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drm/amd/display: Read LTTPR ALPM caps during link cap retrieval

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[Why]
The latest DP spec requires the DP TX to read DPCD F0000h through F0009h
when detecting LTTPR capabilities for the first time.

[How]
Update LTTPR cap retrieval to read up to F0009h (two more bytes than the
previous F0007h), and store the LTTPR ALPM capabilities.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
George Shen
2025-02-04 14:34:02 -05:00
committed by Alex Deucher
parent 5f7e384ab5
commit de84d58012
2 changed files with 17 additions and 1 deletions
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6
drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
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@@ -1502,7 +1502,7 @@ static bool dpcd_read_sink_ext_caps(struct dc_link *link)
enum dc_status dp_retrieve_lttpr_cap(struct dc_link *link)
{
uint8_t lttpr_dpcd_data[8] = {0};
uint8_t lttpr_dpcd_data[10] = {0};
enum dc_status status;
bool is_lttpr_present;
@@ -1552,6 +1552,10 @@ enum dc_status 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];
link->dpcd_caps.lttpr_caps.alpm.raw =
lttpr_dpcd_data[DP_LTTPR_ALPM_CAPABILITIES -
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 & AMD_EXT_DISPLAY_PATH_CAPS__EXT_CHIP_MASK) == AMD_EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN) &&