From d13e2a6e95e6b87f571c837c71a3d05691def9bb Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Mon, 8 Jul 2024 22:00:24 +0300 Subject: drm/i915/dp: Reset intel_dp->link_trained before retraining the link MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Regularly retraining a link during an atomic commit happens with the given pipe/link already disabled and hence intel_dp->link_trained being false. Ensure this also for retraining a DP SST link via direct calls to the link training functions (vs. an actual commit as for DP MST). So far nothing depended on this, however the next patch will depend on link_trained==false for changing the LTTPR mode to non-transparent. Cc: # v5.15+ Cc: Ville Syrjälä Reviewed-by: Ankit Nautiyal Signed-off-by: Imre Deak Link: https://patchwork.freedesktop.org/patch/msgid/20240708190029.271247-2-imre.deak@intel.com (cherry picked from commit a4d5ce61765c08ab364aa4b327f6739b646e6cfa) Signed-off-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/display/intel_dp.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 3903f6ead6e6..59f11af3b0a1 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -5314,6 +5314,8 @@ static int intel_dp_retrain_link(struct intel_encoder *encoder, const struct intel_crtc_state *crtc_state = to_intel_crtc_state(crtc->base.state); + intel_dp->link_trained = false; + intel_dp_check_frl_training(intel_dp); intel_dp_pcon_dsc_configure(intel_dp, crtc_state); intel_dp_start_link_train(NULL, intel_dp, crtc_state); -- cgit v1.2.3 From 509580fad7323b6a5da27e8365cd488f3b57210e Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Mon, 8 Jul 2024 22:00:25 +0300 Subject: drm/i915/dp: Don't switch the LTTPR mode on an active link MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Switching to transparent mode leads to a loss of link synchronization, so prevent doing this on an active link. This happened at least on an Intel N100 system / DELL UD22 dock, the LTTPR residing either on the host or the dock. To fix the issue, keep the current mode on an active link, adjusting the LTTPR count accordingly (resetting it to 0 in transparent mode). v2: Adjust code comment during link training about reiniting the LTTPRs. (Ville) Fixes: 7b2a4ab8b0ef ("drm/i915: Switch to LTTPR transparent mode link training") Reported-and-tested-by: Gareth Yu Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/10902 Cc: # v5.15+ Cc: Ville Syrjälä Reviewed-by: Ville Syrjälä Reviewed-by: Ankit Nautiyal Signed-off-by: Imre Deak Link: https://patchwork.freedesktop.org/patch/msgid/20240708190029.271247-3-imre.deak@intel.com (cherry picked from commit 211ad49cf8ccfdc798a719b4d1e000d0a8a9e588) Signed-off-by: Tvrtko Ursulin --- .../gpu/drm/i915/display/intel_dp_link_training.c | 55 +++++++++++++++++++--- 1 file changed, 48 insertions(+), 7 deletions(-) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c index 1bc4ef84ff3b..d044c8e36bb3 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -117,10 +117,24 @@ intel_dp_set_lttpr_transparent_mode(struct intel_dp *intel_dp, bool enable) return drm_dp_dpcd_write(&intel_dp->aux, DP_PHY_REPEATER_MODE, &val, 1) == 1; } -static int intel_dp_init_lttpr(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEIVER_CAP_SIZE]) +static bool intel_dp_lttpr_transparent_mode_enabled(struct intel_dp *intel_dp) +{ + return intel_dp->lttpr_common_caps[DP_PHY_REPEATER_MODE - + DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV] == + DP_PHY_REPEATER_MODE_TRANSPARENT; +} + +/* + * Read the LTTPR common capabilities and switch the LTTPR PHYs to + * non-transparent mode if this is supported. Preserve the + * transparent/non-transparent mode on an active link. + * + * Return the number of detected LTTPRs in non-transparent mode or 0 if the + * LTTPRs are in transparent mode or the detection failed. + */ +static int intel_dp_init_lttpr_phys(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { int lttpr_count; - int i; if (!intel_dp_read_lttpr_common_caps(intel_dp, dpcd)) return 0; @@ -134,6 +148,19 @@ static int intel_dp_init_lttpr(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEI if (lttpr_count == 0) return 0; + /* + * Don't change the mode on an active link, to prevent a loss of link + * synchronization. See DP Standard v2.0 3.6.7. about the LTTPR + * resetting its internal state when the mode is changed from + * non-transparent to transparent. + */ + if (intel_dp->link_trained) { + if (lttpr_count < 0 || intel_dp_lttpr_transparent_mode_enabled(intel_dp)) + goto out_reset_lttpr_count; + + return lttpr_count; + } + /* * See DP Standard v2.0 3.6.6.1. about the explicit disabling of * non-transparent mode and the disable->enable non-transparent mode @@ -154,11 +181,25 @@ static int intel_dp_init_lttpr(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEI "Switching to LTTPR non-transparent LT mode failed, fall-back to transparent mode\n"); intel_dp_set_lttpr_transparent_mode(intel_dp, true); - intel_dp_reset_lttpr_count(intel_dp); - return 0; + goto out_reset_lttpr_count; } + return lttpr_count; + +out_reset_lttpr_count: + intel_dp_reset_lttpr_count(intel_dp); + + return 0; +} + +static int intel_dp_init_lttpr(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEIVER_CAP_SIZE]) +{ + int lttpr_count; + int i; + + lttpr_count = intel_dp_init_lttpr_phys(intel_dp, dpcd); + for (i = 0; i < lttpr_count; i++) intel_dp_read_lttpr_phy_caps(intel_dp, dpcd, DP_PHY_LTTPR(i)); @@ -1482,10 +1523,10 @@ void intel_dp_start_link_train(struct intel_atomic_state *state, struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp); struct intel_encoder *encoder = &dig_port->base; bool passed; - /* - * TODO: Reiniting LTTPRs here won't be needed once proper connector - * HW state readout is added. + * Reinit the LTTPRs here to ensure that they are switched to + * non-transparent mode. During an earlier LTTPR detection this + * could've been prevented by an active link. */ int lttpr_count = intel_dp_init_lttpr_and_dprx_caps(intel_dp); -- cgit v1.2.3