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>

drivers/gpu/drm/i915/i915_drv.h

@@ -406,6 +406,8 @@ typedef struct drm_i915_private {
 	unsigned int lvds_use_ssc:1;
 	unsigned int display_clock_mode:1;
 	int lvds_ssc_freq;
+	unsigned int bios_lvds_val; /* initial [PCH_]LVDS reg val in VBIOS */
+	unsigned int lvds_val; /* used for checking LVDS channel mode */
 	struct {
 		int rate;
 		int lanes;

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 */

drivers/gpu/drm/i915/intel_display.c

@@ -360,6 +360,27 @@ static const intel_limit_t intel_limits_ironlake_display_port = {
 	.find_pll = intel_find_pll_ironlake_dp,
 };
 
+static bool is_dual_link_lvds(struct drm_i915_private *dev_priv,
+			      unsigned int reg)
+{
+	unsigned int val;
+
+	if (dev_priv->lvds_val)
+		val = dev_priv->lvds_val;
+	else {
+		/* BIOS should set the proper LVDS register value at boot, but
+		 * in reality, it doesn't set the value when the lid is closed;
+		 * we need to check "the value to be set" in VBT when LVDS
+		 * register is uninitialized.
+		 */
+		val = I915_READ(reg);
+		if (!(val & ~LVDS_DETECTED))
+			val = dev_priv->bios_lvds_val;
+		dev_priv->lvds_val = val;
+	}
+	return (val & LVDS_CLKB_POWER_MASK) == LVDS_CLKB_POWER_UP;
+}
+
 static const intel_limit_t *intel_ironlake_limit(struct drm_crtc *crtc,
 						int refclk)
 {
@@ -368,8 +389,7 @@ static const intel_limit_t *intel_ironlake_limit(struct drm_crtc *crtc,
 	const intel_limit_t *limit;
 
 	if (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS)) {
-		if ((I915_READ(PCH_LVDS) & LVDS_CLKB_POWER_MASK) ==
-		    LVDS_CLKB_POWER_UP) {
+		if (is_dual_link_lvds(dev_priv, PCH_LVDS)) {
 			/* LVDS dual channel */
 			if (refclk == 100000)
 				limit = &intel_limits_ironlake_dual_lvds_100m;
@@ -397,8 +417,7 @@ static const intel_limit_t *intel_g4x_limit(struct drm_crtc *crtc)
 	const intel_limit_t *limit;
 
 	if (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS)) {
-		if ((I915_READ(LVDS) & LVDS_CLKB_POWER_MASK) ==
-		    LVDS_CLKB_POWER_UP)
+		if (is_dual_link_lvds(dev_priv, LVDS))
 			/* LVDS with dual channel */
 			limit = &intel_limits_g4x_dual_channel_lvds;
 		else
@@ -536,8 +555,7 @@ intel_find_best_PLL(const intel_limit_t *limit, struct drm_crtc *crtc,
 		 * reliably set up different single/dual channel state, if we
 		 * even can.
 		 */
-		if ((I915_READ(LVDS) & LVDS_CLKB_POWER_MASK) ==
-		    LVDS_CLKB_POWER_UP)
+		if (is_dual_link_lvds(dev_priv, LVDS))
 			clock.p2 = limit->p2.p2_fast;
 		else
 			clock.p2 = limit->p2.p2_slow;