drm/i915/dp: generate and cache sink rate array for all DP, not just eDP 1.4

There is some conflation related to sink rates, making this change more
complicated than it would otherwise have to be. There are three changes
here that are rather difficult to split up:

1) Use the intel_dp->sink_rates array for all DP, not just eDP 1.4. We
   initialize it from DPCD on eDP 1.4 like before, but generate it based
   on DP_MAX_LINK_RATE on others. This reduces code complexity when we
   need to use the sink rates; they are all always in the sink_rates
   array.

2) Update the sink rate array whenever we read DPCD, and use the
   information from there. This increases code readability when we need
   the sink rates.

3) Disentangle fallback rate limiting from sink rates. In the code, the
   max rate is a dynamic property of the *link*, not of the *sink*. Do
   the limiting after intersecting the source and sink rates, which are
   static properties of the devices.

This paves the way for follow-up refactoring that I've refrained from
doing here to keep this change as simple as it possibly can.

v2: introduce use_rate_select and handle non-confirming eDP (Ville)

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/071bad76467f8ab2e73f3f61ad52d5a468004c71.1490712890.git.jani.nikula@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -133,6 +133,34 @@ static void vlv_steal_power_sequencer(struct drm_device *dev,
 				      enum pipe pipe);
 static void intel_dp_unset_edid(struct intel_dp *intel_dp);
 
+static int intel_dp_num_rates(u8 link_bw_code)
+{
+	switch (link_bw_code) {
+	default:
+		WARN(1, "invalid max DP link bw val %x, using 1.62Gbps\n",
+		     link_bw_code);
+	case DP_LINK_BW_1_62:
+		return 1;
+	case DP_LINK_BW_2_7:
+		return 2;
+	case DP_LINK_BW_5_4:
+		return 3;
+	}
+}
+
+/* update sink rates from dpcd */
+static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
+{
+	int i, num_rates;
+
+	num_rates = intel_dp_num_rates(intel_dp->dpcd[DP_MAX_LINK_RATE]);
+
+	for (i = 0; i < num_rates; i++)
+		intel_dp->sink_rates[i] = default_rates[i];
+
+	intel_dp->num_sink_rates = num_rates;
+}
+
 static int
 intel_dp_max_link_bw(struct intel_dp  *intel_dp)
 {
@@ -205,19 +233,6 @@ intel_dp_downstream_max_dotclock(struct intel_dp *intel_dp)
 	return max_dotclk;
 }
 
-static int
-intel_dp_sink_rates(struct intel_dp *intel_dp, const int **sink_rates)
-{
-	if (intel_dp->num_sink_rates) {
-		*sink_rates = intel_dp->sink_rates;
-		return intel_dp->num_sink_rates;
-	}
-
-	*sink_rates = default_rates;
-
-	return (intel_dp->max_sink_link_bw >> 3) + 1;
-}
-
 static void
 intel_dp_set_source_rates(struct intel_dp *intel_dp)
 {
@@ -286,15 +301,22 @@ static int intel_dp_rate_index(const int *rates, int len, int rate)
 static int intel_dp_common_rates(struct intel_dp *intel_dp,
 				 int *common_rates)
 {
-	const int *sink_rates;
-	int sink_len;
-
-	sink_len = intel_dp_sink_rates(intel_dp, &sink_rates);
+	int max_rate = drm_dp_bw_code_to_link_rate(intel_dp->max_sink_link_bw);
+	int i, common_len;
 
-	return intersect_rates(intel_dp->source_rates,
+	common_len = intersect_rates(intel_dp->source_rates,
 				     intel_dp->num_source_rates,
-			       sink_rates, sink_len,
+				     intel_dp->sink_rates,
+				     intel_dp->num_sink_rates,
 				     common_rates);
+
+	/* Limit results by potentially reduced max rate */
+	for (i = 0; i < common_len; i++) {
+		if (common_rates[common_len - i - 1] <= max_rate)
+			return common_len - i;
+	}
+
+	return 0;
 }
 
 static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
@@ -1498,8 +1520,7 @@ static void snprintf_int_array(char *str, size_t len,
 
 static void intel_dp_print_rates(struct intel_dp *intel_dp)
 {
-	const int *sink_rates;
-	int sink_len, common_len;
+	int common_len;
 	int common_rates[DP_MAX_SUPPORTED_RATES];
 	char str[128]; /* FIXME: too big for stack? */
 
@@ -1510,8 +1531,8 @@ static void intel_dp_print_rates(struct intel_dp *intel_dp)
 			   intel_dp->source_rates, intel_dp->num_source_rates);
 	DRM_DEBUG_KMS("source rates: %s\n", str);
 
-	sink_len = intel_dp_sink_rates(intel_dp, &sink_rates);
-	snprintf_int_array(str, sizeof(str), sink_rates, sink_len);
+	snprintf_int_array(str, sizeof(str),
+			   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);
@@ -1577,7 +1598,8 @@ int intel_dp_rate_select(struct intel_dp *intel_dp, int rate)
 void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
 			   uint8_t *link_bw, uint8_t *rate_select)
 {
-	if (intel_dp->num_sink_rates) {
+	/* eDP 1.4 rate select method. */
+	if (intel_dp->use_rate_select) {
 		*link_bw = 0;
 		*rate_select =
 			intel_dp_rate_select(intel_dp, port_clock);
@@ -3702,6 +3724,11 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 		intel_dp->num_sink_rates = i;
 	}
 
+	if (intel_dp->num_sink_rates)
+		intel_dp->use_rate_select = true;
+	else
+		intel_dp_set_sink_rates(intel_dp);
+
 	return true;
 }
 
@@ -3712,6 +3739,10 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 	if (!intel_dp_read_dpcd(intel_dp))
 		return false;
 
+	/* Don't clobber cached eDP rates. */
+	if (!is_edp(intel_dp))
+		intel_dp_set_sink_rates(intel_dp);
+
 	if (drm_dp_dpcd_read(&intel_dp->aux, DP_SINK_COUNT,
 			     &intel_dp->sink_count, 1) < 0)
 		return false;

drivers/gpu/drm/i915/intel_dp_link_training.c

@@ -146,7 +146,8 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 		link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
 	drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
 
-	if (intel_dp->num_sink_rates)
+	/* eDP 1.4 rate select method. */
+	if (!link_bw)
 		drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
 				  &rate_select, 1);
 

drivers/gpu/drm/i915/intel_drv.h

@@ -952,9 +952,10 @@ struct intel_dp {
 	/* source rates */
 	int num_source_rates;
 	const int *source_rates;
-	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
-	uint8_t num_sink_rates;
+	/* sink rates as reported by DP_MAX_LINK_RATE/DP_SUPPORTED_LINK_RATES */
+	int num_sink_rates;
 	int sink_rates[DP_MAX_SUPPORTED_RATES];
+	bool use_rate_select;
 	/* 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 */