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

[Durgadoss R <durgadoss.r@intel.com>]

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.

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