[Intel-gfx] [PATCH v2 1/4] drm/i915/dp: Link train Fallback on eDP only if fallback link BW can fit panel's native mode
Ville Syrjälä
ville.syrjala at linux.intel.com
Mon Oct 1 16:03:52 UTC 2018
On Wed, Sep 12, 2018 at 03:57:16PM -0700, Manasi Navare wrote:
> 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.
>
> v2:
> * Send uevent if link failure on eDP unconditionally
>
> Cc: Clinton Taylor <clinton.a.taylor at intel.com>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> 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 at intel.com>
> Tested-by: Alexander Wilson <alexander.wilson at ncf.edu>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 29 +++++++++++++++++++
> drivers/gpu/drm/i915/intel_dp_link_training.c | 26 ++++++-----------
> 2 files changed, 38 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 436c22de33b6..e4de5257cd87 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -557,6 +557,21 @@ static bool intel_dp_link_params_valid(struct intel_dp *intel_dp, int link_rate,
> return true;
> }
>
> +static bool intel_dp_can_link_train_fallback_for_edp(struct intel_dp *intel_dp,
> + int link_rate,
> + uint8_t lane_count)
> +{
> + struct drm_display_mode *fixed_mode = intel_dp->attached_connector->panel.fixed_mode;
const
> + 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;
I wonder if we should extract this into a helper and share with
mode_valid(). Then again, it's just a few lines so maybe not worth it.
> +
> + return true;
> +}
> +
> int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> int link_rate, uint8_t lane_count)
> {
> @@ -566,9 +581,23 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> 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;
This whole thing is getting a bit messy. I think it would worthwile to
rewrite this as something like:
intel_dp_update_link_train_fallback_values(intel_dp)
{
int link_rate = intel_dp->link_rate;
int lane_count = intel_dp->lane_count;
if (intel_dp_get_link_train_fallback_values(intel_dp, &link_rate, &lane_count))
return -1;
if (is_edp() && !edp_can_link_train_thing(link_rate, lane_count)) {
DRM_DEBUG_KMS("...");
return 0;
}
intel_dp->max_link_rate = link_rate;
intel_dp->max_link_lane_count = lane_count;
return 0;
}
But that can be done later. With the missing const added this patch is
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> } else {
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index a9f40985a621..30be0e39bd5f 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -367,22 +367,14 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
> 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;
> }
> --
> 2.18.0
--
Ville Syrjälä
Intel
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