On Fri, 2016-10-21 at 16:45 -0700, Manasi Navare 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 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.
>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_ddi.c | 15 +++++-
> drivers/gpu/drm/i915/intel_dp.c | 69 ++++++++++++++++++++++++++-
> drivers/gpu/drm/i915/intel_dp_link_training.c | 12 +++--
> drivers/gpu/drm/i915/intel_drv.h | 6 ++-
> 4 files changed, 95 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index fb18d69..451433b 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1712,6 +1712,8 @@ 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);
> @@ -1722,7 +1724,18 @@ 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_ERROR("Link Training failed at link rate = %d, lane count = %d\n",
> + link_rate, lane_count);
> + intel_dp->link_train_failed = true;
> + intel_dp->link_train_failed_link_rate = link_rate;
> + intel_dp->link_train_failed_lane_count = lane_count;
> + /* Schedule a Hotplug Uevent to userspace to start modeset */
> + schedule_work(&connector->i915_modeset_retry_work);
> + } else {
> + intel_dp->link_train_failed = false;
> + }
> +
> 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 c192e18..5d5f4a7 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -313,6 +313,7 @@ static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
> int target_clock = mode->clock;
> int max_rate, mode_rate, max_lanes, max_link_clock;
> int max_dotclk;
> + int common_rates[DP_MAX_SUPPORTED_RATES] = {};
>
> max_dotclk = intel_dp_downstream_max_dotclock(intel_dp);
>
> @@ -326,8 +327,27 @@ static int intel_dp_link_rate_index(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 based on the link rate that failed */
> + if (intel_dp->link_train_failed_link_rate) {
Shouldn't the bool link_train_failed that you are adding be used here?
The naming indicates a check like this should use that.
> + intel_dp->link_rate_index = intel_dp_link_rate_index(intel_dp,
> + common_rates,
> + intel_dp->link_train_failed_link_rate);
> + if (intel_dp->link_rate_index > 0) {
> + max_link_clock = common_rates[intel_dp->link_rate_index - 1];
> + max_lanes = intel_dp_max_lane_count(intel_dp);
> + } else {
> + /* Here we can lower the lane count, but that will be
> + * added for DP Spec 1.3
> + */
> + DRM_ERROR("No Valid Mode Supported for this Link\n");
> + intel_dp->link_train_failed_link_rate = 0;
> + intel_dp->link_rate_index = -1;
> + intel_dp->link_train_failed = false;
1. You are not setting max_link_clock and max_lanes here. Won't this end
up computing the max_rate based on uninitialized locals?
2. Also, what is the correct return value in this case?
3. You are resetting all values when a link rate cannot be found, what
link rate is the subsequent modeset expected to start from?
-DK
> + }
> + } 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);
> @@ -1619,6 +1639,14 @@ 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 (intel_dp->link_train_failed_link_rate) {
> + min_lane_count = max_lane_count;
> + min_clock = max_clock = intel_dp->link_rate_index - 1;
1. Why is min_clock same as max_clock? This forces the clock to a value
instead of iterating it based on the mode rate.
2. Why is min_lane_count set to max_lane_count? Is this done to be Spec
compliant?
3. What about bpp? Looks like the we will still be iterating over bpp to
find the link rate.
-DK
> + intel_dp->link_train_failed_link_rate = 0;
> + intel_dp->link_rate_index = -1;
> + }
> +
> 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],
> @@ -5689,6 +5717,39 @@ 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 drm_connector *connector;
> + struct intel_dp *intel_dp;
> + struct drm_display_mode *mode;
> + bool verbose_prune = true;
> + bool reprobe = false;
> +
> + connector = container_of(work, typeof(*connector),
> + i915_modeset_retry_work);
> + intel_dp = intel_attached_dp(connector);
> +
> + /* 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);
> + mutex_unlock(&connector->dev->mode_config.mutex);
> + if (reprobe) {
> + /* Send Hotplug uevent so userspace can reprobe */
> + drm_kms_helper_hotplug_event(connector->dev);
> + }
> + if (intel_dp->link_train_failed)
> + drm_atomic_helper_connector_modeset(connector);
> +}
> +
> bool
> intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> struct intel_connector *intel_connector)
> @@ -5701,6 +5762,10 @@ 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(&connector->i915_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 4e90b07..d3fcffc 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -890,6 +890,10 @@ struct intel_dp {
> uint32_t DP;
> int link_rate;
> uint8_t lane_count;
> + int link_train_failed_link_rate;
> + uint8_t link_train_failed_lane_count;
> + int link_rate_index;
> + bool link_train_failed;
> uint8_t sink_count;
> bool link_mst;
> bool has_audio;
> @@ -1394,7 +1398,7 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
> void intel_dp_set_link_params(struct intel_dp *intel_dp,
> int link_rate, uint8_t lane_count,
> bool link_mst);
> -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);
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