I think I found what triggers the error (of course, this is just the
manifestation of the error, maybe not the root cause):
from 3.13.0-17.37 a limited number of "retries" has been introduced, which
fails after 7 retries; this seems to be not enough:
--- linux-3.13.0/drivers/gpu/drm/i915/intel_dp.c
+++ linux-3.13.0/drivers/gpu/drm/i915/intel_dp.c
@@ -537,6 +537,7 @@
uint8_t msg[20];
int msg_bytes;
uint8_t ack;
+ int retry;
if (WARN_ON(send_bytes > 16))
return -E2BIG;
@@ -548,18 +549,20 @@
msg[3] = send_bytes - 1;
memcpy(&msg[4], send, send_bytes);
msg_bytes = send_bytes + 4;
- for (;;) {
+ for (retry = 0; retry < 7; retry++) {
ret = intel_dp_aux_ch(intel_dp, msg, msg_bytes, &ack, 1);
if (ret < 0)
return ret;
if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK)
- break;
+ return send_bytes;
else if ((ack & AUX_NATIVE_REPLY_MASK) ==
AUX_NATIVE_REPLY_DEFER)
- udelay(100);
+ usleep_range(400, 500);
else
return -EIO;
}
- return send_bytes;
+
+ DRM_ERROR("too many retries, giving up\n");
+ return -EIO;
}
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https://bugs.launchpad.net/bugs/1322644
Title:
[Dell XPS 13 (L321X)] External monitor does not wake up after sleep
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