The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 0dd1190faff7f7b389291266e118deb381b6c8d9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024081207-voter-silencer-8387@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

0dd1190faff7 ("drm/amd/display: Fix reduced resolution and refresh rate") 82c421ba46ec ("drm/amd/display: Add fallback defaults for invalid LTTPR DPCD caps") 4eaf110f97ae ("drm/amd/display: Check UHBR13.5 cap when determining max link cap")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0dd1190faff7f7b389291266e118deb381b6c8d9 Mon Sep 17 00:00:00 2001 From: Daniel Sa daniel.sa@amd.com Date: Thu, 13 Jun 2024 15:38:06 -0400 Subject: [PATCH] drm/amd/display: Fix reduced resolution and refresh rate

[WHY] Some monitors are forced to a lower resolution and refresh rate after system restarts.

[HOW] Some monitors may give invalid LTTPR information when queried such as indicating they have one DP lane instead of 4. If given an invalid DPCD version, skip over getting lttpr link rate and lane counts.

Reviewed-by: Wenjing Liu wenjing.liu@amd.com Cc: Mario Limonciello mario.limonciello@amd.com Cc: Alex Deucher alexander.deucher@amd.com Cc: stable@vger.kernel.org Signed-off-by: Alex Hung alex.hung@amd.com Signed-off-by: Daniel Sa daniel.sa@amd.com Tested-by: Daniel Wheeler daniel.wheeler@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c index f1cac74dd7f7..46bb7a855bc2 100644 --- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c +++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c @@ -409,9 +409,6 @@ static enum dc_link_rate get_lttpr_max_link_rate(struct dc_link *link) case LINK_RATE_HIGH3: lttpr_max_link_rate = link->dpcd_caps.lttpr_caps.max_link_rate; break; - default: - // Assume all LTTPRs support up to HBR3 to improve misbehaving sink interop - lttpr_max_link_rate = LINK_RATE_HIGH3; }

if (link->dpcd_caps.lttpr_caps.supported_128b_132b_rates.bits.UHBR20) @@ -2137,15 +2134,19 @@ struct dc_link_settings dp_get_max_link_cap(struct dc_link *link) * notes: repeaters do not snoop in the DPRX Capabilities addresses (3.6.3). */ if (dp_is_lttpr_present(link)) { - if (link->dpcd_caps.lttpr_caps.max_lane_count < max_link_cap.lane_count) - max_link_cap.lane_count = link->dpcd_caps.lttpr_caps.max_lane_count; - lttpr_max_link_rate = get_lttpr_max_link_rate(link);

- if (lttpr_max_link_rate < max_link_cap.link_rate) - max_link_cap.link_rate = lttpr_max_link_rate; + /* Some LTTPR devices do not report valid DPCD revisions, if so, do not take it's link cap into consideration. */ + if (link->dpcd_caps.lttpr_caps.revision.raw >= DPCD_REV_14) { + if (link->dpcd_caps.lttpr_caps.max_lane_count < max_link_cap.lane_count) + max_link_cap.lane_count = link->dpcd_caps.lttpr_caps.max_lane_count; + lttpr_max_link_rate = get_lttpr_max_link_rate(link);

- if (!link->dpcd_caps.lttpr_caps.supported_128b_132b_rates.bits.UHBR13_5) - is_uhbr13_5_supported = false; + if (lttpr_max_link_rate < max_link_cap.link_rate) + max_link_cap.link_rate = lttpr_max_link_rate; + + if (!link->dpcd_caps.lttpr_caps.supported_128b_132b_rates.bits.UHBR13_5) + is_uhbr13_5_supported = false; + }

DC_LOG_HW_LINK_TRAINING("%s\n Training with LTTPR, max_lane count %d max_link rate %d \n", __func__,