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Subject[PATCH 3.8 19/81] drm/i915/dp: add native aux defer retry limit
Date
3.8.13.20 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jani Nikula <jani.nikula@intel.com>

commit f51a44b9a6c4982cc25bfb3727de9bb893621ebc upstream.

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>
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/gpu/drm/i915/intel_dp.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 394fa61..64c9d7e 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -491,6 +491,7 @@ intel_dp_aux_native_write(struct intel_dp *intel_dp,
uint8_t msg[20];
int msg_bytes;
uint8_t ack;
+ int retry;

intel_dp_check_edp(intel_dp);
if (send_bytes > 16)
@@ -501,18 +502,20 @@ intel_dp_aux_native_write(struct intel_dp *intel_dp,
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)
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 */
@@ -534,6 +537,7 @@ intel_dp_aux_native_read(struct intel_dp *intel_dp,
int reply_bytes;
uint8_t ack;
int ret;
+ int retry;

intel_dp_check_edp(intel_dp);
msg[0] = AUX_NATIVE_READ << 4;
@@ -544,7 +548,7 @@ intel_dp_aux_native_read(struct intel_dp *intel_dp,
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)
@@ -561,6 +565,9 @@ intel_dp_aux_native_read(struct intel_dp *intel_dp,
else
return -EIO;
}
+
+ DRM_ERROR("too many retries, giving up\n");
+ return -EIO;
}

static int
--
1.8.3.2


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