Re: [PATCH 7/7] drm/i915/dp: Enable Upfront link training for typeC DP support on BXT

[Jim Bride <jim.bride@linux.intel.com>]

On Wed, Dec 30, 2015 at 09:48:43AM +1000, Dave Airlie wrote:
> On 11 Dec 2015 7:09 PM, "Durgadoss R" <durgadoss.r@intel.com> 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.

Based on conversations I've had with folks in VPG, Windows appears to do
upfront link training at plug time.

Jim



> Dave.
> 
> >
> > Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
> > ---
> >  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
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx

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