[PATCH v22 02/38] usb: host: xhci: Repurpose event handler for skipping interrupter events

[Wesley Cheng <quic_wcheng@quicinc.com>]

Depending on the interrupter use case, the OS may only be used to handle
the interrupter event ring clean up.  In these scenarios, event TRBs don't
need to be handled by the OS, so introduce an xhci interrupter flag to tag
if the events from an interrupter needs to be handled or not.

Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
---
 drivers/usb/host/xhci-ring.c | 17 +++++++++++++----
 drivers/usb/host/xhci.h      |  1 +
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9e90d2952760..80dca780317a 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2951,14 +2951,22 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 }
 
 /*
- * This function handles one OS-owned event on the event ring. It may drop
- * xhci->lock between event processing (e.g. to pass up port status changes).
+ * This function handles one OS-owned event on the event ring, or ignores one event
+ * on interrupters which are non-OS owned. It may drop xhci->lock between event
+ * processing (e.g. to pass up port status changes).
  */
 static int xhci_handle_event_trb(struct xhci_hcd *xhci, struct xhci_interrupter *ir,
 				 union xhci_trb *event)
 {
 	u32 trb_type;
 
+	/*
+	 * Some interrupters do not need to handle event TRBs, as they may be
+	 * managed by another entity, but rely on the OS to clean up.
+	 */
+	if (ir->skip_events)
+		return 0;
+
 	trace_xhci_handle_event(ir->event_ring, &event->generic);
 
 	/*
@@ -3047,8 +3055,9 @@ static void xhci_clear_interrupt_pending(struct xhci_hcd *xhci,
 }
 
 /*
- * Handle all OS-owned events on an interrupter event ring. It may drop
- * and reaquire xhci->lock between event processing.
+ * Handle all OS-owned events on an interrupter event ring, or skip pending events
+ * for non OS owned interrupter event ring. It may drop and reaquire xhci->lock
+ * between event processing.
  */
 static int xhci_handle_events(struct xhci_hcd *xhci, struct xhci_interrupter *ir)
 {
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 1c6126ed55b0..efbd1f651da4 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1430,6 +1430,7 @@ struct xhci_interrupter {
 	struct xhci_intr_reg __iomem *ir_set;
 	unsigned int		intr_num;
 	bool			ip_autoclear;
+	bool			skip_events;
 	u32			isoc_bei_interval;
 	/* For interrupter registers save and restore over suspend/resume */
 	u32	s3_irq_pending;