Limit the link training clock recovery loop to 10 failed attempts at
LANEx_CR_DONE per DP 1.4 spec. Some USB-C MST hubs cause us to get
stuck in this loop on hot-plugging indefinitely as
drm_dp_clock_recovery_ok() never returns true and none of the
other conditions occur.
Signed-off-by: Nathan Ciobanu <nathan.d.ciob...@linux.intel.com>
---
drivers/gpu/drm/i915/intel_dp_link_training.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
b/drivers/gpu/drm/i915/intel_dp_link_training.c
index 4da6e33c7fa1..66c1a70343ba 100644
--- a/drivers/gpu/drm/i915/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
@@ -129,7 +129,7 @@ static bool intel_dp_link_max_vswing_reached(struct
intel_dp *intel_dp)
intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
{
uint8_t voltage;
- int voltage_tries, max_vswing_tries;
+ int voltage_tries, max_vswing_tries, cr_tries;
uint8_t link_config[2];
uint8_t link_bw, rate_select;
@@ -172,6 +172,7 @@ static bool intel_dp_link_max_vswing_reached(struct
intel_dp *intel_dp)
voltage_tries = 1;
max_vswing_tries = 0;
+ cr_tries = 0;
for (;;) {
uint8_t link_status[DP_LINK_STATUS_SIZE];
@@ -215,6 +216,11 @@ static bool intel_dp_link_max_vswing_reached(struct
intel_dp *intel_dp)
if (intel_dp_link_max_vswing_reached(intel_dp))
++max_vswing_tries;
+ if (cr_tries == 9) {
+ DRM_ERROR("Failed clock recovery 10 times, giving
up!\n");
+ return false;
+ }
+ ++cr_tries;
}
}
--
1.9.1
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