On 11 Dec 2015 7:09 PM, "Durgadoss R" <durgadoss.r@xxxxxxxxx> wrote:
>
> To support USB type C alternate DP mode, the display driver needs to
> know the number of lanes required by the DP panel as well as number
> of lanes that can be supported by the type-C cable. Sometimes, the
> type-C cable may limit the bandwidth even if Panel can support
> more lanes. To address these scenarios, the display driver will
> start link training with max lanes, and if that fails, the driver
> falls back to x2 lanes; and repeats this procedure for all
> bandwidth/lane configurations.
>
> * Since link training is done before modeset only the port
> (and not pipe/planes) and its associated PLLs are enabled.
> * On DP hotplug: Directly start link training on the crtc
> associated with the DP encoder.
> * On Connected boot scenarios: When booted with an LFP and a DP,
> typically, BIOS brings up DP. In these cases, we disable the
> crtc, do upfront link training and then re-enable it back.
> * All local changes made for upfront link training are reset
> to their previous values once it is done; so that the
> subsequent modeset is not aware of these changes.
This is just an aside but do we know if other OSes just always link train at plug time.
I do wonder if we should make an OS level decision to require driver do this always.
Dave.
>
> Signed-off-by: Durgadoss R <durgadoss.r@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_ddi.c | 81 ++++++++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/i915/intel_dp.c | 77 +++++++++++++++++++++++++++++++++++++-
> drivers/gpu/drm/i915/intel_drv.h | 2 +
> 3 files changed, 159 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 632044a..43efc26 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -3274,6 +3274,87 @@ intel_ddi_init_hdmi_connector(struct intel_digital_port *intel_dig_port)
> return connector;
> }
>
> +bool intel_ddi_upfront_link_train(struct intel_dp *intel_dp,
> + struct intel_crtc *crtc)
> +{
> + struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> + struct intel_connector *connector = intel_dp->attached_connector;
> + struct intel_encoder *encoder = connector->encoder;
> + struct drm_device *dev = encoder->base.dev;
> + struct drm_i915_private *dev_priv = dev->dev_private;
> + struct intel_shared_dpll *pll;
> + struct drm_crtc *drm_crtc = NULL;
> + struct intel_crtc_state *tmp_crtc_config;
> + struct intel_dpll_hw_state tmp_dpll_hw_state;
> + uint8_t link_bw, lane_count;
> +
> + if (!crtc) {
> + drm_crtc = intel_get_unused_crtc(&encoder->base);
> + if (!drm_crtc) {
> + DRM_ERROR("No crtc for upfront link training\n");
> + return false;
> + }
> + encoder->base.crtc = drm_crtc;
> + crtc = to_intel_crtc(drm_crtc);
> + }
> +
> + /* Initialize with Max Link rate & lane count supported by panel */
> + link_bw = intel_dp->dpcd[DP_MAX_LINK_RATE];
> + lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> +
> + /* Save the crtc->config */
> + tmp_crtc_config = crtc->config;
> + tmp_dpll_hw_state = crtc->config->dpll_hw_state;
> +
> + /* Select the shared DPLL to use for this port */
> + intel_get_ddi_pll(dev_priv, dig_port->port, crtc->config);
> + pll = intel_crtc_to_shared_dpll(crtc);
> + if (!pll) {
> + DRM_ERROR("Could not get shared DPLL\n");
> + goto exit;
> + }
> + DRM_DEBUG_KMS("Using %s for pipe %c\n", pll->name, pipe_name(crtc->pipe));
> +
> + do {
> + crtc->config->port_clock = drm_dp_bw_code_to_link_rate(link_bw);
> + crtc->config->lane_count = lane_count;
> + if (!intel_ddi_pll_select(crtc, crtc->config, encoder, false))
> + goto exit;
> +
> + pll->config.crtc_mask |= (1 << crtc->pipe);
> + pll->config.hw_state = crtc->config->dpll_hw_state;
> +
> + /* Enable PLL followed by port */
> + intel_enable_shared_dpll(crtc);
> + encoder->pre_enable(encoder);
> +
> + /* Check if link training passed; if so update DPCD */
> + if (intel_dp->train_set_valid)
> + intel_dp_update_dpcd_params(intel_dp);
> +
> + /* Disable port followed by PLL for next retry/clean up */
> + encoder->post_disable(encoder);
> + intel_disable_shared_dpll(crtc);
> +
> + } while (!intel_dp->train_set_valid &&
> + !intel_dp_get_link_retry_params(&lane_count, &link_bw));
> +
> + /* Reset pll state as before */
> + pll->config.crtc_mask &= ~(1 << crtc->pipe);
> + pll->config.hw_state = tmp_dpll_hw_state;
> +
> +exit:
> + /* Reset local associations made */
> + if (drm_crtc)
> + encoder->base.crtc = NULL;
> + crtc->config = tmp_crtc_config;
> +
> + DRM_DEBUG_KMS("Upfront link train %s: lanes:%d bw:%d\n",
> + intel_dp->train_set_valid ? "Passed" : "Failed", lane_count, link_bw);
> +
> + return intel_dp->train_set_valid;
> +}
> +
> void intel_ddi_init(struct drm_device *dev, enum port port)
> {
> struct drm_i915_private *dev_priv = dev->dev_private;
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index d8f7830..47b6266 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4622,6 +4622,71 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
> intel_dp->has_audio = false;
> }
>
> +static void intel_dp_upfront_dpms_off(struct drm_connector *connector,
> + struct drm_modeset_acquire_ctx *ctx)
> +{
> + struct intel_dp *intel_dp = intel_attached_dp(connector);
> + struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> + struct drm_crtc *crtc = intel_dig_port->base.base.crtc;
> + struct intel_load_detect_pipe tmp;
> +
> + if (intel_get_load_detect_pipe(connector, NULL, &tmp, ctx)) {
> + crtc->acquire_ctx = ctx;
> + tmp.dpms_mode = DRM_MODE_DPMS_OFF;
> + intel_release_load_detect_pipe(connector, &tmp, ctx);
> + }
> +}
> +
> +static void intel_dp_upfront_dpms_on(struct drm_connector *connector,
> + struct drm_modeset_acquire_ctx *ctx)
> +{
> + struct intel_load_detect_pipe tmp;
> +
> + intel_get_load_detect_pipe(connector, NULL, &tmp, ctx);
> +
> + drm_modeset_drop_locks(ctx);
> + drm_modeset_acquire_fini(ctx);
> +}
> +
> +static bool intel_dp_upfront_link_train(struct drm_connector *connector)
> +{
> + struct intel_dp *intel_dp = intel_attached_dp(connector);
> + struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> + struct intel_encoder *intel_encoder = &intel_dig_port->base;
> + struct drm_device *dev = intel_encoder->base.dev;
> + struct drm_crtc *crtc = intel_dig_port->base.base.crtc;
> + struct intel_crtc *intel_crtc = crtc ? to_intel_crtc(crtc) : NULL;
> + struct drm_modeset_acquire_ctx ctx, *old_ctx = NULL;
> + bool ret = true, need_dpms_on = false;
> +
> + if (!IS_BROXTON(dev))
> + return true;
> + /*
> + * On hotplug cases, we call _upfront_link_train directly.
> + * In connected boot scenarios (boot with {MIPI/eDP} + DP),
> + * BIOS typically brings up DP. Hence, we disable the crtc
> + * to do _upfront_link_training and then re-enable it back.
> + */
> + if (crtc && crtc->enabled && intel_crtc->active) {
> + DRM_DEBUG_KMS("Disabling pipe %c\n", pipe_name(intel_crtc->pipe));
> + old_ctx = crtc->acquire_ctx;
> + drm_modeset_acquire_init(&ctx, 0);
> + intel_dp_upfront_dpms_off(connector, &ctx);
> + need_dpms_on = true;
> + }
> +
> + if (HAS_DDI(dev))
> + ret = intel_ddi_upfront_link_train(intel_dp, intel_crtc);
> + /* Other platforms upfront link train call goes here..*/
> +
> + if (need_dpms_on) {
> + intel_dp_upfront_dpms_on(connector, &ctx);
> + crtc->acquire_ctx = old_ctx;
> + }
> + return ret;
> +}
> +
> +
> static enum drm_connector_status
> intel_dp_detect(struct drm_connector *connector, bool force)
> {
> @@ -4631,7 +4696,7 @@ intel_dp_detect(struct drm_connector *connector, bool force)
> struct drm_device *dev = connector->dev;
> enum drm_connector_status status;
> enum intel_display_power_domain power_domain;
> - bool ret;
> + bool ret, do_upfront_link_train;
> u8 sink_irq_vector;
>
> DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> @@ -4705,6 +4770,16 @@ intel_dp_detect(struct drm_connector *connector, bool force)
> DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
> }
>
> + /* Do not do upfront link train, if it is a compliance request */
> + do_upfront_link_train =
> + intel_encoder->type == INTEL_OUTPUT_DISPLAYPORT &&
> + intel_dp->compliance_test_type != DP_TEST_LINK_TRAINING;
> +
> + if (do_upfront_link_train) {
> + ret = intel_dp_upfront_link_train(connector);
> + if (!ret)
> + status = connector_status_disconnected;
> + }
> out:
> intel_display_power_put(to_i915(dev), power_domain);
> return status;
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 5912955..3cfab20 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1025,6 +1025,8 @@ void intel_ddi_clock_get(struct intel_encoder *encoder,
> struct intel_crtc_state *pipe_config);
> void intel_ddi_set_vc_payload_alloc(struct drm_crtc *crtc, bool state);
> uint32_t ddi_signal_levels(struct intel_dp *intel_dp);
> +bool intel_ddi_upfront_link_train(struct intel_dp *intel_dp,
> + struct intel_crtc *crtc);
>
> /* intel_frontbuffer.c */
> void intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
> --
> 1.9.1
>
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