diff options
| -rw-r--r-- | drivers/gpu/drm/drm_dp_helper.c | 33 | ||||
| -rw-r--r-- | include/drm/drm_dp_helper.h | 2 |
2 files changed, 35 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 5d20255f3db3..f171fbf8b1b9 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -438,6 +438,39 @@ int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link) } EXPORT_SYMBOL(drm_dp_link_configure); +/** + * drm_dp_downstream_max_clock() - extract branch device max + * pixel rate for legacy VGA + * converter or max TMDS clock + * rate for others + * @dpcd: DisplayPort configuration data + * @port_cap: port capabilities + * + * Returns max clock in kHz on success or 0 if max clock not defined + */ +int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE], + const u8 port_cap[4]) +{ + int type = port_cap[0] & DP_DS_PORT_TYPE_MASK; + bool detailed_cap_info = dpcd[DP_DOWNSTREAMPORT_PRESENT] & + DP_DETAILED_CAP_INFO_AVAILABLE; + + if (!detailed_cap_info) + return 0; + + switch (type) { + case DP_DS_PORT_TYPE_VGA: + return port_cap[1] * 8 * 1000; + case DP_DS_PORT_TYPE_DVI: + case DP_DS_PORT_TYPE_HDMI: + case DP_DS_PORT_TYPE_DP_DUALMODE: + return port_cap[1] * 2500; + default: + return 0; + } +} +EXPORT_SYMBOL(drm_dp_downstream_max_clock); + /* * I2C-over-AUX implementation */ diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 0d84046a1ed6..60dd9dca4ce2 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -815,6 +815,8 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link); +int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE], + const u8 port_cap[4]); void drm_dp_aux_init(struct drm_dp_aux *aux); int drm_dp_aux_register(struct drm_dp_aux *aux); |