On Wed, 11 Feb 2015, Mika Kahola <mika.kahola@xxxxxxxxx> wrote:
> Reuse existing DP link training values i.e. voltage swing
> and pre-emphasis levels, if DP port that we are connected
> to hasn't changed. If we are unable to re-initialize DP
> link, the fallback is to reset the link training values,
> and restart.
Sorry, I failed to remind you to sign your work:
Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
see Documentation/SubmittingPatches for details.
BR,
Jani.
> modified: intel_dp.c
> modified: intel_drv.h
> ---
> drivers/gpu/drm/i915/intel_dp.c | 75 +++++++++++++++++++++++++++++++++++-----
> drivers/gpu/drm/i915/intel_drv.h | 2 ++
> 2 files changed, 69 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 868a07b..c40d64a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3286,6 +3286,25 @@ intel_dp_reset_link_train(struct intel_dp *intel_dp, uint32_t *DP,
> }
>
> static bool
> +intel_dp_reuse_link_train(struct intel_dp *intel_dp, uint32_t *DP,
> + uint8_t dp_train_pat)
> +{
> + struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> + struct drm_device *dev = intel_dig_port->base.base.dev;
> + struct drm_i915_private *dev_priv = dev->dev_private;
> +
> + intel_dp_set_signal_levels(intel_dp, DP);
> +
> + I915_WRITE(intel_dp->output_reg, *DP);
> + POSTING_READ(intel_dp->output_reg);
> +
> + drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_LANE0_SET,
> + intel_dp->train_set, intel_dp->lane_count);
> +
> + return intel_dp_set_link_train(intel_dp, DP, dp_train_pat);
> +}
> +
> +static bool
> intel_dp_update_link_train(struct intel_dp *intel_dp, uint32_t *DP,
> const uint8_t link_status[DP_LINK_STATUS_SIZE])
> {
> @@ -3348,6 +3367,8 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
> int voltage_tries, loop_tries;
> uint32_t DP = intel_dp->DP;
> uint8_t link_config[2];
> + uint8_t link_status[DP_LINK_STATUS_SIZE];
> + bool reuse_train_set = false;
>
> if (HAS_DDI(dev))
> intel_ddi_prepare_link_retrain(encoder);
> @@ -3365,20 +3386,36 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
>
> DP |= DP_PORT_EN;
>
> - /* clock recovery */
> - if (!intel_dp_reset_link_train(intel_dp, &DP,
> - DP_TRAINING_PATTERN_1 |
> - DP_LINK_SCRAMBLING_DISABLE)) {
> - DRM_ERROR("failed to enable link training\n");
> - return;
> + /*
> + * check if DP connector has changed. Reset voltage swing and
> + * pre-emphasis levels if that's the case.
> + */
> + if (intel_dp->connector_changed) {
> + /* reset link training values */
> + DRM_DEBUG_KMS("resetting link train set\n");
> + if (!intel_dp_reset_link_train(intel_dp, &DP,
> + DP_TRAINING_PATTERN_1 |
> + DP_LINK_SCRAMBLING_DISABLE)) {
> + DRM_ERROR("failed to enable link training\n");
> + return;
> + }
> + reuse_train_set = false;
> + }
> + else {
> + DRM_DEBUG_KMS("reusing current link train set\n");
> + if (!intel_dp_reuse_link_train(intel_dp, &DP,
> + DP_TRAINING_PATTERN_1 |
> + DP_LINK_SCRAMBLING_DISABLE)) {
> + DRM_DEBUG_KMS("unable to set known link training values\n");
> + return;
> + }
> + reuse_train_set = true;
> }
>
> voltage = 0xff;
> voltage_tries = 0;
> loop_tries = 0;
> for (;;) {
> - uint8_t link_status[DP_LINK_STATUS_SIZE];
> -
> drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
> if (!intel_dp_get_link_status(intel_dp, link_status)) {
> DRM_ERROR("failed to get link status\n");
> @@ -3389,6 +3426,20 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
> DRM_DEBUG_KMS("clock recovery OK\n");
> break;
> }
> + /*
> + * if we used previously trained voltage and pre-emphasis values
> + * and we don't get clock recovery, reset link training values
> + */
> + if (reuse_train_set) {
> + DRM_DEBUG_KMS("clock recovery not ok, resetting DP train set\n");
> + if (!intel_dp_reset_link_train(intel_dp, &DP,
> + DP_TRAINING_PATTERN_1 |
> + DP_LINK_SCRAMBLING_DISABLE)) {
> + DRM_ERROR("failed to enable link training\n");
> + return;
> + }
> + reuse_train_set = false;
> + }
>
> /* Check to see if we've tried the max voltage */
> for (i = 0; i < intel_dp->lane_count; i++)
> @@ -4076,6 +4127,14 @@ intel_dp_detect(struct drm_connector *connector, bool force)
> connector->base.id, connector->name);
> intel_dp_unset_edid(intel_dp);
>
> + if (connector->base.id != intel_dp->connector_id) {
> + intel_dp->connector_id = connector->base.id;
> + DRM_DEBUG_KMS("DP connector changed\n");
> + intel_dp->connector_changed = true;
> + }
> + else
> + intel_dp->connector_changed = false;
> +
> if (intel_dp->is_mst) {
> /* MST devices are disconnected from a monitor POV */
> if (intel_encoder->type != INTEL_OUTPUT_EDP)
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 1de8e20..2877226 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -648,6 +648,8 @@ struct intel_dp {
> bool has_aux_irq,
> int send_bytes,
> uint32_t aux_clock_divider);
> + uint32_t connector_id;
> + bool connector_changed;
> };
>
> struct intel_digital_port {
> --
> 1.9.1
>
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--
Jani Nikula, Intel Open Source Technology Center
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