drm/i915: Add support for starting FRL training for HDMI2.1 via PCON

This patch adds functions to start FRL training for an HDMI2.1 sink,
connected via a PCON as a DP branch device.
This patch also adds a new structure for storing frl training related
data, when FRL training is completed.

v2: As suggested by Uma Shankar:
-renamed couple of variables for better clarity
-tweaked the macros used for correct semantics for true/false
-fixed other styling issues.

v3: Completed the TODO for condition for going to FRL mode.
Modified the condition to determine the required FRL b/w
based only on the Pcon and Sink's max FRL values.
Moved the frl structure initialization to intel_dp_init_connector().

v4: Fixed typo in initialization of frl structure.

v5: Always use FRL if its possible, instead of enabling only for
higher modes as done in v3.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com> (v2)
[Jani: Fixed checkpatch BRACES, CONSTANT_COMPARISON.]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201218103723.30844-10-ankit.k.nautiyal@intel.com

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1321,6 +1321,11 @@ struct intel_dp_compliance {
 	u8 test_lane_count;
 };
 
+struct intel_dp_pcon_frl {
+	bool is_trained;
+	int trained_rate_gbps;
+};
+
 struct intel_dp {
 	i915_reg_t output_reg;
 	u32 DP;
@@ -1442,6 +1447,8 @@ struct intel_dp {
 
 	bool hobl_failed;
 	bool hobl_active;
+
+	struct intel_dp_pcon_frl frl;
 };
 
 enum lspcon_vendor {

drivers/gpu/drm/i915/display/intel_dp.c

@@ -3879,6 +3879,8 @@ static void intel_disable_dp(struct intel_atomic_state *state,
 	intel_edp_backlight_off(old_conn_state);
 	intel_dp_set_power(intel_dp, DP_SET_POWER_D3);
 	intel_edp_panel_off(intel_dp);
+	intel_dp->frl.is_trained = false;
+	intel_dp->frl.trained_rate_gbps = 0;
 }
 
 static void g4x_disable_dp(struct intel_atomic_state *state,
@@ -3974,6 +3976,152 @@ cpt_set_link_train(struct intel_dp *intel_dp,
 	intel_de_posting_read(dev_priv, intel_dp->output_reg);
 }
 
+static int intel_dp_pcon_get_frl_mask(u8 frl_bw_mask)
+{
+	int bw_gbps[] = {9, 18, 24, 32, 40, 48};
+	int i;
+
+	for (i = ARRAY_SIZE(bw_gbps) - 1; i >= 0; i--) {
+		if (frl_bw_mask & (1 << i))
+			return bw_gbps[i];
+	}
+	return 0;
+}
+
+static int intel_dp_pcon_set_frl_mask(int max_frl)
+{
+	switch (max_frl) {
+	case 48:
+		return DP_PCON_FRL_BW_MASK_48GBPS;
+	case 40:
+		return DP_PCON_FRL_BW_MASK_40GBPS;
+	case 32:
+		return DP_PCON_FRL_BW_MASK_32GBPS;
+	case 24:
+		return DP_PCON_FRL_BW_MASK_24GBPS;
+	case 18:
+		return DP_PCON_FRL_BW_MASK_18GBPS;
+	case 9:
+		return DP_PCON_FRL_BW_MASK_9GBPS;
+	}
+
+	return 0;
+}
+
+static int intel_dp_hdmi_sink_max_frl(struct intel_dp *intel_dp)
+{
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	struct drm_connector *connector = &intel_connector->base;
+
+	return (connector->display_info.hdmi.max_frl_rate_per_lane *
+		connector->display_info.hdmi.max_lanes);
+}
+
+static int intel_dp_pcon_start_frl_training(struct intel_dp *intel_dp)
+{
+#define PCON_EXTENDED_TRAIN_MODE (1 > 0)
+#define PCON_CONCURRENT_MODE (1 > 0)
+#define PCON_SEQUENTIAL_MODE !PCON_CONCURRENT_MODE
+#define PCON_NORMAL_TRAIN_MODE !PCON_EXTENDED_TRAIN_MODE
+#define TIMEOUT_FRL_READY_MS 500
+#define TIMEOUT_HDMI_LINK_ACTIVE_MS 1000
+
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	int max_frl_bw, max_pcon_frl_bw, max_edid_frl_bw, ret;
+	u8 max_frl_bw_mask = 0, frl_trained_mask;
+	bool is_active;
+
+	ret = drm_dp_pcon_reset_frl_config(&intel_dp->aux);
+	if (ret < 0)
+		return ret;
+
+	max_pcon_frl_bw = intel_dp->dfp.pcon_max_frl_bw;
+	drm_dbg(&i915->drm, "PCON max rate = %d Gbps\n", max_pcon_frl_bw);
+
+	max_edid_frl_bw = intel_dp_hdmi_sink_max_frl(intel_dp);
+	drm_dbg(&i915->drm, "Sink max rate from EDID = %d Gbps\n", max_edid_frl_bw);
+
+	max_frl_bw = min(max_edid_frl_bw, max_pcon_frl_bw);
+
+	if (max_frl_bw <= 0)
+		return -EINVAL;
+
+	ret = drm_dp_pcon_frl_prepare(&intel_dp->aux, false);
+	if (ret < 0)
+		return ret;
+	/* Wait for PCON to be FRL Ready */
+	wait_for(is_active = drm_dp_pcon_is_frl_ready(&intel_dp->aux) == true, TIMEOUT_FRL_READY_MS);
+
+	if (!is_active)
+		return -ETIMEDOUT;
+
+	max_frl_bw_mask = intel_dp_pcon_set_frl_mask(max_frl_bw);
+	ret = drm_dp_pcon_frl_configure_1(&intel_dp->aux, max_frl_bw, PCON_SEQUENTIAL_MODE);
+	if (ret < 0)
+		return ret;
+	ret = drm_dp_pcon_frl_configure_2(&intel_dp->aux, max_frl_bw_mask, PCON_NORMAL_TRAIN_MODE);
+	if (ret < 0)
+		return ret;
+	ret = drm_dp_pcon_frl_enable(&intel_dp->aux);
+	if (ret < 0)
+		return ret;
+	/*
+	 * Wait for FRL to be completed
+	 * Check if the HDMI Link is up and active.
+	 */
+	wait_for(is_active = drm_dp_pcon_hdmi_link_active(&intel_dp->aux) == true, TIMEOUT_HDMI_LINK_ACTIVE_MS);
+
+	if (!is_active)
+		return -ETIMEDOUT;
+
+	/* Verify HDMI Link configuration shows FRL Mode */
+	if (drm_dp_pcon_hdmi_link_mode(&intel_dp->aux, &frl_trained_mask) !=
+	    DP_PCON_HDMI_MODE_FRL) {
+		drm_dbg(&i915->drm, "HDMI couldn't be trained in FRL Mode\n");
+		return -EINVAL;
+	}
+	drm_dbg(&i915->drm, "MAX_FRL_MASK = %u, FRL_TRAINED_MASK = %u\n", max_frl_bw_mask, frl_trained_mask);
+
+	intel_dp->frl.trained_rate_gbps = intel_dp_pcon_get_frl_mask(frl_trained_mask);
+	intel_dp->frl.is_trained = true;
+	drm_dbg(&i915->drm, "FRL trained with : %d Gbps\n", intel_dp->frl.trained_rate_gbps);
+
+	return 0;
+}
+
+static bool intel_dp_is_hdmi_2_1_sink(struct intel_dp *intel_dp)
+{
+	if (drm_dp_is_branch(intel_dp->dpcd) &&
+	    intel_dp->has_hdmi_sink &&
+	    intel_dp_hdmi_sink_max_frl(intel_dp) > 0)
+		return true;
+
+	return false;
+}
+
+void intel_dp_check_frl_training(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+
+	/* Always go for FRL training if supported */
+	if (!intel_dp_is_hdmi_2_1_sink(intel_dp) ||
+	    intel_dp->frl.is_trained)
+		return;
+
+	if (intel_dp_pcon_start_frl_training(intel_dp) < 0) {
+		int ret, mode;
+
+		drm_dbg(&dev_priv->drm, "Couldnt set FRL mode, continuing with TMDS mode\n");
+		ret = drm_dp_pcon_reset_frl_config(&intel_dp->aux);
+		mode = drm_dp_pcon_hdmi_link_mode(&intel_dp->aux, NULL);
+
+		if (ret < 0 || mode != DP_PCON_HDMI_MODE_TMDS)
+			drm_dbg(&dev_priv->drm, "Issue with PCON, cannot set TMDS mode\n");
+	} else {
+		drm_dbg(&dev_priv->drm, "FRL training Completed\n");
+	}
+}
+
 static void
 g4x_set_link_train(struct intel_dp *intel_dp,
 		   const struct intel_crtc_state *crtc_state,
@@ -8172,6 +8320,9 @@ intel_dp_init_connector(struct intel_digital_port *dig_port,
 			       (temp & ~0xf) | 0xd);
 	}
 
+	intel_dp->frl.is_trained = false;
+	intel_dp->frl.trained_rate_gbps = 0;
+
 	return true;
 
 fail:

drivers/gpu/drm/i915/display/intel_dp.h

@@ -144,4 +144,6 @@ bool intel_dp_initial_fastset_check(struct intel_encoder *encoder,
 void intel_dp_sync_state(struct intel_encoder *encoder,
 			 const struct intel_crtc_state *crtc_state);
 
+void intel_dp_check_frl_training(struct intel_dp *intel_dp);
+
 #endif /* __INTEL_DP_H__ */