diff mbox series

[v2] usb: cdnsp: Fix issue with detecting command completion event

Message ID PH7PR07MB9538AA45362ACCF1B94EE9B7DD96A@PH7PR07MB9538.namprd07.prod.outlook.com
State New
Headers show
Series [v2] usb: cdnsp: Fix issue with detecting command completion event | expand

Commit Message

Pawel Laszczak May 13, 2025, 5:30 a.m. UTC 
In some cases, there is a small-time gap in which CMD_RING_BUSY
can be cleared by controller but adding command completion event
to event ring will be delayed. As the result driver will return
error code.
This behavior has been detected on usbtest driver (test 9) with
configuration including ep1in/ep1out bulk and ep2in/ep2out isoc
endpoint.
Probably this gap occurred because controller was busy with adding
some other events to event ring.
The CMD_RING_BUSY is cleared to '0' when the Command Descriptor
has been executed and not when command completion event has been
added to event ring.

To fix this issue for this test the small delay is sufficient
less than 10us) but to make sure the problem doesn't happen again
in the future the patch introduces 10 retries to check with delay
about 20us before returning error code.

Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
cc: stable@vger.kernel.org
Signed-off-by: Pawel Laszczak <pawell@cadence.com>
---
Changelog:
v2:
- replaced usleep_range with udelay
- increased retry counter and decreased the udelay value

 drivers/usb/cdns3/cdnsp-gadget.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/usb/cdns3/cdnsp-gadget.c b/drivers/usb/cdns3/cdnsp-gadget.c
index 4824a10df07e..58650b7f4173 100644
--- a/drivers/usb/cdns3/cdnsp-gadget.c
+++ b/drivers/usb/cdns3/cdnsp-gadget.c
@@ -547,6 +547,7 @@  int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
 	dma_addr_t cmd_deq_dma;
 	union cdnsp_trb *event;
 	u32 cycle_state;
+	u32 retry = 10;
 	int ret, val;
 	u64 cmd_dma;
 	u32  flags;
@@ -578,8 +579,23 @@  int cdnsp_wait_for_cmd_compl(struct cdnsp_device *pdev)
 		flags = le32_to_cpu(event->event_cmd.flags);
 
 		/* Check the owner of the TRB. */
-		if ((flags & TRB_CYCLE) != cycle_state)
+		if ((flags & TRB_CYCLE) != cycle_state) {
+			/*
+			 * Give some extra time to get chance controller
+			 * to finish command before returning error code.
+			 * Checking CMD_RING_BUSY is not sufficient because
+			 * this bit is cleared to '0' when the Command
+			 * Descriptor has been executed by controller
+			 * and not when command completion event has
+			 * be added to event ring.
+			 */
+			if (retry--) {
+				udelay(20);
+				continue;
+			}
+
 			return -EINVAL;
+		}
 
 		cmd_dma = le64_to_cpu(event->event_cmd.cmd_trb);