drm/i915/dp: add native aux defer retry limit
Retrying indefinitely places too much trust on the aux implementation of
the sink devices.
Reported-by: Daniel Martin <consume.noise@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71267
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Cc: stable@vger.kernel.org
Tested-by: Theodore Ts'o <tytso@mit.edu>
Tested-by: Sree Harsha Totakura <freedesktop@h.totakura.in>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index c3696048..57552eb 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/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;
@@ -548,19 +549,21 @@
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;
ack >>= 4;
if ((ack & DP_AUX_NATIVE_REPLY_MASK) == DP_AUX_NATIVE_REPLY_ACK)
- break;
+ return send_bytes;
else if ((ack & DP_AUX_NATIVE_REPLY_MASK) == DP_AUX_NATIVE_REPLY_DEFER)
usleep_range(400, 500);
else
return -EIO;
}
- return send_bytes;
+
+ DRM_ERROR("too many retries, giving up\n");
+ return -EIO;
}
/* Write a single byte to the aux channel in native mode */
@@ -582,6 +585,7 @@
int reply_bytes;
uint8_t ack;
int ret;
+ int retry;
if (WARN_ON(recv_bytes > 19))
return -E2BIG;
@@ -595,7 +599,7 @@
msg_bytes = 4;
reply_bytes = recv_bytes + 1;
- for (;;) {
+ for (retry = 0; retry < 7; retry++) {
ret = intel_dp_aux_ch(intel_dp, msg, msg_bytes,
reply, reply_bytes);
if (ret == 0)
@@ -612,6 +616,9 @@
else
return -EIO;
}
+
+ DRM_ERROR("too many retries, giving up\n");
+ return -EIO;
}
static int