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| author | Michael Strauss <michael.strauss@amd.com> | 2022-08-31 15:10:43 -0400 |
|---|---|---|
| committer | Alex Deucher <alexander.deucher@amd.com> | 2022-09-21 17:19:25 -0400 |
| commit | 29956d0fded036a570bd8e7d4ea4b1a1730307d2 (patch) | |
| tree | 20a3fd88716ae0c3ceb729ffc93673da2555c069 /drivers | |
| parent | cb0eca01ad9756e853efec3301203c2b5b45aa9f (diff) | |
| download | linux-stable-29956d0fded036a570bd8e7d4ea4b1a1730307d2.tar.gz linux-stable-29956d0fded036a570bd8e7d4ea4b1a1730307d2.tar.bz2 linux-stable-29956d0fded036a570bd8e7d4ea4b1a1730307d2.zip | |
drm/amd/display: Assume an LTTPR is always present on fixed_vs links
[WHY]
LTTPRs can in very rare instsances fail to increment DPCD LTTPR count.
This results in aux-i LTTPR requests to be sent to the wrong DPCD
address, which causes link training failure.
[HOW]
Override internal repeater count if fixed_vs flag is set for a given link
Reviewed-by: George Shen <George.Shen@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Michael Strauss <michael.strauss@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c index 48dad093ae8b..5f8ef18e3e27 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c @@ -5121,6 +5121,14 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link) lttpr_dpcd_data[DP_PHY_REPEATER_128B132B_RATES - DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV]; + /* If this chip cap is set, at least one retimer must exist in the chain + * Override count to 1 if we receive a known bad count (0 or an invalid value) */ + if (link->chip_caps & EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN && + (dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt) == 0)) { + ASSERT(0); + link->dpcd_caps.lttpr_caps.phy_repeater_cnt = 0x80; + } + /* Attempt to train in LTTPR transparent mode if repeater count exceeds 8. */ is_lttpr_present = (link->dpcd_caps.lttpr_caps.max_lane_count > 0 && link->dpcd_caps.lttpr_caps.max_lane_count <= 4 && |