Check if *NO_AUX_TRANSACTIONS_LINK_TRAINING* bit is set on DPCD registers. If this bit is set, we can reuse the known good drive current and pre-emphasis level from the last "full" link training. v2: Commit message update (Thierry) Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91393 Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx> --- drivers/gpu/drm/i915/intel_dp.c | 2 +- drivers/gpu/drm/i915/intel_dp_link_training.c | 19 +++++++++++++++++++ drivers/gpu/drm/i915/intel_drv.h | 1 + 3 files changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 6b36d82..3137187 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -3852,7 +3852,7 @@ intel_dp_link_down(struct intel_dp *intel_dp) intel_dp->DP = DP; } -static bool +bool intel_dp_get_dpcd(struct intel_dp *intel_dp) { struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp); diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c index 8f22c92..bcf2801 100644 --- a/drivers/gpu/drm/i915/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c @@ -85,6 +85,25 @@ static bool intel_dp_reset_link_train(struct intel_dp *intel_dp, uint8_t dp_train_pat) { + bool has_dpcd; + bool no_aux_handshake = false; + + has_dpcd = intel_dp_get_dpcd(intel_dp); + + /* + * Source device can try to use drive current and pre-emphasis + * parameters computed by the last "full" link training if the + * DP_NO_AUX_HANDSHAKE_LINK_TRAINING bit is set to 1. + */ + if (has_dpcd) { + if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11) { + no_aux_handshake = (intel_dp->dpcd[DP_MAX_DOWNSPREAD] & + DP_NO_AUX_HANDSHAKE_LINK_TRAINING); + } + } + + intel_dp->train_set_valid &= no_aux_handshake; + DRM_DEBUG_KMS("link training optimization: %s\n", yesno(intel_dp->train_set_valid)); diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h index 0438b57..918bdf1 100644 --- a/drivers/gpu/drm/i915/intel_drv.h +++ b/drivers/gpu/drm/i915/intel_drv.h @@ -1250,6 +1250,7 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc); bool intel_dp_compute_config(struct intel_encoder *encoder, struct intel_crtc_state *pipe_config); bool intel_dp_is_edp(struct drm_device *dev, enum port port); +bool intel_dp_get_dpcd(struct intel_dp *intel_dp); enum irqreturn intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd); void intel_edp_backlight_on(struct intel_dp *intel_dp); -- 1.9.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
