[Intel-gfx] [PATCH v2 4/4] drm/i915: Implement Link Rate fallback on Link training failure
Jani Nikula
jani.nikula at linux.intel.com
Tue Nov 1 08:49:14 UTC 2016
On Sat, 29 Oct 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.
>
> v2:
> * Squashed a few patches (Jani Nikula)
>
> 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/drm_atomic_helper.c | 4 ++
> drivers/gpu/drm/i915/intel_ddi.c | 23 ++++++++-
> drivers/gpu/drm/i915/intel_dp.c | 74 +++++++++++++++++++++++++--
> drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
> drivers/gpu/drm/i915/intel_drv.h | 5 +-
> 5 files changed, 110 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 75ad01d..a3df3a4 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -519,6 +519,10 @@ static int handle_conflicting_encoders(struct drm_atomic_state *state,
> connector_state);
> if (ret)
> return ret;
> +
> + crtc_state = drm_atomic_get_existing_crtc_state(state, connector->state->crtc);
> + if (connector->link_status == DRM_MODE_LINK_STATUS_BAD)
> + crtc_state->connectors_changed = true;
> }
>
> /*
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 938ac4d..319eeca 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1684,6 +1684,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> enum port port = intel_ddi_get_encoder_port(encoder);
> + struct intel_connector *intel_connector = intel_dp->attached_connector;
> + struct drm_connector *connector = &intel_connector->base;
>
> intel_dp_set_link_params(intel_dp, link_rate, lane_count,
> link_mst);
> @@ -1694,7 +1696,26 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
> intel_prepare_dp_ddi_buffers(encoder);
> intel_ddi_init_dp_buf_reg(encoder);
> intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> - intel_dp_start_link_train(intel_dp);
> + if (!intel_dp_start_link_train(intel_dp)) {
> + DRM_DEBUG_KMS("Link Training failed at link rate = %d, lane count = %d",
> + link_rate, lane_count);
> + intel_dp->link_train_failed = true;
> + intel_dp_get_link_train_fallback_values(intel_dp, link_rate,
> + lane_count);
> + /* Schedule a Hotplug Uevent to userspace to start modeset */
> + schedule_work(&intel_connector->modeset_retry_work);
This is not just about DDI. Need to do this for the other cases too.
> + } else {
> + DRM_DEBUG_KMS("Link Training Passed at Link Rate = %d, Lane count = %d",
> + link_rate, lane_count);
> + intel_dp->link_train_failed = false;
> + intel_dp->fallback_link_rate_index = -1;
> + intel_dp->fallback_link_rate = 0;
> + intel_dp->fallback_lane_count = 0;
> + connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> + intel_dp_set_link_status_property(connector,
> + DRM_MODE_LINK_STATUS_GOOD);
Looks like you never actually read connector->link_status... Why do you
need both connector->link_status and intel_dp->link_train_failed? Do you
think you have 4 states? What are they? Can't this all be in sync with
the property?
> + }
> +
> if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
> intel_dp_stop_link_train(intel_dp);
> }
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index fb4fcdd..d1f0e2c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -354,8 +354,14 @@ void 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 (intel_dp->link_train_failed) {
> + 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);
> @@ -1640,6 +1646,12 @@ 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 (intel_dp->link_train_failed) {
> + min_lane_count = max_lane_count = intel_dp->fallback_lane_count;
> + min_clock = max_clock = intel_dp->fallback_link_rate_index;
> + }
> +
My general feeling is that there's starting to be a bit too much special
casing around the fallback values. I'm not decided we need to fix this
right away in this series, or whether it can be follow-up work.
One idea is to compute the common rates and lanes once when they're
first needed, and all of the helpers would use that info. The fallback
code would just trim those, and the conditional fallback stuff could be
removed from all over the place.
> 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],
> @@ -4423,6 +4435,13 @@ 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->link_train_failed = false;
> + intel_dp->fallback_link_rate_index = -1;
> + intel_dp->fallback_link_rate = 0;
> + intel_dp->fallback_lane_count = 0;
> + connector->link_status = DRM_MODE_LINK_STATUS_GOOD;
> + intel_dp_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",
> @@ -4514,8 +4533,12 @@ 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 && intel_dp->link_train_failed)
> + return status;
> +
> /* If full detect is not performed yet, do a full detect */
> - if (!intel_dp->detect_done)
> + if (!intel_dp->detect_done && !intel_dp->link_train_failed)
> status = intel_dp_long_pulse(intel_dp->attached_connector);
>
> intel_dp->detect_done = false;
> @@ -5692,6 +5715,47 @@ 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;
> + bool reprobe = false;
> +
> + 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);
> + if (mode->status != MODE_OK)
> + reprobe = true;
> + }
> + drm_mode_prune_invalid(connector->dev, &connector->modes,
> + verbose_prune);
> +
> + /* Set connector link status to BAD only if modeset required
> + * for the current mode, if mode list changed then just send uevent
> + * so that it can reprobe the connectors and validate modes and do
> + * a modeset on a different valid mode.
> + */
> + if (!reprobe) {
> + connector->link_status = DRM_MODE_LINK_STATUS_BAD;
> + intel_dp_set_link_status_property(connector,
> + DRM_MODE_LINK_STATUS_BAD);
> + }
I think the link status property should be set to bad unconditionally
here. If the current link is bad, it is bad right now independent of
modes fitting into the fallback link parameters.
Which makes me think, unless I'm missing something, that you might be
able to prune the invalid modes and set the property right away when
link training fails, and only use the work to do
drm_kms_helper_hotplug_event.
> + 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)
> @@ -5704,6 +5768,10 @@ 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..10f81ab 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -310,9 +310,15 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp)
> DP_TRAINING_PATTERN_DISABLE);
> }
>
> -void
> +bool
> 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);
> + bool ret;
> +
> + if (intel_dp_link_training_clock_recovery(intel_dp)) {
> + ret = intel_dp_link_training_channel_equalization(intel_dp);
> + if (ret)
> + return true;
> + }
> + return false;
> }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index bc25b2b..a54e9b7 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -312,6 +312,9 @@ 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 {
> @@ -1402,7 +1405,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
> bool link_mst);
> void intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> int link_rate, uint8_t lane_count);
> -void intel_dp_start_link_train(struct intel_dp *intel_dp);
> +bool intel_dp_start_link_train(struct intel_dp *intel_dp);
> void intel_dp_stop_link_train(struct intel_dp *intel_dp);
> void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
> void intel_dp_encoder_reset(struct drm_encoder *encoder);
--
Jani Nikula, Intel Open Source Technology Center
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