usb: host: xhci-mem: Cleanup pending secondary event ring events

JIRA: https://issues.redhat.com/browse/RHEL-116016
Conflicts:
* Commit bea5892 ("xhci: Limit time spent with xHC interrupts
  disabled during bus resume") causes a conflicts here by making
  xhci_enable_interrupter() and xhci_disable_interrupter() public
  on drivers/usb/host/xhci.h

commit 5beb4a5
Author: Wesley Cheng <quic_wcheng@quicinc.com>
Date: Wed, 9 Apr 2025 12:47:35 -0700

  As part of xHCI bus suspend, the xHCI is halted.  However, if there are
  pending events in the secondary event ring, it is observed that the xHCI
  controller stops responding to further commands upon host or device
  initiated bus resume.  Iterate through all pending events and update the
  dequeue pointer to the beginning of the event ring.

  Tested-by: Puma Hsu <pumahsu@google.com>
  Tested-by: Daehwan Jung <dh10.jung@samsung.com>
  Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
  Acked-by: Mark Brown <broonie@kernel.org>
  Link: https://lore.kernel.org/r/20250409194804.3773260-3-quic_wcheng@quicinc.com
  Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Desnes Nunes <desnesn@redhat.com>

Author: Desnes Nunes

drivers/usb/host/xhci-mem.c

@@ -1805,7 +1805,7 @@ xhci_remove_interrupter(struct xhci_hcd *xhci, struct xhci_interrupter *ir)
 		tmp &= ERST_SIZE_MASK;
 		writel(tmp, &ir->ir_set->erst_size);
 
-		xhci_write_64(xhci, ERST_EHB, &ir->ir_set->erst_dequeue);
+		xhci_update_erst_dequeue(xhci, ir, true);
 	}
 }
 
@@ -1848,6 +1848,11 @@ void xhci_remove_secondary_interrupter(struct usb_hcd *hcd, struct xhci_interrup
 		return;
 	}
 
+	/*
+	 * Cleanup secondary interrupter to ensure there are no pending events.
+	 * This also updates event ring dequeue pointer back to the start.
+	 */
+	xhci_skip_sec_intr_events(xhci, ir->event_ring, ir);
 	intr_num = ir->intr_num;
 
 	xhci_remove_interrupter(xhci, ir);

drivers/usb/host/xhci-ring.c

@@ -3050,9 +3050,9 @@ static int xhci_handle_event_trb(struct xhci_hcd *xhci, struct xhci_interrupter
  * - When all events have finished
  * - To avoid "Event Ring Full Error" condition
  */
-static void xhci_update_erst_dequeue(struct xhci_hcd *xhci,
-				     struct xhci_interrupter *ir,
-				     bool clear_ehb)
+void xhci_update_erst_dequeue(struct xhci_hcd *xhci,
+			      struct xhci_interrupter *ir,
+			      bool clear_ehb)
 {
 	u64 temp_64;
 	dma_addr_t deq;
@@ -3095,10 +3095,11 @@ static void xhci_clear_interrupt_pending(struct xhci_interrupter *ir)
  * Handle all OS-owned events on an 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)
+static int xhci_handle_events(struct xhci_hcd *xhci, struct xhci_interrupter *ir,
+			      bool skip_events)
 {
 	int event_loop = 0;
-	int err;
+	int err = 0;
 	u64 temp;
 
 	xhci_clear_interrupt_pending(ir);
@@ -3121,7 +3122,8 @@ static int xhci_handle_events(struct xhci_hcd *xhci, struct xhci_interrupter *ir
 
 	/* Process all OS owned event TRBs on this event ring */
 	while (unhandled_event_trb(ir->event_ring)) {
-		err = xhci_handle_event_trb(xhci, ir, ir->event_ring->dequeue);
+		if (!skip_events)
+			err = xhci_handle_event_trb(xhci, ir, ir->event_ring->dequeue);
 
 		/*
 		 * If half a segment of events have been handled in one go then
@@ -3148,6 +3150,37 @@ static int xhci_handle_events(struct xhci_hcd *xhci, struct xhci_interrupter *ir
 	return 0;
 }
 
+/*
+ * Move the event ring dequeue pointer to skip events kept in the secondary
+ * event ring.  This is used to ensure that pending events in the ring are
+ * acknowledged, so the xHCI HCD can properly enter suspend/resume.  The
+ * secondary ring is typically maintained by an external component.
+ */
+void xhci_skip_sec_intr_events(struct xhci_hcd *xhci,
+			       struct xhci_ring *ring,	struct xhci_interrupter *ir)
+{
+	union xhci_trb *current_trb;
+	u64 erdp_reg;
+	dma_addr_t deq;
+
+	/* disable irq, ack pending interrupt and ack all pending events */
+	xhci_disable_interrupter(ir);
+
+	/* last acked event trb is in erdp reg  */
+	erdp_reg = xhci_read_64(xhci, &ir->ir_set->erst_dequeue);
+	deq = (dma_addr_t)(erdp_reg & ERST_PTR_MASK);
+	if (!deq) {
+		xhci_err(xhci, "event ring handling not required\n");
+		return;
+	}
+
+	current_trb = ir->event_ring->dequeue;
+	/* read cycle state of the last acked trb to find out CCS */
+	ring->cycle_state = le32_to_cpu(current_trb->event_cmd.flags) & TRB_CYCLE;
+
+	xhci_handle_events(xhci, ir, true);
+}
+
 /*
  * xHCI spec says we can get an interrupt, and if the HC has an error condition,
  * we might get bad data out of the event ring.  Section 4.10.2.7 has a list of
@@ -3192,7 +3225,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
 	writel(status, &xhci->op_regs->status);
 
 	/* This is the handler of the primary interrupter */
-	xhci_handle_events(xhci, xhci->interrupters[0]);
+	xhci_handle_events(xhci, xhci->interrupters[0], false);
 out:
 	spin_unlock(&xhci->lock);
 

drivers/usb/host/xhci.h

@@ -1855,6 +1855,9 @@ xhci_create_secondary_interrupter(struct usb_hcd *hcd, unsigned int segs,
 				  u32 imod_interval);
 void xhci_remove_secondary_interrupter(struct usb_hcd
 				       *hcd, struct xhci_interrupter *ir);
+void xhci_skip_sec_intr_events(struct xhci_hcd *xhci,
+			       struct xhci_ring *ring,
+			       struct xhci_interrupter *ir);
 
 /* xHCI host controller glue */
 typedef void (*xhci_get_quirks_t)(struct device *, struct xhci_hcd *);
@@ -1940,6 +1943,9 @@ unsigned int count_trbs(u64 addr, u64 len);
 int xhci_stop_endpoint_sync(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
 			    int suspend, gfp_t gfp_flags);
 void xhci_process_cancelled_tds(struct xhci_virt_ep *ep);
+void xhci_update_erst_dequeue(struct xhci_hcd *xhci,
+			      struct xhci_interrupter *ir,
+			      bool clear_ehb);
 
 /* xHCI roothub code */
 void xhci_set_link_state(struct xhci_hcd *xhci, struct xhci_port *port,