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

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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>
This commit is contained in:
Lukas Wunner 2015-04-12 21:10:35 +02:00 committed by Jani Nikula
parent 5ebe6afaf0
commit 6f317cfe42
1 changed files with 7 additions and 1 deletions
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8
drivers/gpu/drm/i915/intel_lvds.c
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@ -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 @@ out:
}
drm_connector_register(connector);
intel_panel_init(&intel_connector->panel, fixed_mode, downclock_mode);
intel_panel_setup_backlight(connector, INVALID_PIPE);
return;