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drm/amd/display: Implement DDC probe over AUX channel

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DDC probe means that we use the DDC (Display Data Channel) to
verify whether a display is connected or not.

This was written with mainly analog connectors in mind, so it
didn't work over the AUX channel. However, in order to support
external DP bridge encoders found in CIK APUs, it needs to work
over the AUX channel too.

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 22:08:30 +01:00 committed by Alex Deucher
parent ee5c4855f4
commit 7b6e66b6dd
1 changed files with 9 additions and 2 deletions
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11
drivers/gpu/drm/amd/display/dc/link/link_detection.c
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@ -903,11 +903,18 @@ static bool link_detect_evaluate_edid_header(uint8_t edid_header[8])
*/
static bool link_detect_ddc_probe(struct dc_link *link)
{
enum signal_type signal = link_detect_sink_signal_type(link, DETECT_REASON_HPD);
enum ddc_transaction_type transaction_type = get_ddc_transaction_type(signal);
uint8_t edid_header[8] = {0};
uint8_t zero = 0;
bool ddc_probed;
if (!link->ddc)
return false;
uint8_t edid_header[8] = {0};
bool ddc_probed = i2c_read(link->ddc, 0x50, edid_header, sizeof(edid_header));
set_ddc_transaction_type(link->ddc, transaction_type);
ddc_probed = link_query_ddc_data(link->ddc, 0x50, &zero, 1, edid_header, sizeof(edid_header));
if (!ddc_probed)
return false;