@@ -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, max_cr_tries;
uint8_t link_config[2];
uint8_t link_bw, rate_select;
@@ -170,9 +170,19 @@ static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
return false;
}
+ /* DP 1.4 spec clock recovery retries defined but
+ * for devices pre-DP 1.4 we set the retry limit
+ * to 4 (voltage levels) x 4 (preemphasis levels) x
+ * x 5 (same voltage retries) = 80 (max iterations)
+ */
+ if (intel_dp->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
+ max_cr_tries = DP_DP14_MAX_CR_TRIES;
+ else
+ max_cr_tries = 80;
+
voltage_tries = 1;
max_vswing_tries = 0;
- for (;;) {
+ for (cr_tries = 0; cr_tries < max_cr_tries; ++cr_tries) {
uint8_t link_status[DP_LINK_STATUS_SIZE];
drm_dp_link_train_clock_recovery_delay(intel_dp->dpcd);
@@ -216,6 +226,8 @@ static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
++max_vswing_tries;
}
+ DRM_ERROR("Failed clock recovery %d times, giving up!\n", max_cr_tries);
+ return false;
}
/*
@@ -820,6 +820,7 @@
#define DP_DP13_DPCD_REV 0x2200
#define DP_DP13_MAX_LINK_RATE 0x2201
+#define DP_DP14_MAX_CR_TRIES 10
#define DP_DPRX_FEATURE_ENUMERATION_LIST 0x2210 /* DP 1.3 */
# define DP_GTC_CAP (1 << 0) /* DP 1.3 */
Limit the link training clock recovery loop to 10 attempts at LANEx_CR_DONE per DP 1.4 spec section 3.5.1.2.2 and 80 attempts for pre-DP 1.4 (4 voltage levels x 4 preemphasis levels x x 5 identical voltages tries). Some faulty USB-C MST hubs can cause us to get stuck in this loop indefinitely requesting something like: voltage swing: 0, pre-emphasis level: 2 voltage swing: 1, pre-emphasis level: 2 voltage swing: 0, pre-emphasis level: 3 over and over so max_vswing would never be reached, drm_dp_clock_recovery_ok() would never return true and voltage_tries would always get reset to 1. The driver sends those values to the hub but the hub keeps requesting new values every time. Changes in v2: - updated commit message (DK, Manasi) - defined DP_DP14_MAX_CR_TRIES (Marc) - made the loop iterate for max 10 times (Rodrigo, Marc) Changes in v3: - changed error message to use DP_DP14_MAX_CR_TRIES Changes in v4: - Updated the title to reflect the change - Updated the commit message - Added 80 attempts for pre-DP 1.4 devices Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Marc Herbert <marc.herbert@intel.com> Cc: Manasi Navare <manasi.d.navare@intel.com> Signed-off-by: Nathan Ciobanu <nathan.d.ciobanu@linux.intel.com> --- drivers/gpu/drm/i915/intel_dp_link_training.c | 16 ++++++++++++++-- include/drm/drm_dp_helper.h | 1 + 2 files changed, 15 insertions(+), 2 deletions(-)