[Intel-gfx] [PATCH 5/7] drm/i915/dp: Add methods to update link train params

[Durgadoss R]

Retrying with reduced lanes/bw and updating the final
available lanes/bw to DPCD is needed for upfront link
train logic. Hence, this patch adds these methods
and exports them so that these can be called from
other files like ddi.c/display.c.

Signed-off-by: Durgadoss R <durgadoss.r at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c  | 34 ++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  2 ++
 2 files changed, 36 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index f335c92..d8f7830 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1660,6 +1660,40 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
 	intel_dp->lane_count = pipe_config->lane_count;
 }
 
+void intel_dp_update_dpcd_params(struct intel_dp *intel_dp)
+{
+	intel_dp->dpcd[DP_MAX_LANE_COUNT] &= ~DP_MAX_LANE_COUNT_MASK;
+	intel_dp->dpcd[DP_MAX_LANE_COUNT] |=
+			intel_dp->lane_count & DP_MAX_LANE_COUNT_MASK;
+
+	intel_dp->dpcd[DP_MAX_LINK_RATE] =
+			drm_dp_link_rate_to_bw_code(intel_dp->link_rate);
+}
+
+bool intel_dp_get_link_retry_params(uint8_t *lane_count, uint8_t *link_bw)
+{
+	/*
+	 * As per DP1.3 Spec, retry all link rates for a particular
+	 * lane count value, before reducing number of lanes.
+	 */
+	if (*link_bw == DP_LINK_BW_5_4) {
+		*link_bw = DP_LINK_BW_2_7;
+	} else if (*link_bw == DP_LINK_BW_2_7) {
+		*link_bw = DP_LINK_BW_1_62;
+	} else if (*lane_count == 4) {
+		*lane_count = 2;
+		*link_bw = DP_LINK_BW_5_4;
+	} else if (*lane_count == 2) {
+		*lane_count = 1;
+		*link_bw = DP_LINK_BW_5_4;
+	} else {
+		/* Tried all combinations, so exit */
+		return false;
+	}
+
+	return true;
+}
+
 static void intel_dp_prepare(struct intel_encoder *encoder)
 {
 	struct drm_device *dev = encoder->base.dev;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index faa91fc..5cefb0e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1233,6 +1233,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 			     struct intel_connector *intel_connector);
 void intel_dp_set_link_params(struct intel_dp *intel_dp,
 			      const struct intel_crtc_state *pipe_config);
+void intel_dp_update_dpcd_params(struct intel_dp *intel_dp);
+bool intel_dp_get_link_retry_params(uint8_t *lane_count, uint8_t *link_bw);
 void intel_dp_start_link_train(struct intel_dp *intel_dp);
 void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
-- 
1.9.1