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author | Nathan Ciobanu <nathan.d.ciobanu@linux.intel.com> | 2018-07-20 14:44:12 -0700 |
---|---|---|
committer | Rodrigo Vivi <rodrigo.vivi@intel.com> | 2018-07-23 15:59:44 -0700 |
commit | bb5ffe6fd58cd37f1cade411c4a00745ed0fbbd1 (patch) | |
tree | 719ae49779ba112d826a0c3da50ab19eda591ebe /drivers/gpu/drm/i915/intel_dp_link_training.c | |
parent | 4eaf317a60fbea0555b936035002ca9bd9b9105d (diff) | |
download | linux-stable-bb5ffe6fd58cd37f1cade411c4a00745ed0fbbd1.tar.gz linux-stable-bb5ffe6fd58cd37f1cade411c4a00745ed0fbbd1.tar.bz2 linux-stable-bb5ffe6fd58cd37f1cade411c4a00745ed0fbbd1.zip |
drm/i915/dp: Limit link training clock recovery loop
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
Changes in v5:
- Removed DP_DP14_MAX_CR_TRIES from drm
v6: Updated comment to match kernel style (Rodrigo)
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>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180720214413.29506-1-rodrigo.vivi@intel.com
Diffstat (limited to 'drivers/gpu/drm/i915/intel_dp_link_training.c')
-rw-r--r-- | drivers/gpu/drm/i915/intel_dp_link_training.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c index 4da6e33c7fa1..299cad5632ed 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_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 +170,20 @@ intel_dp_link_training_clock_recovery(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 = 10; + 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 +227,8 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp) ++max_vswing_tries; } + DRM_ERROR("Failed clock recovery %d times, giving up!\n", max_cr_tries); + return false; } /* |