[PATCH 5/5] drm/i915: Implement Link Rate fallback on Link training failure
Manasi Navare
manasi.d.navare at intel.com
Fri Nov 18 15:29:51 UTC 2016
On Fri, Nov 18, 2016 at 03:31:48PM +0200, Jani Nikula wrote:
> On Fri, 18 Nov 2016, Manasi Navare <manasi.d.navare at intel.com> wrote:
> > If link training at a link rate optimal for a particular
> > mode fails during modeset's atomic commit phase, then we
> > let the modeset complete and then retry. We save the link rate
> > value at which link training failed, update the link status property
> > to "BAD" and use a lower link rate to prune the modes. It will redo
> > the modeset on the current mode at lower link rate or if the current
> > mode gets pruned due to lower link constraints then, it will send a
> > hotplug uevent for userspace to handle it.
> >
> > This is also required to pass DP CTS tests 4.3.1.3, 4.3.1.4,
> > 4.3.1.6.
> >
> > v7:
> > Remove the redundant variable in previous patch itself
> > v6:
> > * Obtain link rate index from fallback_link_rate using
> > the helper intel_dp_link_rate_index (Jani Nikula)
> > * Include fallback within intel_dp_start_link_train (Jani Nikula)
> > v5:
> > * Move set link status to drm core (Daniel Vetter, Jani Nikula)
> > v4:
> > * Add fallback support for non DDI platforms too
> > * Set connector->link status inside set_link_status function
> > (Jani Nikula)
> > v3:
> > * Set link status property to BAd unconditionally (Jani Nikula)
> > * Dont use two separate variables link_train_failed and link_status
> > to indicate same thing (Jani Nikula)
> > v2:
> > * Squashed a few patches (Jani Nikula)
> >
> > Acked-by: Tony Cheng <tony.cheng at amd.com>
> > Acked-by: Harry Wentland <Harry.wentland at amd.com>
> > Cc: Jani Nikula <jani.nikula at linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter at intel.com>
> > Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 63 ++++++++++++++++++++++++++-
> > drivers/gpu/drm/i915/intel_dp_link_training.c | 28 +++++++++++-
> > drivers/gpu/drm/i915/intel_drv.h | 3 ++
> > 3 files changed, 90 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 4fb89e1..a56a34d 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -351,8 +351,14 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> > target_clock = fixed_mode->clock;
> > }
> >
> > - max_link_clock = intel_dp_max_link_rate(intel_dp);
> > - max_lanes = intel_dp_max_lane_count(intel_dp);
> > + /* Prune the modes using the fallback link rate/lane count */
> > + if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> > + max_link_clock = intel_dp->fallback_link_rate;
> > + max_lanes = intel_dp->fallback_lane_count;
> > + } else {
> > + max_link_clock = intel_dp_max_link_rate(intel_dp);
> > + max_lanes = intel_dp_max_lane_count(intel_dp);
> > + }
> >
> > max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> > mode_rate = intel_dp_link_required(target_clock, 18);
> > @@ -1588,6 +1594,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> > enum port port = dp_to_dig_port(intel_dp)->port;
> > struct intel_crtc *intel_crtc = to_intel_crtc(pipe_config->base.crtc);
> > struct intel_connector *intel_connector = intel_dp->attached_connector;
> > + struct drm_connector *connector = &intel_connector->base;
> > int lane_count, clock;
> > int min_lane_count = 1;
> > int max_lane_count = intel_dp_max_lane_count(intel_dp);
> > @@ -1635,6 +1642,14 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> > if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
> > return false;
> >
> > + /* Fall back to lower link rate in case of failure in previous modeset */
> > + if (connector->link_status == DRM_MODE_LINK_STATUS_BAD) {
> > + min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> > + min_clock = max_clock = intel_dp_link_rate_index(intel_dp,
> > + common_rates,
> > + intel_dp->fallback_link_rate);
> > + }
> > +
> > DRM_DEBUG_KMS("DP link computation with max lane count %i "
> > "max bw %d pixel clock %iKHz\n",
> > max_lane_count, common_rates[max_clock],
> > @@ -4415,6 +4430,10 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> > intel_dp->compliance_test_active = 0;
> > intel_dp->compliance_test_type = 0;
> > intel_dp->compliance_test_data = 0;
> > + intel_dp->fallback_link_rate = 0;
> > + intel_dp->fallback_lane_count = 0;
> > + drm_mode_connector_set_link_status_property(connector,
> > + DRM_MODE_LINK_STATUS_GOOD);
> >
> > if (intel_dp->is_mst) {
> > DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> > @@ -4506,6 +4525,11 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> > DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> > connector->base.id, connector->name);
> >
> > + /* If this is a retry due to link trianing failure */
> > + if (status == connector_status_connected &&
> > + connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> > + return status;
> > +
> > /* If full detect is not performed yet, do a full detect */
> > if (!intel_dp->detect_done)
> > status = intel_dp_long_pulse(intel_dp->attached_connector);
> > @@ -5671,6 +5695,37 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> > return false;
> > }
> >
> > +static void intel_dp_modeset_retry_work_fn(struct work_struct *work)
> > +{
> > + struct intel_connector *intel_connector;
> > + struct drm_connector *connector;
> > + struct drm_display_mode *mode;
> > + bool verbose_prune = true;
>
> Nitpick, totally unnecessary temporary variable.
>
Ok, then directly use true while calling the drm_prune_invalid function?
> > +
> > + intel_connector = container_of(work, typeof(*intel_connector),
> > + modeset_retry_work);
> > + connector = &intel_connector->base;
> > +
> > + /* Grab the locks before changing connector property*/
> > + mutex_lock(&connector->dev->mode_config.mutex);
> > + DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
> > + connector->name);
> > + list_for_each_entry(mode, &connector->modes, head) {
> > + mode->status = intel_dp_mode_valid(connector,
> > + mode);
> > + }
>
> The first time we end up here, we'll still have "good" link status, and
> the fallback values won't be taken into account in
> intel_dp_mode_valid(). If there are modes that no longer fit into the
> fallback values, compute config will fail off the bat the next time
> around. So I think you should set link status to bad first.
>
> BR,
> Jani.
>
Yes, I totally agree, this property need sto be set first and then call mode valid.
Manasi
> > + drm_mode_prune_invalid(connector->dev, &connector->modes,
> > + verbose_prune);
> > + /* Set connector link status to BAD and send a Uevent to notify
> > + * userspace to do a modeset.
> > + */
> > + drm_mode_connector_set_link_status_property(connector,
> > + DRM_MODE_LINK_STATUS_BAD);
> > + mutex_unlock(&connector->dev->mode_config.mutex);
> > + /* Send Hotplug uevent so userspace can reprobe */
> > + drm_kms_helper_hotplug_event(connector->dev);
> > +}
> > +
> > bool
> > intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> > struct intel_connector *intel_connector)
> > @@ -5683,6 +5738,10 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
> > enum port port = intel_dig_port->port;
> > int type;
> >
> > + /* Initialize the work for modeset in case of link train failure */
> > + INIT_WORK(&intel_connector->modeset_retry_work,
> > + intel_dp_modeset_retry_work_fn);
> > +
> > if (WARN(intel_dig_port->max_lanes < 1,
> > "Not enough lanes (%d) for DP on port %c\n",
> > intel_dig_port->max_lanes, port_name(port)))
> > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > index 0048b52..cc243db 100644
> > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > @@ -313,6 +313,30 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> > void
> > intel_dp_start_link_train(struct intel_dp *intel_dp)
> > {
> > - intel_dp_link_training_clock_recovery(intel_dp);
> > - intel_dp_link_training_channel_equalization(intel_dp);
> > + struct intel_connector *intel_connector = intel_dp->attached_connector;
> > + struct drm_connector *connector = &intel_connector->base;
> > +
> > + if (!intel_dp_link_training_clock_recovery(intel_dp))
> > + goto failure_handling;
> > + if (!intel_dp_link_training_channel_equalization(intel_dp))
> > + goto failure_handling;
> > +
> > + /* Reset the Link Train Values */
> > + DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> > + intel_dp->link_rate, intel_dp->lane_count);
> > + intel_dp->fallback_link_rate = 0;
> > + intel_dp->fallback_lane_count = 0;
> > + drm_mode_connector_set_link_status_property(connector,
> > + DRM_MODE_LINK_STATUS_GOOD);
> > + return;
> > +
> > + failure_handling:
> > + DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> > + 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;
> > }
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index e1c43a9..33be66f 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -315,6 +315,9 @@ struct intel_connector {
> > void *port; /* store this opaque as its illegal to dereference it */
> >
> > struct intel_dp *mst_port;
> > +
> > + /* Work struct to schedule a uevent on link train failure */
> > + struct work_struct modeset_retry_work;
> > };
> >
> > struct dpll {
>
> --
> Jani Nikula, Intel Open Source Technology Center
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