From f4cdbc21444a45d207a8dc175f44d2facfbd0845 Mon Sep 17 00:00:00 2001 From: Jani Nikula Date: Wed, 14 May 2014 13:02:19 +0300 Subject: [PATCH] drm/i915/dp: force eDP lane count to max available lanes on BDW There are certain BDW high res eDP machines that regressed due to commit 38aecea0ccbb909d635619cba22f1891e589b434 Author: Daniel Vetter Date: Mon Mar 3 11:18:10 2014 +0100 drm/i915: reverse dp link param selection, prefer fast over wide again The commit lead to 2 lanes at 5.4 Gbps being used instead of 4 lanes at 2.7 Gbps on the affected machines. Link training succeeded for both, but the screen remained blank with the former config. Further investigation showed that 4 lanes at 5.4 Gbps worked also. The root cause for the blank screen using 2 lanes remains unknown, but apparently the driver for a certain other operating system by default uses the max available lanes. Follow suit on Broadwell eDP, for at least until we figure out what is going on. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76711 Reviewed-by: Daniel Vetter Reviewed-by: Rodrigo Vivi Tested-by: Rodrigo Vivi Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/intel_dp.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 8233f2a..2a00cb8 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -810,7 +810,12 @@ intel_dp_compute_config(struct intel_encoder *encoder, bpp = dev_priv->vbt.edp_bpp; } - if (dev_priv->vbt.edp_lanes) { + if (IS_BROADWELL(dev)) { + /* Yes, it's an ugly hack. */ + min_lane_count = max_lane_count; + DRM_DEBUG_KMS("forcing lane count to max (%u) on BDW\n", + min_lane_count); + } else if (dev_priv->vbt.edp_lanes) { min_lane_count = min(dev_priv->vbt.edp_lanes, max_lane_count); DRM_DEBUG_KMS("using min %u lanes per VBT\n", -- 2.7.4