From c474420ba412280bc49888c3ce224f0c650c0dcb Mon Sep 17 00:00:00 2001 From: Jani Nikula Date: Thu, 7 Oct 2021 13:57:27 +0300 Subject: [PATCH] drm/i915/dp: take LTTPR into account in 128b/132b rates MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Limit the supported UHBR rates based on the repeater support, if there are repeaters. This should be done in DP helper level, but that requires an overhaul of the LTTPR handling, as the max rate is not enough to represent how 128b/132b rates may be masked along the way. Curiously, the spec says: * Shall be cleared to 00h when operating in 8b/10b Link Layer. * Each LTTPR on the way back to the DPTX shall clear the bits that do not correspond to the LTTPR's current bit rate. It's rather vague if we can reliably use the field at this time due to the wording "operating" and "current". But it would seem bizarre to have to wait until trying to operate a 128b/132b link layer at a certain bit rate to figure this out. Cc: Ville Syrjälä Reviewed-by: Ville Syrjälä Signed-off-by: Jani Nikula Link: https://patchwork.freedesktop.org/patch/msgid/20211007105727.18439-1-jani.nikula@intel.com --- drivers/gpu/drm/i915/display/intel_dp.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 74a657a..f6b26ce 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -140,6 +140,9 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp) return; } + /* + * Sink rates for 8b/10b. + */ max_rate = drm_dp_bw_code_to_link_rate(intel_dp->dpcd[DP_MAX_LINK_RATE]); max_lttpr_rate = drm_dp_lttpr_max_link_rate(intel_dp->lttpr_common_caps); if (max_lttpr_rate) @@ -163,6 +166,21 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp) drm_dp_dpcd_readb(&intel_dp->aux, DP_128B132B_SUPPORTED_LINK_RATES, &uhbr_rates); + if (drm_dp_lttpr_count(intel_dp->lttpr_common_caps)) { + /* We have a repeater */ + if (intel_dp->lttpr_common_caps[0] >= 0x20 && + intel_dp->lttpr_common_caps[DP_MAIN_LINK_CHANNEL_CODING_PHY_REPEATER - + DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV] & + DP_PHY_REPEATER_128B132B_SUPPORTED) { + /* Repeater supports 128b/132b, valid UHBR rates */ + uhbr_rates &= intel_dp->lttpr_common_caps[DP_PHY_REPEATER_128B132B_RATES - + DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV]; + } else { + /* Does not support 128b/132b */ + uhbr_rates = 0; + } + } + if (uhbr_rates & DP_UHBR10) intel_dp->sink_rates[i++] = 1000000; if (uhbr_rates & DP_UHBR13_5) -- 2.7.4