drm/i915: Check VBIOS value for determining LVDS dual channel mode, too

Currently i915 driver checks [PCH_]LVDS register bits to decide
whether to set up the dual-link or the single-link mode.  This relies
implicitly on that BIOS initializes the register properly at boot.
However, BIOS doesn't initialize it always.  When the machine is
booted with the closed lid, BIOS skips the LVDS reg initialization.
This ends up in blank output on a machine with a dual-link LVDS when
you open the lid after the boot.

This patch adds a workaround for that problem by checking the initial
LVDS register value in VBT.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=37742
Tested-By: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 0ae76d6b6ea..e4317da848d 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -173,6 +173,28 @@ get_lvds_dvo_timing(const struct bdb_lvds_lfp_data *lvds_lfp_data,
 	return (struct lvds_dvo_timing *)(entry + dvo_timing_offset);
 }
 
+/* get lvds_fp_timing entry
+ * this function may return NULL if the corresponding entry is invalid
+ */
+static const struct lvds_fp_timing *
+get_lvds_fp_timing(const struct bdb_header *bdb,
+		   const struct bdb_lvds_lfp_data *data,
+		   const struct bdb_lvds_lfp_data_ptrs *ptrs,
+		   int index)
+{
+	size_t data_ofs = (const u8 *)data - (const u8 *)bdb;
+	u16 data_size = ((const u16 *)data)[-1]; /* stored in header */
+	size_t ofs;
+
+	if (index >= ARRAY_SIZE(ptrs->ptr))
+		return NULL;
+	ofs = ptrs->ptr[index].fp_timing_offset;
+	if (ofs < data_ofs ||
+	    ofs + sizeof(struct lvds_fp_timing) > data_ofs + data_size)
+		return NULL;
+	return (const struct lvds_fp_timing *)((const u8 *)bdb + ofs);
+}
+
 /* Try to find integrated panel data */
 static void
 parse_lfp_panel_data(struct drm_i915_private *dev_priv,
@@ -182,6 +204,7 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
 	const struct bdb_lvds_lfp_data *lvds_lfp_data;
 	const struct bdb_lvds_lfp_data_ptrs *lvds_lfp_data_ptrs;
 	const struct lvds_dvo_timing *panel_dvo_timing;
+	const struct lvds_fp_timing *fp_timing;
 	struct drm_display_mode *panel_fixed_mode;
 	int i, downclock;
 
@@ -243,6 +266,19 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
 			      "Normal Clock %dKHz, downclock %dKHz\n",
 			      panel_fixed_mode->clock, 10*downclock);
 	}
+
+	fp_timing = get_lvds_fp_timing(bdb, lvds_lfp_data,
+				       lvds_lfp_data_ptrs,
+				       lvds_options->panel_type);
+	if (fp_timing) {
+		/* check the resolution, just to be sure */
+		if (fp_timing->x_res == panel_fixed_mode->hdisplay &&
+		    fp_timing->y_res == panel_fixed_mode->vdisplay) {
+			dev_priv->bios_lvds_val = fp_timing->lvds_reg_val;
+			DRM_DEBUG_KMS("VBT initial LVDS value %x\n",
+				      dev_priv->bios_lvds_val);
+		}
+	}
 }
 
 /* Try to find sdvo panel data */