[PATCH 1/2] drm/i915: Consult VBT "LVDS config" bits to determine whether internal LVDS is present

* [PATCH 1/2] drm/i915: Consult VBT "LVDS config" bits to determine whether internal LVDS is present
@ 2018-05-04 14:13 Ville Syrjala
  2018-05-04 14:13 ` [PATCH 2/2] drm/i915: Eliminate the unused dev_priv->vbt.lvds_vbt Ville Syrjala
                   ` (5 more replies)
  0 siblings, 6 replies; 8+ messages in thread
From: Ville Syrjala @ 2018-05-04 14:13 UTC (permalink / raw)
  To: intel-gfx; +Cc: Jani Nikula, Ondrej Zary

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

VBT seems to have some bits to tell us whether the internal LVDS port
has something hooked up. In theory one might expect the VBT to not have
a child device for the LVDS port if there's no panel hooked up, but
in practice many VBTs still add the child device. The "LVDS config" bits
seem more reliable though, so let's check those.

So far we've used the "LVDS config" bits to check for eDP support on
ILK+, and disable the internal LVDS when the value is 3. That value
is actually documented as "Both internal LVDS and SDVO LVDS", but in
practice it looks to mean "eDP" on all the ilk+ VBTs I've seen. So let's
keep that interpretation, but for pre-ILK we will consider the value
3 to also indicate the presence of the internal LVDS.

Currently we have 25 DMI matches for the "no internal LVDS" quirk. In an
effort to reduce that let's toss in a WARN when the DMI match and VBT
both tell us that the internal LVDS is not present. The hope is that
people will report a bug, and then we can just nuke the corresponding
entry from the DMI quirk list. Credits to Jani for this idea.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ondrej Zary <linux@rainbow-software.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105468
References: https://lists.freedesktop.org/archives/intel-gfx/2018-March/158408.html
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h       |  1 +
 drivers/gpu/drm/i915/intel_bios.c     | 20 ++++++++++++++++++--
 drivers/gpu/drm/i915/intel_lvds.c     | 14 +++++++++-----
 drivers/gpu/drm/i915/intel_vbt_defs.h |  1 +
 4 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 04e27806e581..ffd0c8d33336 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1052,6 +1052,7 @@ struct intel_vbt_data {
 	unsigned int lvds_vbt:1;
 	unsigned int int_crt_support:1;
 	unsigned int lvds_use_ssc:1;
+	unsigned int int_lvds_support:1;
 	unsigned int display_clock_mode:1;
 	unsigned int fdi_rx_polarity_inverted:1;
 	unsigned int panel_type:4;
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 702d3fab97fc..f75541b11f11 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -518,8 +518,21 @@ parse_driver_features(struct drm_i915_private *dev_priv,
 	if (!driver)
 		return;
 
-	if (driver->lvds_config == BDB_DRIVER_FEATURE_EDP)
-		dev_priv->vbt.edp.support = 1;
+	if (INTEL_GEN(dev_priv) >= 5) {
+		if (driver->lvds_config != BDB_DRIVER_FEATURE_INT_LVDS)
+			dev_priv->vbt.int_lvds_support = 0;
+
+		/*
+		 * Note that the VBT spec doesn't agree with this
+		 * interpretation, but real world VBTs seem to.
+		 */
+		if (driver->lvds_config == BDB_DRIVER_FEATURE_EDP)
+			dev_priv->vbt.edp.support = 1;
+	} else {
+		if (driver->lvds_config != BDB_DRIVER_FEATURE_INT_LVDS &&
+		    driver->lvds_config != BDB_DRIVER_FEATURE_INT_SDVO_LVDS)
+			dev_priv->vbt.int_lvds_support = 0;
+	}
 
 	DRM_DEBUG_KMS("DRRS State Enabled:%d\n", driver->drrs_enabled);
 	/*
@@ -1512,6 +1525,9 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
 	dev_priv->vbt.int_tv_support = 1;
 	dev_priv->vbt.int_crt_support = 1;
 
+	/* driver features */
+	dev_priv->vbt.int_lvds_support = 1;
+
 	/* Default to using SSC */
 	dev_priv->vbt.lvds_use_ssc = 1;
 	/*
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index d35d2d50f595..f6596c5ce973 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -962,8 +962,16 @@ void intel_lvds_init(struct drm_i915_private *dev_priv)
 		return;
 
 	/* Skip init on machines we know falsely report LVDS */
-	if (dmi_check_system(intel_no_lvds))
+	if (dmi_check_system(intel_no_lvds)) {
+		WARN(!dev_priv->vbt.int_lvds_support,
+		     "Useless DMI match. Internal LVDS support disabled by VBT\n");
 		return;
+	}
+
+	if (!dev_priv->vbt.int_lvds_support) {
+		DRM_DEBUG_KMS("Internal LVDS support disabled by VBT.\n");
+		return;
+	}
 
 	if (HAS_PCH_SPLIT(dev_priv))
 		lvds_reg = PCH_LVDS;
@@ -975,10 +983,6 @@ void intel_lvds_init(struct drm_i915_private *dev_priv)
 	if (HAS_PCH_SPLIT(dev_priv)) {
 		if ((lvds & LVDS_DETECTED) == 0)
 			return;
-		if (dev_priv->vbt.edp.support) {
-			DRM_DEBUG_KMS("disable LVDS for eDP support\n");
-			return;
-		}
 	}
 
 	pin = GMBUS_PIN_PANEL;
diff --git a/drivers/gpu/drm/i915/intel_vbt_defs.h b/drivers/gpu/drm/i915/intel_vbt_defs.h
index 458468237b5f..a1d5e39f9a00 100644
--- a/drivers/gpu/drm/i915/intel_vbt_defs.h
+++ b/drivers/gpu/drm/i915/intel_vbt_defs.h
@@ -635,6 +635,7 @@ struct bdb_sdvo_lvds_options {
 #define BDB_DRIVER_FEATURE_NO_LVDS		0
 #define BDB_DRIVER_FEATURE_INT_LVDS		1
 #define BDB_DRIVER_FEATURE_SDVO_LVDS		2
+#define BDB_DRIVER_FEATURE_INT_SDVO_LVDS	3
 #define BDB_DRIVER_FEATURE_EDP			3
 
 struct bdb_driver_features {
-- 
2.16.1

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