This is a note to let you know that I've just added the patch titled drm/i915/dp: Link train Fallback on eDP only if fallback link BW can fit panel's native mode to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-dp-link-train-fallback-on-edp-only-if-fallback-link-bw-can-fit-panel-s-native-mode.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 041444458835d7fb2c9f042598bfe16bf375b15d Mon Sep 17 00:00:00 2001 From: Manasi Navare <manasi.d.navare@xxxxxxxxx> Date: Tue, 9 Oct 2018 14:28:04 -0700 Subject: drm/i915/dp: Link train Fallback on eDP only if fallback link BW can fit panel's native mode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Manasi Navare <manasi.d.navare@xxxxxxxxx> commit 041444458835d7fb2c9f042598bfe16bf375b15d upstream. This patch fixes the original commit c0cfb10d9e1de49 ("drm/i915/edp: Do not do link training fallback or prune modes on EDP") that causes a blank screen in case of certain eDP panels (Eg: seen on Dell XPS13 9350) where first link training fails and a retraining is required by falling back to lower link rate/lane count. In case of some panels they advertise higher link rate/lane count than whats required for supporting the panel's native mode. But we always link train at highest link rate/lane count for eDP and if that fails we can still fallback to lower link rate/lane count as long as the fallback link BW still fits the native mode to avoid pruning the panel's native mode yet retraining at fallback values to recover from a blank screen. v3: * Add const for fixed_mode (Ville) v2: * Send uevent if link failure on eDP unconditionally Fixes: c0cfb10d9e1d ("drm/i915/edp: Do not do link training fallback or prune modes on EDP") Cc: Clinton Taylor <clinton.a.taylor@xxxxxxxxx> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> # v4.17+ Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107489 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105338 Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx> Tested-by: Alexander Wilson <alexander.wilson@xxxxxxx> Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20181009212804.702-1-manasi.d.navare@xxxxxxxxx (cherry picked from commit 1e712535c51ab025ebc776d4405683d81521996d) Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/intel_dp.c | 30 ++++++++++++++++++++++++++ drivers/gpu/drm/i915/intel_dp_link_training.c | 26 +++++++--------------- 2 files changed, 39 insertions(+), 17 deletions(-) --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -401,6 +401,22 @@ static bool intel_dp_link_params_valid(s return true; } +static bool intel_dp_can_link_train_fallback_for_edp(struct intel_dp *intel_dp, + int link_rate, + uint8_t lane_count) +{ + const struct drm_display_mode *fixed_mode = + intel_dp->attached_connector->panel.fixed_mode; + int mode_rate, max_rate; + + mode_rate = intel_dp_link_required(fixed_mode->clock, 18); + max_rate = intel_dp_max_data_rate(link_rate, lane_count); + if (mode_rate > max_rate) + return false; + + return true; +} + int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp, int link_rate, uint8_t lane_count) { @@ -410,9 +426,23 @@ int intel_dp_get_link_train_fallback_val intel_dp->num_common_rates, link_rate); if (index > 0) { + if (intel_dp_is_edp(intel_dp) && + !intel_dp_can_link_train_fallback_for_edp(intel_dp, + intel_dp->common_rates[index - 1], + lane_count)) { + DRM_DEBUG_KMS("Retrying Link training for eDP with same parameters\n"); + return 0; + } intel_dp->max_link_rate = intel_dp->common_rates[index - 1]; intel_dp->max_link_lane_count = lane_count; } else if (lane_count > 1) { + if (intel_dp_is_edp(intel_dp) && + !intel_dp_can_link_train_fallback_for_edp(intel_dp, + intel_dp_max_common_rate(intel_dp), + lane_count >> 1)) { + DRM_DEBUG_KMS("Retrying Link training for eDP with same parameters\n"); + return 0; + } intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp); intel_dp->max_link_lane_count = lane_count >> 1; } else { --- a/drivers/gpu/drm/i915/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c @@ -352,22 +352,14 @@ intel_dp_start_link_train(struct intel_d return; failure_handling: - /* Dont fallback and prune modes if its eDP */ - if (!intel_dp_is_edp(intel_dp)) { - DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d", - intel_connector->base.base.id, - intel_connector->base.name, - intel_dp->link_rate, intel_dp->lane_count); - if (!intel_dp_get_link_train_fallback_values(intel_dp, - intel_dp->link_rate, - intel_dp->lane_count)) - /* Schedule a Hotplug Uevent to userspace to start modeset */ - schedule_work(&intel_connector->modeset_retry_work); - } else { - DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d", - intel_connector->base.base.id, - intel_connector->base.name, - intel_dp->link_rate, intel_dp->lane_count); - } + DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d", + intel_connector->base.base.id, + intel_connector->base.name, + intel_dp->link_rate, intel_dp->lane_count); + if (!intel_dp_get_link_train_fallback_values(intel_dp, + intel_dp->link_rate, + intel_dp->lane_count)) + /* Schedule a Hotplug Uevent to userspace to start modeset */ + schedule_work(&intel_connector->modeset_retry_work); return; } Patches currently in stable-queue which might be from manasi.d.navare@xxxxxxxxx are queue-4.19/drm-i915-dp-link-train-fallback-on-edp-only-if-fallback-link-bw-can-fit-panel-s-native-mode.patch queue-4.19/drm-i915-icl-fix-the-macros-for-dflexdpmle-register-bits.patch