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drm: apple: dcp-fabric: give an idle port's pipeline to a waiting display #357

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drm: apple: dcp-fabric: give an idle port's pipeline to a waiting display #357

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49 changes: 49 additions & 0 deletions drivers/gpu/drm/apple/dcp-fabric.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1378,6 +1378,52 @@ static int dcp_typec_port_busy(struct apple_dcp_typec_port *port,
return -ENOSPC;
}

/*
* @waiting has a display (HPD up) but no pipeline. A direct DP-alt port that
* holds one of @waiting's pipelines with no display behind it (its sink has
* never asserted HPD, as a USB-C hub with a DP output and nothing plugged in)
* gives it up: a pipeline goes to a display, not to whichever port entered DP
* mode first. The idle port keeps DP mode and is routed again when a pipeline
* is free and its own sink asserts HPD. Returns true if one was released.
*/
static bool dcp_typec_reclaim_idle(struct apple_dcp_typec_port *waiting)
{
struct apple_dcp_typec_route *route;
struct apple_dcp_typec_port *idle;

lockdep_assert_held(&dcp_typec_fabric_lock);

list_for_each_entry(route, &waiting->routes, port_link) {
list_for_each_entry(idle, &dcp_typec_ports, link) {
struct apple_dcp_typec_route *owner = idle->owner;
struct apple_dcp *dcp;
const char *from = NULL, *to = NULL;

if (idle == waiting || !owner || owner->tunnel ||
owner->dcp != route->dcp || idle->safe_pending ||
idle->dp_hpd || idle->hpd)
continue;
dcp = owner->dcp;
if (dcp->typec_cable_connected ||
(dcp->typec_connector &&
READ_ONCE(dcp->typec_connector->connected)))
continue;
if (dcp_typec_route_deactivate(owner))
return false;
idle->preferred_route = owner;
idle->owner = NULL;
idle->busy_noted = false;
of_property_read_string(idle->connector_np, "label", &from);
of_property_read_string(waiting->connector_np, "label", &to);
dev_info(dcp->dev,
"external display pipeline moves from %s (no display) to the display on %s\n",
from ?: "a USB-C port", to ?: "a USB-C port");
return true;
}
}
return false;
}

static int dcp_typec_route_set(struct typec_mux_dev *mux,
struct typec_mux_state *state)
{
Expand Down Expand Up @@ -1519,6 +1565,9 @@ static int dcp_typec_route_set(struct typec_mux_dev *mux,

if (!port->owner) {
best = dcp_typec_free_route(port);
/* A pipeline held by a port with no display goes to this one. */
if (!best && hpd && dcp_typec_reclaim_idle(port))
best = dcp_typec_free_route(port);
/* Every pipeline is driving another port's display. */
if (!best)
return hpd ? dcp_typec_port_busy(port, route->dcp) : -ENOSPC;
Expand Down