there is no accessible VBIOS
and the only means of finding the VBT is through the OpRegion.

v2: Rearrange the code so that ASLE is enabled along with ACPI
v3: Enable OpRegion parsing even without ACPI

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Garrett <mjg@redhat.com>

1 files changed, 42 insertions, 31 deletions

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 96f75d7..8d7deca 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -317,7 +317,7 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
 
 static void
 parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
-		       struct bdb_header *bdb)
+			  struct bdb_header *bdb)
 {
 	struct sdvo_device_mapping *p_mapping;
 	struct bdb_general_definitions *p_defs;
@@ -327,7 +327,7 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
 
 	p_defs = find_section(bdb, BDB_GENERAL_DEFINITIONS);
 	if (!p_defs) {
-		DRM_DEBUG_KMS("No general definition block is found\n");
+		DRM_DEBUG_KMS("No general definition block is found, unable to construct sdvo mapping.\n");
 		return;
 	}
 	/* judge whether the size of child device meets the requirements.
@@ -460,7 +460,7 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 
 	p_defs = find_section(bdb, BDB_GENERAL_DEFINITIONS);
 	if (!p_defs) {
-		DRM_DEBUG_KMS("No general definition block is found\n");
+		DRM_DEBUG_KMS("No general definition block is found, no devices defined.\n");
 		return;
 	}
 	/* judge whether the size of child device meets the requirements.
@@ -513,6 +513,7 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 	}
 	return;
 }
+
 /**
  * intel_init_bios - initialize VBIOS settings & find VBT
  * @dev: DRM device
@@ -520,11 +521,6 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
  * Loads the Video BIOS and checks that the VBT exists.  Sets scratch registers
  * to appropriate values.
  *
- * VBT existence is a sanity check that is relied on by other i830_bios.c code.
- * Note that it would be better to use a BIOS call to get the VBT, as BIOSes may
- * feed an updated VBT back through that, compared to what we'll fetch using
- * this method of groping around in the BIOS data.
- *
  * Returns 0 on success, nonzero on failure.
  */
 bool
@@ -532,31 +528,45 @@ intel_init_bios(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct pci_dev *pdev = dev->pdev;
-	struct vbt_header *vbt = NULL;
-	struct bdb_header *bdb;
-	u8 __iomem *bios;
-	size_t size;
-	int i;
-
-	bios = pci_map_rom(pdev, &size);
-	if (!bios)
-		return -1;
-
-	/* Scour memory looking for the VBT signature */
-	for (i = 0; i + 4 < size; i++) {
-		if (!memcmp(bios + i, "$VBT", 4)) {
-			vbt = (struct vbt_header *)(bios + i);
-			break;
-		}
+	struct bdb_header *bdb = NULL;
+	u8 __iomem *bios = NULL;
+
+	/* XXX Should this validation be moved to intel_opregion.c? */
+	if (dev_priv->opregion.vbt) {
+		struct vbt_header *vbt = dev_priv->opregion.vbt;
+		if (memcmp(vbt->signature, "$VBT", 4) == 0) {
+			DRM_DEBUG_DRIVER("Using VBT from OpRegion: %20s\n",
+					 vbt->signature);
+			bdb = (struct bdb_header *)((char *)vbt + vbt->bdb_offset);
+		} else
+			dev_priv->opregion.vbt = NULL;
 	}
 
-	if (!vbt) {
-		DRM_ERROR("VBT signature missing\n");
-		pci_unmap_rom(pdev, bios);
-		return -1;
-	}
+	if (bdb == NULL) {
+		struct vbt_header *vbt = NULL;
+		size_t size;
+		int i;
 
-	bdb = (struct bdb_header *)(bios + i + vbt->bdb_offset);
+		bios = pci_map_rom(pdev, &size);
+		if (!bios)
+			return -1;
+
+		/* Scour memory looking for the VBT signature */
+		for (i = 0; i + 4 < size; i++) {
+			if (!memcmp(bios + i, "$VBT", 4)) {
+				vbt = (struct vbt_header *)(bios + i);
+				break;
+			}
+		}
+
+		if (!vbt) {
+			DRM_ERROR("VBT signature missing\n");
+			pci_unmap_rom(pdev, bios);
+			return -1;
+		}
+
+		bdb = (struct bdb_header *)(bios + i + vbt->bdb_offset);
+	}
 
 	/* Grab useful general definitions */
 	parse_general_features(dev_priv, bdb);
@@ -568,7 +578,8 @@ intel_init_bios(struct drm_device *dev)
 	parse_driver_features(dev_priv, bdb);
 	parse_edp(dev_priv, bdb);
 
-	pci_unmap_rom(pdev, bios);
+	if (bios)
+		pci_unmap_rom(pdev, bios);
 
 	return 0;
 }