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drm/amd/display: Link detection for external DP bridge encoders

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Deal with some minor idiosyncracies of TRAVIS and NUTMEG chips.

- Always use DP signal type with these chips so that the
  normal DP code paths can work with them without a major
  refactor of the code base. Properly set this.

- NUTMEG seems to only work with HBR, not RBR, so set a
  preferred link rate for this chip.
  See amdgpu_atombios_dp_get_dp_link_config() for reference.

- NUTMEG is recognized as a DP branch device but reports 0 sinks,
  which is wrong and confuses DC (it hits an early return).
  Fix that by hardcoding the sink count to 1.

- Fixup old DC code selecting a special panel mode necessary
  for NUTMEG and TRAVIS.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Timur Kristóf 2026-01-26 22:08:34 +01:00 committed by Alex Deucher
parent 9f556ac2e3
commit d740af07a7
2 changed files with 14 additions and 14 deletions
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20
drivers/gpu/drm/amd/display/dc/link/link_detection.c
View File

@ -150,14 +150,6 @@ static enum signal_type get_basic_signal_type(struct graphics_object_id encoder,
default:
return SIGNAL_TYPE_NONE;
}
} else if (downstream.type == OBJECT_TYPE_ENCODER) {
switch (downstream.id) {
case ENCODER_ID_EXTERNAL_NUTMEG:
case ENCODER_ID_EXTERNAL_TRAVIS:
return SIGNAL_TYPE_DISPLAY_PORT;
default:
return SIGNAL_TYPE_NONE;
}
}
return SIGNAL_TYPE_NONE;
@ -174,6 +166,10 @@ static enum signal_type link_detect_sink_signal_type(struct dc_link *link,
struct audio_support *aud_support;
struct graphics_object_id enc_id;
/* External DP bridges should use DP signal regardless of connector type. */
if (link->ext_enc_id.id)
return SIGNAL_TYPE_DISPLAY_PORT;
if (link->is_dig_mapping_flexible)
enc_id = (struct graphics_object_id){.id = ENCODER_ID_UNKNOWN};
else
@ -620,6 +616,14 @@ static bool detect_dp(struct dc_link *link,
link->dpcd_caps.usb4_dp_tun_info.dp_tun_cap.raw = 0;
}
if (link->ext_enc_id.id) {
/* Fix number of connected sinks reported by external DP bridge */
link->dpcd_caps.sink_count.bits.SINK_COUNT = 1;
/* NUTMEG requires that we use HBR, doesn't work with RBR. */
if (link->dpcd_caps.branch_dev_id == DP_BRANCH_DEVICE_ID_00001A)
link->preferred_link_setting.link_rate = LINK_RATE_HIGH;
}
return true;
}

8
drivers/gpu/drm/amd/display/dc/link/protocols/link_edp_panel_control.c
View File

@ -100,11 +100,7 @@ void dp_set_panel_mode(struct dc_link *link, enum dp_panel_mode panel_mode)
enum dp_panel_mode dp_get_panel_mode(struct dc_link *link)
{
/* We need to explicitly check that connector
* is not DP. Some Travis_VGA get reported
* by video bios as DP.
*/
if (link->connector_signal != SIGNAL_TYPE_DISPLAY_PORT) {
if (link->ext_enc_id.id) {
switch (link->dpcd_caps.branch_dev_id) {
case DP_BRANCH_DEVICE_ID_0022B9:
@ -124,7 +120,7 @@ enum dp_panel_mode dp_get_panel_mode(struct dc_link *link)
}
break;
case DP_BRANCH_DEVICE_ID_00001A:
/* alternate scrambler reset is required for Travis
/* alternate scrambler reset is required for NUTMEG
* for the case when external chip does not provide
* sink device id, alternate scrambler scheme will
* be overriden later by querying Encoder feature