[PATCH 3.13.y-ckt 047/122] drm/i915: Assume dual channel LVDS if pixel clock necessitates it

From: Kamal Mostafa
Date: Wed Jun 17 2015 - 18:51:28 EST

3.13.11-ckt22 -stable review patch. If anyone has any objections, please let me know.


From: Lukas Wunner <lukas@xxxxxxxxx>

commit 6f317cfe42c9d8a7c9c1a327d2f1bcc517a3cd91 upstream.

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:

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 SyrjÃlÃ.

Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Tested-by: Lukas Wunner <lukas@xxxxxxxxx>
Reviewed-by: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
[Jani: included spec reference into the commit message]
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
[ kamal: backport to 3.13-stable ]
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
drivers/gpu/drm/i915/intel_lvds.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index a837510..0f3a188 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -891,6 +891,11 @@ 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;

@@ -1131,6 +1136,8 @@ void intel_lvds_init(struct drm_device *dev)
goto failed;

+ intel_panel_init(&intel_connector->panel, fixed_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");
@@ -1142,7 +1149,6 @@ out:

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


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