Commit 6f317cfe authored Apr 12, 2015 by Lukas Wunner Committed by Jani Nikula May 05, 2015

drm/i915: Assume dual channel LVDS if pixel clock necessitates it

Single channel LVDS maxes out at 112 MHz, anything above must be dual
channel. This avoids the need to specify i915.lvds_channel_mode=2 on
all 17" MacBook Pro models with i915 graphics since they had 1920x1200
(193 MHz), plus those 15" pre-retina models which had a resolution
of 1680x1050 (119 MHz) as a BTO option.

Source for 112 MHz limit of single channel LVDS is section 2.3 of:
https://01.org/linuxgraphics/sites/default/files/documentation/ivb_ihd_os_vol3_part4.pdf



v2: Avoid hardcoding 17" models by assuming dual channel LVDS if the
resolution necessitates it, suggested by Jani Nikula.

v3: Fix typo, thanks Joonas Lahtinen.

v4: Split commit in two, suggested by Ville Syrjälä.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
[Jani: included spec reference into the commit message]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

parent 5ebe6afa

drivers/gpu/drm/i915/intel_lvds.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -848,6 +848,11 @@ static bool compute_is_dual_link_lvds(struct intel_lvds_encoder *lvds_encoder)
		if (i915.lvds_channel_mode > 0)
		return i915.lvds_channel_mode == 2;

		/* single channel LVDS is limited to 112 MHz */
		if (lvds_encoder->attached_connector->base.panel.fixed_mode->clock
		> 112999)
		return true;

		if (dmi_check_system(intel_dual_link_lvds))
		return true;

		@@ -1111,6 +1116,8 @@ void intel_lvds_init(struct drm_device *dev)
		out:
		mutex_unlock(&dev->mode_config.mutex);

		intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);

		lvds_encoder->is_dual_link = compute_is_dual_link_lvds(lvds_encoder);
		DRM_DEBUG_KMS("detected %s-link lvds configuration\n",
		lvds_encoder->is_dual_link ? "dual" : "single");
		@@ -1125,7 +1132,6 @@ void intel_lvds_init(struct drm_device *dev)
		}
		drm_connector_register(connector);

		intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);
		intel_panel_setup_backlight(connector, INVALID_PIPE);

		return;