- u8 status;
- int ret;
- int count = 0;
-
- do {
- ret = drm_dp_dpcd_readb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
-
- if (ret < 0) {
- DRM_DEBUG_KMS("failed to read payload table status %d\n", ret);
- goto fail;
- }
-
- if (status & DP_PAYLOAD_ACT_HANDLED)
- break;
- count++;
- udelay(100);
-
- } while (count < 30);
-
- if (!(status & DP_PAYLOAD_ACT_HANDLED)) {
- DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n", status, count);
- ret = -EINVAL;
- goto fail;
+ /*
+ * There doesn't seem to be any recommended retry count or timeout in
+ * the MST specification. Since some hubs have been observed to take
+ * over 1 second to update their payload allocations under certain
+ * conditions, we use a rather large timeout value.
+ */
+ const int timeout_ms = 3000;
+ int ret, status;
+
+ ret = readx_poll_timeout(do_get_act_status, mgr->aux, status,
+ status & DP_PAYLOAD_ACT_HANDLED || status < 0,
+ 200, timeout_ms * USEC_PER_MSEC);
+ if (ret < 0 && status >= 0) {
+ DRM_ERROR("Failed to get ACT after %dms, last status: %02x\n",
+ timeout_ms, status);
+ return -EINVAL;
+ } else if (status < 0) {
+ /*
+ * Failure here isn't unexpected - the hub may have
+ * just been unplugged
+ */
+ DRM_DEBUG_KMS("Failed to read payload table status: %d\n",
+ status);
+ return status;