The Displayport Link Layer Compliance Testing Specification 1.2 rev 1.1 specifies that repeated AUX transactions after a failure (no response / invalid response) must have a minimum delay of 400us before the resend can occur. Tests 4.2.1.1 and 4.2.1.2 are two tests that require this specifically.
V2: - Changed udelay() to usleep_range() V3: - Removed extraneous check for timeout - Updated comment to reflect this change Signed-off-by: Todd Previte <tprev...@gmail.com> --- drivers/gpu/drm/i915/intel_dp.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index ed2f60c..dc87276 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -877,9 +877,15 @@ intel_dp_aux_ch(struct intel_dp *intel_dp, DP_AUX_CH_CTL_TIME_OUT_ERROR | DP_AUX_CH_CTL_RECEIVE_ERROR); - if (status & (DP_AUX_CH_CTL_TIME_OUT_ERROR | - DP_AUX_CH_CTL_RECEIVE_ERROR)) + /* DP CTS 1.2 Core Rev 1.1, 4.2.1.1 & 4.2.1.2 + 400us delay required for errors and timeouts + Timeout errors from the HW already meet this + requirement so skip to next iteration + */ + if (status & DP_AUX_CH_CTL_RECEIVE_ERROR) { + usleep_range(400, 500); continue; + } if (status & DP_AUX_CH_CTL_DONE) break; } -- 1.9.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx