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drm/dp: Add drm_dp_downstream_mode()

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The downstream facing port caps in the DPCD can give us a hint
as to what kind of display mode the sink can use if it doesn't
have an EDID. Use that information to pick a suitable mode.

v2: Use Returns: for kdoc (Lyude)
    Add kdocs for drm_display_mode_from_cea_vic() (Lyude)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200904115354.25336-14-ville.syrjala@linux.intel.com
Reviewed-by: Lyude Paul <lyude@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Ville Syrjälä
2020-09-04 14:53:49 +03:00
parent b7feffd584
commit 7af655bce2
4 changed files with 98 additions and 0 deletions
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54
drivers/gpu/drm/drm_dp_helper.c
View File

@@ -808,6 +808,60 @@ int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
}
EXPORT_SYMBOL(drm_dp_downstream_max_bpc);
/**
* drm_dp_downstream_mode() - return a mode for downstream facing port
* @dpcd: DisplayPort configuration data
* @port_cap: port capabilities
*
* Provides a suitable mode for downstream facing ports without EDID.
*
* Returns: A new drm_display_mode on success or NULL on failure
*/
struct drm_display_mode *
drm_dp_downstream_mode(struct drm_device *dev,
const u8 dpcd[DP_RECEIVER_CAP_SIZE],
const u8 port_cap[4])
{
u8 vic;
if (!drm_dp_is_branch(dpcd))
return NULL;
if (dpcd[DP_DPCD_REV] < 0x11)
return NULL;
switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
case DP_DS_PORT_TYPE_NON_EDID:
switch (port_cap[0] & DP_DS_NON_EDID_MASK) {
case DP_DS_NON_EDID_720x480i_60:
vic = 6;
break;
case DP_DS_NON_EDID_720x480i_50:
vic = 21;
break;
case DP_DS_NON_EDID_1920x1080i_60:
vic = 5;
break;
case DP_DS_NON_EDID_1920x1080i_50:
vic = 20;
break;
case DP_DS_NON_EDID_1280x720_60:
vic = 4;
break;
case DP_DS_NON_EDID_1280x720_50:
vic = 19;
break;
default:
return NULL;
}
return drm_display_mode_from_cea_vic(dev, vic);
default:
return NULL;
}
}
EXPORT_SYMBOL(drm_dp_downstream_mode);
/**
* drm_dp_downstream_id() - identify branch device
* @aux: DisplayPort AUX channel