[PATCH 2/2] drm/i915/lvds: Use i915.lvds_fixed_mode= as a last resort

[Chris Wilson <chris@chris-wilson.co.uk>]

If we can find no other reliable source of panel configuration data,
turn to the user and see if they have a passed a mode line (ala video=)
through the i915.lvds_fixed_mode= string.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Oliver Seitz <info@vtnd.de>
Cc: Mike Isely <isely@isely.net>
Cc: Dave Airlied <airlied@linux.ie>
---
 drivers/gpu/drm/i915/i915_drv.c   |    4 +++
 drivers/gpu/drm/i915/i915_drv.h   |    3 +-
 drivers/gpu/drm/i915/intel_lvds.c |   46 ++++++++++++++++++++++++++++---------
 3 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 16a2532..4a618f6 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -67,6 +67,10 @@ module_param_named(vbt_sdvo_panel_type, i915_vbt_sdvo_panel_type, int, 0600);
 static bool i915_try_reset = true;
 module_param_named(reset, i915_try_reset, bool, 0600);
 
+char *i915_lvds_fixed_mode;
+module_param_named(lvds_fixed_mode, i915_lvds_fixed_mode, charp, 0600);
+MODULE_PARM_DESC(lvds_fixed_mode, "specify the mode line for the LVDS panel to be used in the absence of any configuration data, using the video= format");
+
 unsigned int i915_lvds_24bit = 0;
 module_param_named(lvds_24bit, i915_lvds_24bit, int, 0600);
 MODULE_PARM_DESC(lvds_24bit, "LVDS 24 bit pixel format: 0=leave untouched (default), 1=24 bit '2.0' format, 2=24 bit '2.1' format, 3=force older 18 bit format");
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2112af3..c6cc4e2 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -977,12 +977,13 @@ extern unsigned int i915_fbpercrtc;
 extern int i915_panel_ignore_lid;
 extern unsigned int i915_powersave;
 extern unsigned int i915_semaphores;
+extern char *i915_lvds_fixed_mode;
 extern unsigned int i915_lvds_channels;
+extern unsigned int i915_lvds_24bit;
 extern unsigned int i915_lvds_downclock;
 extern unsigned int i915_panel_use_ssc;
 extern int i915_vbt_sdvo_panel_type;
 extern unsigned int i915_enable_rc6;
-extern unsigned int i915_lvds_24bit;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index a562bd2..32b86ea 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -924,6 +924,11 @@ bool intel_lvds_init(struct drm_device *dev)
 	 *    if none of the above, no panel
 	 * 4) make sure lid is open
 	 *    if closed, act like it's not there for now
+	 *
+	 * Finally, we allow the user to specify his own mode. We do this
+	 * last because we want to prevent the user from damaging their
+	 * hardware with a dangerous modeline. Though we may eventually
+	 * be forced to add an override for truly broken machines.
 	 */
 
 	/*
@@ -982,19 +987,38 @@ bool intel_lvds_init(struct drm_device *dev)
 	 */
 
 	/* Ironlake: FIXME if still fail, not try pipe mode now */
-	if (HAS_PCH_SPLIT(dev))
-		goto failed;
+	if (!HAS_PCH_SPLIT(dev)) {
+		lvds = I915_READ(LVDS);
+		pipe = (lvds & LVDS_PIPEB_SELECT) ? 1 : 0;
+		crtc = intel_get_crtc_for_pipe(dev, pipe);
+
+		if (crtc && (lvds & LVDS_PORT_EN)) {
+			intel_lvds->fixed_mode = intel_crtc_mode_get(dev, crtc);
+			if (intel_lvds->fixed_mode) {
+				intel_lvds->fixed_mode->type |=
+					DRM_MODE_TYPE_PREFERRED;
+				goto out;
+			}
+		}
+	}
 
-	lvds = I915_READ(LVDS);
-	pipe = (lvds & LVDS_PIPEB_SELECT) ? 1 : 0;
-	crtc = intel_get_crtc_for_pipe(dev, pipe);
+	/* No panel cnnfiguration data, and nothing already driving the panel
+	 * at its preferred mode. Check to see if the user provided this vital
+	 * bit of information...
+	 */
+	if (i915_lvds_fixed_mode) {
+		struct drm_cmdline_mode mode;
 
-	if (crtc && (lvds & LVDS_PORT_EN)) {
-		intel_lvds->fixed_mode = intel_crtc_mode_get(dev, crtc);
-		if (intel_lvds->fixed_mode) {
-			intel_lvds->fixed_mode->type |=
-				DRM_MODE_TYPE_PREFERRED;
-			goto out;
+		if (drm_mode_parse_command_line_for_connector(i915_lvds_fixed_mode,
+							      connector,
+							      &mode)) {
+			intel_lvds->fixed_mode =
+				drm_mode_create_from_cmdline_mode(dev, &mode);
+			if (intel_lvds->fixed_mode) {
+				intel_lvds->fixed_mode->type |=
+					DRM_MODE_TYPE_PREFERRED;
+				goto out;
+			}
 		}
 	}
 
-- 
1.7.4.1