drm/i915: Get panel_type from OpRegion panel details

We've had problems on several occasions with using the panel type
from the VBT block 40. Usually it seems to be 2, which often
doesn't give us the correct timings for the panel. After some
more digging I found a way to get a panel type via the OpRegion
SWSCI GBDA "Get Panel Details" method. Let's try to use it.

The spec has this to say about the output:
"Bits [15:8] - Panel Type
 Bits contain the panel type user setting from CMOS
 00h = Not Valid, use default Panel Type & Timings from VBT
 01h - 0Fh = Panel Number"

Another version of the spec lists the valid range as 1-16, which makes
more sense since VBT supports 16 panels. Based on actual results
from Rob's G45, 1-16 is what we need to accept.

The other bits in the output don't look relevant for the problem at
hand.

The input is specified as:
"Bits [31:4] - Reserved
 Reserved (must be zero)
 Bits [3:0] - Panel Number
 These bits contain the sequential index of Panel, starting at 0 and
 counting upwards from the first integrated Internal Flat-Panel Display
 Encoder present, and then from the first external Display Encoder
 (e.g., S/DVO-B then S/DVO-C) which supports Internal Flat-Panels.
 0h - 0Fh = Panel number"

For now I've just hardcoded the input panel number as 0. That would seem
like a decent choise for LVDS. Not so sure about eDP when port != A.

v2: Accept values 1-16
    Filter out bogus results in opregion code (Jani)
    Add debug logging for all the different branches (Jani)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rob Kramer <rob@solution-space.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94825
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460359431-11003-1-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Rob Kramer <rob@solution-space.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -3457,6 +3457,7 @@ extern int intel_opregion_notify_encoder(struct intel_encoder *intel_encoder,
 					 bool enable);
 extern int intel_opregion_notify_adapter(struct drm_device *dev,
 					 pci_power_t state);
+extern int intel_opregion_get_panel_type(struct drm_device *dev);
 #else
 static inline int intel_opregion_setup(struct drm_device *dev) { return 0; }
 static inline void intel_opregion_init(struct drm_device *dev) { return; }
@@ -3472,6 +3473,10 @@ intel_opregion_notify_adapter(struct drm_device *dev, pci_power_t state)
 {
 	return 0;
 }
+static inline int intel_opregion_get_panel_type(struct drm_device *dev)
+{
+	return -ENODEV;
+}
 #endif
 
 /* intel_acpi.c */

drivers/gpu/drm/i915/intel_bios.c

@@ -205,19 +205,29 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
 	struct drm_display_mode *panel_fixed_mode;
 	int panel_type;
 	int drrs_mode;
+	int ret;
 
 	lvds_options = find_section(bdb, BDB_LVDS_OPTIONS);
 	if (!lvds_options)
 		return;
 
 	dev_priv->vbt.lvds_dither = lvds_options->pixel_dither;
-	if (lvds_options->panel_type > 0xf) {
-		DRM_DEBUG_KMS("Invalid VBT panel type 0x%x\n",
-			      lvds_options->panel_type);
-		return;
+
+	ret = intel_opregion_get_panel_type(dev_priv->dev);
+	if (ret >= 0) {
+		WARN_ON(ret > 0xf);
+		panel_type = ret;
+		DRM_DEBUG_KMS("Panel type: %d (OpRegion)\n", panel_type);
+	} else {
+		if (lvds_options->panel_type > 0xf) {
+			DRM_DEBUG_KMS("Invalid VBT panel type 0x%x\n",
+				      lvds_options->panel_type);
+			return;
+		}
+		panel_type = lvds_options->panel_type;
+		DRM_DEBUG_KMS("Panel type: %d (VBT)\n", panel_type);
 	}
 
-	panel_type = lvds_options->panel_type;
 	dev_priv->vbt.panel_type = panel_type;
 
 	drrs_mode = (lvds_options->dps_panel_type_bits

drivers/gpu/drm/i915/intel_opregion.c

@@ -1024,3 +1024,31 @@ int intel_opregion_setup(struct drm_device *dev)
 	memunmap(base);
 	return err;
 }
+
+int
+intel_opregion_get_panel_type(struct drm_device *dev)
+{
+	u32 panel_details;
+	int ret;
+
+	ret = swsci(dev, SWSCI_GBDA_PANEL_DETAILS, 0x0, &panel_details);
+	if (ret) {
+		DRM_DEBUG_KMS("Failed to get panel details from OpRegion (%d)\n",
+			      ret);
+		return ret;
+	}
+
+	ret = (panel_details >> 8) & 0xff;
+	if (ret > 0x10) {
+		DRM_DEBUG_KMS("Invalid OpRegion panel type 0x%x\n", ret);
+		return -EINVAL;
+	}
+
+	/* fall back to VBT panel type? */
+	if (ret == 0x0) {
+		DRM_DEBUG_KMS("No panel type in OpRegion\n");
+		return -ENODEV;
+	}
+
+	return ret - 1;
+}