drm/i915: Use a dmi quirk to skip a broken SDVO TV output.

This IBM system has a multi-function SDVO card that reports both VGA
and TV, but the system has no TV connector.  The TV connector always
reported as connected, which would lead to poor modesetting choices.

https://bugs.freedesktop.org/show_bug.cgi?id=25787

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Tested-by: Vance <liangghv@sg.ibm.com>
Cc: stable@kernel.org
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_sdvo.c

@@ -35,6 +35,7 @@
 #include "i915_drm.h"
 #include "i915_drv.h"
 #include "intel_sdvo_regs.h"
+#include <linux/dmi.h>
 
 static char *tv_format_names[] = {
 	"NTSC_M"   , "NTSC_J"  , "NTSC_443",
@@ -2283,6 +2284,25 @@ intel_sdvo_get_slave_addr(struct drm_device *dev, int output_device)
 		return 0x72;
 }
 
+static int intel_sdvo_bad_tv_callback(const struct dmi_system_id *id)
+{
+	DRM_DEBUG_KMS("Ignoring bad SDVO TV connector for %s\n", id->ident);
+	return 1;
+}
+
+static struct dmi_system_id intel_sdvo_bad_tv[] = {
+	{
+		.callback = intel_sdvo_bad_tv_callback,
+		.ident = "IntelG45/ICH10R/DME1737",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "IBM CORPORATION"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "4800784"),
+		},
+	},
+
+	{ }	/* terminating entry */
+};
+
 static bool
 intel_sdvo_output_setup(struct intel_output *intel_output, uint16_t flags)
 {
@@ -2323,7 +2343,8 @@ intel_sdvo_output_setup(struct intel_output *intel_output, uint16_t flags)
 					(1 << INTEL_SDVO_NON_TV_CLONE_BIT) |
 					(1 << INTEL_ANALOG_CLONE_BIT);
 		}
-	} else if (flags & SDVO_OUTPUT_SVID0) {
+	} else if ((flags & SDVO_OUTPUT_SVID0) &&
+		   !dmi_check_system(intel_sdvo_bad_tv)) {
 
 		sdvo_priv->controlled_output = SDVO_OUTPUT_SVID0;
 		encoder->encoder_type = DRM_MODE_ENCODER_TVDAC;