drm/i915/dp: cache common rates with sink rates

Now that source rates are static and sink rates are updated whenever
DPCD is updated, we can do and cache the intersection of them whenever
sink rates are updated. This reduces code complexity, as we don't have
to keep calling the functions to intersect. We also get rid of several
common rates arrays on stack.

Limiting the common rates by a max link rate can be done by picking the
first N elements of the cached common rates.

v2: get rid of the local common_rates variable (Manasi)
v3: don't clobber cached eDP rates on short pulse (Ville)

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/e3b287e8cb6559b1f8fd4e80b78a8d22f1802eb7.1491485983.git.jani.nikula@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -284,17 +284,29 @@ static int intel_dp_rate_index(const int *rates, int len, int rate)
 	return -1;
 }
 
-static int intel_dp_common_rates(struct intel_dp *intel_dp,
-				 int *common_rates)
+static void intel_dp_set_common_rates(struct intel_dp *intel_dp)
 {
-	int max_rate = intel_dp->max_sink_link_rate;
-	int i, common_len;
+	WARN_ON(!intel_dp->num_source_rates || !intel_dp->num_sink_rates);
 
-	common_len = intersect_rates(intel_dp->source_rates,
-				     intel_dp->num_source_rates,
-				     intel_dp->sink_rates,
-				     intel_dp->num_sink_rates,
-				     common_rates);
+	intel_dp->num_common_rates = intersect_rates(intel_dp->source_rates,
+						     intel_dp->num_source_rates,
+						     intel_dp->sink_rates,
+						     intel_dp->num_sink_rates,
+						     intel_dp->common_rates);
+
+	/* Paranoia, there should always be something in common. */
+	if (WARN_ON(intel_dp->num_common_rates == 0)) {
+		intel_dp->common_rates[0] = default_rates[0];
+		intel_dp->num_common_rates = 1;
+	}
+}
+
+/* get length of common rates potentially limited by max_rate */
+static int intel_dp_common_len_rate_limit(struct intel_dp *intel_dp,
+					  int max_rate)
+{
+	const int *common_rates = intel_dp->common_rates;
+	int i, common_len = intel_dp->num_common_rates;
 
 	/* Limit results by potentially reduced max rate */
 	for (i = 0; i < common_len; i++) {
@@ -305,25 +317,23 @@ static int intel_dp_common_rates(struct intel_dp *intel_dp,
 	return 0;
 }
 
-static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
-				    int *common_rates, int link_rate)
+static int intel_dp_link_rate_index(struct intel_dp *intel_dp, int link_rate)
 {
 	int common_len;
 
-	common_len = intel_dp_common_rates(intel_dp, common_rates);
+	common_len = intel_dp_common_len_rate_limit(intel_dp,
+						    intel_dp->max_sink_link_rate);
 
-	return intel_dp_rate_index(common_rates, common_len, link_rate);
+	return intel_dp_rate_index(intel_dp->common_rates, common_len, link_rate);
 }
 
 int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 					    int link_rate, uint8_t lane_count)
 {
-	int common_rates[DP_MAX_SUPPORTED_RATES];
+	const int *common_rates = intel_dp->common_rates;
 	int link_rate_index;
 
-	link_rate_index = intel_dp_link_rate_index(intel_dp,
-						   common_rates,
-						   link_rate);
+	link_rate_index = intel_dp_link_rate_index(intel_dp, link_rate);
 	if (link_rate_index > 0) {
 		intel_dp->max_sink_link_rate = common_rates[link_rate_index - 1];
 		intel_dp->max_sink_lane_count = lane_count;
@@ -1506,8 +1516,6 @@ static void snprintf_int_array(char *str, size_t len,
 
 static void intel_dp_print_rates(struct intel_dp *intel_dp)
 {
-	int common_len;
-	int common_rates[DP_MAX_SUPPORTED_RATES];
 	char str[128]; /* FIXME: too big for stack? */
 
 	if ((drm_debug & DRM_UT_KMS) == 0)
@@ -1521,8 +1529,8 @@ static void intel_dp_print_rates(struct intel_dp *intel_dp)
 			   intel_dp->sink_rates, intel_dp->num_sink_rates);
 	DRM_DEBUG_KMS("sink rates: %s\n", str);
 
-	common_len = intel_dp_common_rates(intel_dp, common_rates);
-	snprintf_int_array(str, sizeof(str), common_rates, common_len);
+	snprintf_int_array(str, sizeof(str),
+			   intel_dp->common_rates, intel_dp->num_common_rates);
 	DRM_DEBUG_KMS("common rates: %s\n", str);
 }
 
@@ -1560,14 +1568,14 @@ bool intel_dp_read_desc(struct intel_dp *intel_dp)
 int
 intel_dp_max_link_rate(struct intel_dp *intel_dp)
 {
-	int rates[DP_MAX_SUPPORTED_RATES] = {};
 	int len;
 
-	len = intel_dp_common_rates(intel_dp, rates);
+	len = intel_dp_common_len_rate_limit(intel_dp,
+					     intel_dp->max_sink_link_rate);
 	if (WARN_ON(len <= 0))
 		return 162000;
 
-	return rates[len - 1];
+	return intel_dp->common_rates[len - 1];
 }
 
 int intel_dp_rate_select(struct intel_dp *intel_dp, int rate)
@@ -1636,11 +1644,11 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	int link_rate_index;
 	int bpp, mode_rate;
 	int link_avail, link_clock;
-	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
 	int common_len;
 	uint8_t link_bw, rate_select;
 
-	common_len = intel_dp_common_rates(intel_dp, common_rates);
+	common_len = intel_dp_common_len_rate_limit(intel_dp,
+						    intel_dp->max_sink_link_rate);
 
 	/* No common link rates between source and sink */
 	WARN_ON(common_len <= 0);
@@ -1678,7 +1686,6 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	/* Use values requested by Compliance Test Request */
 	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
 		link_rate_index = intel_dp_link_rate_index(intel_dp,
-							   common_rates,
 							   intel_dp->compliance.test_link_rate);
 		if (link_rate_index >= 0)
 			min_clock = max_clock = link_rate_index;
@@ -1686,7 +1693,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	}
 	DRM_DEBUG_KMS("DP link computation with max lane count %i "
 		      "max bw %d pixel clock %iKHz\n",
-		      max_lane_count, common_rates[max_clock],
+		      max_lane_count, intel_dp->common_rates[max_clock],
 		      adjusted_mode->crtc_clock);
 
 	/* Walk through all bpp values. Luckily they're all nicely spaced with 2
@@ -1722,7 +1729,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 				lane_count <= max_lane_count;
 				lane_count <<= 1) {
 
-				link_clock = common_rates[clock];
+				link_clock = intel_dp->common_rates[clock];
 				link_avail = intel_dp_max_data_rate(link_clock,
 								    lane_count);
 
@@ -1754,7 +1761,7 @@ found:
 	pipe_config->lane_count = lane_count;
 
 	pipe_config->pipe_bpp = bpp;
-	pipe_config->port_clock = common_rates[clock];
+	pipe_config->port_clock = intel_dp->common_rates[clock];
 
 	intel_dp_compute_rate(intel_dp, pipe_config->port_clock,
 			      &link_bw, &rate_select);
@@ -3715,6 +3722,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 	else
 		intel_dp_set_sink_rates(intel_dp);
 
+	intel_dp_set_common_rates(intel_dp);
+
 	return true;
 }
 
@@ -3726,8 +3735,10 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 		return false;
 
 	/* Don't clobber cached eDP rates. */
-	if (!is_edp(intel_dp))
+	if (!is_edp(intel_dp)) {
 		intel_dp_set_sink_rates(intel_dp);
+		intel_dp_set_common_rates(intel_dp);
+	}
 
 	if (drm_dp_dpcd_read(&intel_dp->aux, DP_SINK_COUNT,
 			     &intel_dp->sink_count, 1) < 0)
@@ -3950,7 +3961,6 @@ static uint8_t intel_dp_autotest_link_training(struct intel_dp *intel_dp)
 {
 	int status = 0;
 	int min_lane_count = 1;
-	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
 	int link_rate_index, test_link_rate;
 	uint8_t test_lane_count, test_link_bw;
 	/* (DP CTS 1.2)
@@ -3979,7 +3989,6 @@ static uint8_t intel_dp_autotest_link_training(struct intel_dp *intel_dp)
 	/* Validate the requested link rate */
 	test_link_rate = drm_dp_bw_code_to_link_rate(test_link_bw);
 	link_rate_index = intel_dp_link_rate_index(intel_dp,
-						   common_rates,
 						   test_link_rate);
 	if (link_rate_index < 0)
 		return DP_TEST_NAK;

drivers/gpu/drm/i915/intel_drv.h

@@ -956,6 +956,9 @@ struct intel_dp {
 	int num_sink_rates;
 	int sink_rates[DP_MAX_SUPPORTED_RATES];
 	bool use_rate_select;
+	/* intersection of source and sink rates */
+	int num_common_rates;
+	int common_rates[DP_MAX_SUPPORTED_RATES];
 	/* Max lane count for the sink as per DPCD registers */
 	uint8_t max_sink_lane_count;
 	/* Max link BW for the sink as per DPCD registers */