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>
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 5abda1d..ee621e3 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -848,6 +848,11 @@
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 @@
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 @@
}
drm_connector_register(connector);
- intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);
intel_panel_setup_backlight(connector, INVALID_PIPE);
return;