From eddbb074ce6a3af5fe1d9c546e5d474ca9fa799d Mon Sep 17 00:00:00 2001 From: Imre Deak Date: Sat, 9 Apr 2022 01:46:29 +0300 Subject: [PATCH] drm/i915/dp: Add workaround for spurious AUX timeouts/hotplugs on LTTPR links To avoid AUX timeouts and subsequent spurious hotplug interrupts, make sure that the first DPCD access during detection is a read from an LTTPR register. Some ADLP DP link configuration at least with multiple LTTPRs expects the first DPCD access during the LTTPR/DPCD detection after hotplug to be a read from the LTTPR range starting with DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV. The side effect of this read is to put each LTTPR into the LTTPR transparent or LTTPR non-transparent mode. The lack of the above read may leave some of the LTTPRs in non-LTTPR mode, while other LTTPRs in LTTPR transparent or LTTPR non-transparent mode (for instance LTTPRs after system suspend/resume that kept their mode from before suspend). Due to the different AUX timeouts the different modes imply, the DPCD access from a non-LTTPR range will timeout and lead to an LTTPR generated hotplug towards the source (which the LTTPR firmware uses to account for buggy TypeC adapters with a long wake-up delay). SYSCROS: 72939 v2: Keep DPCD read-out working on non-LTTPR platforms. v3: Summarize what and why the patch does at the beginning of the commit log. (Jani) Signed-off-by: Imre Deak Reviewed-by: Jani Nikula Link: https://patchwork.freedesktop.org/patch/msgid/20220408224629.845887-1-imre.deak@intel.com --- .../gpu/drm/i915/display/intel_dp_link_training.c | 33 +++++++++++----------- 1 file changed, 17 insertions(+), 16 deletions(-) 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 26f9e2b748e4..9feaf1a589f3 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -82,19 +82,8 @@ static bool intel_dp_read_lttpr_common_caps(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEIVER_CAP_SIZE]) { struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base; - struct drm_i915_private *i915 = to_i915(encoder->base.dev); int ret; - if (intel_dp_is_edp(intel_dp)) - return false; - - /* - * Detecting LTTPRs must be avoided on platforms with an AUX timeout - * period < 3.2ms. (see DP Standard v2.0, 2.11.2, 3.6.6.1). - */ - if (DISPLAY_VER(i915) < 10 || IS_GEMINILAKE(i915)) - return false; - ret = drm_dp_read_lttpr_common_caps(&intel_dp->aux, dpcd, intel_dp->lttpr_common_caps); if (ret < 0) @@ -197,13 +186,25 @@ static int intel_dp_init_lttpr(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEI */ int intel_dp_init_lttpr_and_dprx_caps(struct intel_dp *intel_dp) { - u8 dpcd[DP_RECEIVER_CAP_SIZE]; - int lttpr_count; + struct drm_i915_private *i915 = dp_to_i915(intel_dp); + int lttpr_count = 0; - if (drm_dp_read_dpcd_caps(&intel_dp->aux, dpcd)) - return -EIO; + /* + * Detecting LTTPRs must be avoided on platforms with an AUX timeout + * period < 3.2ms. (see DP Standard v2.0, 2.11.2, 3.6.6.1). + */ + if (!intel_dp_is_edp(intel_dp) && + (DISPLAY_VER(i915) >= 10 && !IS_GEMINILAKE(i915))) { + u8 dpcd[DP_RECEIVER_CAP_SIZE]; + + if (drm_dp_dpcd_probe(&intel_dp->aux, DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV)) + return -EIO; - lttpr_count = intel_dp_init_lttpr(intel_dp, dpcd); + if (drm_dp_read_dpcd_caps(&intel_dp->aux, dpcd)) + return -EIO; + + lttpr_count = intel_dp_init_lttpr(intel_dp, dpcd); + } /* * The DPTX shall read the DPRX caps after LTTPR detection, so re-read -- 2.11.0