From: Michael Strauss <michael.stra...@amd.com>
[ Upstream commit 4f01a68751194d05280d659a65758c09e4af04d6 ]
[WHY]
Currently the absence of UHBR cable ID caps from USB-C PD does not block UHBR
rates. In situations where DPCD reports valid UHBR capability but USB-C PD
does not, such as using a USB-C to DP1.4 dongle connected to a native DP2.1
cable, link loss and lightup failures can be seen as a result.
Additionally, in edge cases where a platform supports cable ID but DMUB
doesn't correctly return cable ID caps, driver currently also allows UHBR.
[HOW]
Block UHBR rates over DP alt mode if cable id indicates no UHBR support.
Additionally, block UHBR rates if a cable ID supported platform receives no
reply from a DMUB cable id query.
Reviewed-by: Wenjing Liu <wenjing....@amd.com>
Reviewed-by: Ovidiu Bunea <ovidiu.bu...@amd.com>
Signed-off-by: Michael Strauss <michael.stra...@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pil...@amd.com>
Tested-by: Daniel Wheeler <daniel.whee...@amd.com>
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
.../dc/link/protocols/link_dp_capability.c | 22 ++++++++++++++-----
1 file changed, 16 insertions(+), 6 deletions(-)
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 60015e94c4aa8..ae6d7e3d117e2 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
@@ -1402,7 +1402,8 @@ static bool get_usbc_cable_id(struct dc_link *link, union
dp_cable_id *cable_id)
if (!link->ctx->dmub_srv ||
link->ep_type != DISPLAY_ENDPOINT_PHY ||
- link->link_enc->features.flags.bits.DP_IS_USB_C == 0)
+ link->link_enc->features.flags.bits.DP_IS_USB_C == 0 ||
+ link->link_enc->features.flags.bits.IS_DP2_CAPABLE == 0)
return false;
memset(&cmd, 0, sizeof(cmd));
@@ -1415,7 +1416,9 @@ static bool get_usbc_cable_id(struct dc_link *link, union
dp_cable_id *cable_id)
cable_id->raw = cmd.cable_id.data.output_raw;
DC_LOG_DC("usbc_cable_id = %d.\n", cable_id->raw);
}
- return cmd.cable_id.header.ret_status == 1;
+
+ ASSERT(cmd.cable_id.header.ret_status);
+ return true;
}
static void retrieve_cable_id(struct dc_link *link)
@@ -2087,6 +2090,8 @@ struct dc_link_settings dp_get_max_link_cap(struct
dc_link *link)
/* get max link encoder capability */
if (link_enc)
link_enc->funcs->get_max_link_cap(link_enc, &max_link_cap);
+ else
+ return max_link_cap;
/* Lower link settings based on sink's link cap */
if (link->reported_link_cap.lane_count < max_link_cap.lane_count)
@@ -2120,10 +2125,15 @@ struct dc_link_settings dp_get_max_link_cap(struct
dc_link *link)
*/
cable_max_link_rate = get_cable_max_link_rate(link);
- if (!link->dc->debug.ignore_cable_id &&
- cable_max_link_rate != LINK_RATE_UNKNOWN) {
- if (cable_max_link_rate < max_link_cap.link_rate)
- max_link_cap.link_rate = cable_max_link_rate;
+ if (!link->dc->debug.ignore_cable_id) {
+ if (cable_max_link_rate != LINK_RATE_UNKNOWN)
+ // cable max link rate known
+ max_link_cap.link_rate = MIN(max_link_cap.link_rate,
cable_max_link_rate);
+ else if (link_enc->funcs->is_in_alt_mode &&
link_enc->funcs->is_in_alt_mode(link_enc))
+ // cable max link rate ambiguous, DP alt mode, limit to
HBR3
+ max_link_cap.link_rate = MIN(max_link_cap.link_rate,
LINK_RATE_HIGH3);
+ //else {}
+ // cable max link rate ambiguous, DP, do nothing
if (!link->dpcd_caps.cable_id.bits.UHBR13_5_CAPABILITY &&
link->dpcd_caps.cable_id.bits.CABLE_TYPE >= 2)
--
2.43.0
