drm/i915/dp: consolidate AUX retry code

When checking link status during a hot plug event or detecting sink
presence, we need to retry 3 times per the spec (section 9.1 of the 1.1a
DisplayPort spec).  Consolidate the retry code into a
native_aux_read_retry function for use by get_link_status and _detect.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 5f97c17..bca48b0 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1012,21 +1012,23 @@ intel_dp_dpms(struct drm_encoder *encoder, int mode)
 }
 
 /*
- * Fetch AUX CH registers 0x202 - 0x207 which contain
- * link status information
+ * Native read with retry for link status and receiver capability reads for
+ * cases where the sink may still be asleep.
  */
 static bool
-intel_dp_get_link_status(struct intel_dp *intel_dp)
+intel_dp_aux_native_read_retry(struct intel_dp *intel_dp, uint16_t address,
+                              uint8_t *recv, int recv_bytes)
 {
        int ret, i;
 
-       /* Must try AUX reads for this at least 3 times */
+       /*
+        * Sinks are *supposed* to come up within 1ms from an off state,
+        * but we're also supposed to retry 3 times per the spec.
+        */
        for (i = 0; i < 3; i++) {
-               ret = intel_dp_aux_native_read(intel_dp,
-                                              DP_LANE0_1_STATUS,
-                                              intel_dp->link_status,
-                                              DP_LINK_STATUS_SIZE);
-               if (ret == DP_LINK_STATUS_SIZE)
+               ret = intel_dp_aux_native_read(intel_dp, address, recv,
+                                              recv_bytes);
+               if (ret == recv_bytes)
                        return true;
                msleep(1);
        }
@@ -1034,6 +1036,19 @@ intel_dp_get_link_status(struct intel_dp *intel_dp)
        return false;
 }
 
+/*
+ * Fetch AUX CH registers 0x202 - 0x207 which contain
+ * link status information
+ */
+static bool
+intel_dp_get_link_status(struct intel_dp *intel_dp)
+{
+       return intel_dp_aux_native_read_retry(intel_dp,
+                                             DP_LANE0_1_STATUS,
+                                             intel_dp->link_status,
+                                             DP_LINK_STATUS_SIZE);
+}
+
 static uint8_t
 intel_dp_link_status(uint8_t link_status[DP_LINK_STATUS_SIZE],
                     int r)
@@ -1549,7 +1564,7 @@ static enum drm_connector_status
 ironlake_dp_detect(struct intel_dp *intel_dp)
 {
        enum drm_connector_status status;
-       int ret, i;
+       bool ret;
 
        /* Can't disconnect eDP, but you can close the lid... */
        if (is_edp(intel_dp)) {
@@ -1560,17 +1575,11 @@ ironlake_dp_detect(struct intel_dp *intel_dp)
        }
 
        status = connector_status_disconnected;
-       for (i = 0; i < 3; i++) {
-               ret = intel_dp_aux_native_read(intel_dp,
-                                              0x000, intel_dp->dpcd,
-                                              sizeof (intel_dp->dpcd));
-               if (ret == sizeof(intel_dp->dpcd) &&
-                   intel_dp->dpcd[DP_DPCD_REV] != 0) {
-                       status = connector_status_connected;
-                       break;
-               }
-               msleep(1);
-       }
+       ret = intel_dp_aux_native_read_retry(intel_dp,
+                                            0x000, intel_dp->dpcd,
+                                            sizeof (intel_dp->dpcd));
+       if (ret && intel_dp->dpcd[DP_DPCD_REV] != 0)
+               status = connector_status_connected;
        DRM_DEBUG_KMS("DPCD: %hx%hx%hx%hx\n", intel_dp->dpcd[0],
                      intel_dp->dpcd[1], intel_dp->dpcd[2], intel_dp->dpcd[3]);
        return status;