[PATCH] drm/i915/vlv_dsi: Add DMI quirk for wrong panel modeline in BIOS on Asus TF103C

[Hans de Goede <hdegoede@xxxxxxxxxx>]

Vtotal is wrong in the BIOS supplied modeline for the DSI panel on
the Asus TF103C leading to the last line of the display being shown
as the first line.

The factory installed Android has a hardcoded modeline in its kernel,
causing it to not suffer from this BIOS bug;

and the Android boot-splash which uses the EFI FB which does have this bug
has the last line all black causing the bug to not be visible.

This commit introduces a generic DMI based mechanism for doing modeline
fixups, in case we need similar fixups on other models in the future.

Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
 drivers/gpu/drm/i915/display/vlv_dsi.c | 33 ++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/vlv_dsi.c b/drivers/gpu/drm/i915/display/vlv_dsi.c
index fc0dd0c4079e..98d64b6e132e 100644
--- a/drivers/gpu/drm/i915/display/vlv_dsi.c
+++ b/drivers/gpu/drm/i915/display/vlv_dsi.c
@@ -23,6 +23,7 @@
  * Author: Jani Nikula <jani.nikula@xxxxxxxxx>
  */
 
+#include <linux/dmi.h>
 #include <linux/slab.h>
 
 #include <drm/drm_atomic_helper.h>
@@ -1828,6 +1829,30 @@ static void vlv_dphy_param_init(struct intel_dsi *intel_dsi)
 	intel_dsi_log_params(intel_dsi);
 }
 
+typedef void (*vlv_dsi_mode_fixup_func)(struct drm_display_mode *fixed_mode);
+
+/*
+ * Vtotal is wrong on the Asus TF103C leading to the last line of the display
+ * being shown as the first line. The factory installed Android has a hardcoded
+ * modeline, causing it to not suffer from this BIOS bug.
+ */
+static void vlv_dsi_asus_tf103c_mode_fixup(struct drm_display_mode *fixed_mode)
+{
+	fixed_mode->vtotal = 816;
+	fixed_mode->crtc_vtotal = 816;
+}
+
+static const struct dmi_system_id dmi_mode_fixup_table[] = {
+	{
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "TF103C"),
+		},
+		.driver_data = (void *)vlv_dsi_asus_tf103c_mode_fixup,
+	},
+	{ }
+};
+
 void vlv_dsi_init(struct drm_i915_private *dev_priv)
 {
 	struct drm_device *dev = &dev_priv->drm;
@@ -1837,6 +1862,8 @@ void vlv_dsi_init(struct drm_i915_private *dev_priv)
 	struct intel_connector *intel_connector;
 	struct drm_connector *connector;
 	struct drm_display_mode *current_mode, *fixed_mode;
+	const struct dmi_system_id *dmi_id;
+	vlv_dsi_mode_fixup_func mode_fixup;
 	enum port port;
 	enum pipe pipe;
 
@@ -1965,6 +1992,12 @@ void vlv_dsi_init(struct drm_i915_private *dev_priv)
 		goto err_cleanup_connector;
 	}
 
+	dmi_id = dmi_first_match(dmi_mode_fixup_table);
+	if (dmi_id) {
+		mode_fixup = (vlv_dsi_mode_fixup_func)dmi_id->driver_data;
+		mode_fixup(fixed_mode);
+	}
+
 	intel_panel_init(&intel_connector->panel, fixed_mode, NULL);
 	intel_backlight_setup(intel_connector, INVALID_PIPE);
 
-- 
2.33.1