[PATCH 2/3] usb: chipidea: udc: improve dTD link logic

[Xu Yang <xu.yang_2@nxp.com>]

Currently, ATDTW semaphore is used to safety link new dTD to dQH. But this
code has a bug when the endpoint is already in error before polling ATDTW
or just met error during polling ATDTW. In that cases, ATDTW will never
turn to 1 and the cpu will busy loop there.

When the endpoint met error, ENDPTSTAT will be cleared by HW. Therefore,
ENDPTSTAT should also be considered during this process. In case of
endpoint error, the current dTD should not be pushed to the head of dQH
since some dTDs may be still not executed. Therefore, the link logic is
also improved accordingly.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
---
 drivers/usb/chipidea/udc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
index b9ccf62e0a50..0ab57b87b07b 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -612,10 +612,17 @@ static int _hardware_enqueue(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq)
 		do {
 			hw_write(ci, OP_USBCMD, USBCMD_ATDTW, USBCMD_ATDTW);
 			tmp_stat = hw_read(ci, OP_ENDPTSTAT, BIT(n));
-		} while (!hw_read(ci, OP_USBCMD, USBCMD_ATDTW));
+		} while (!hw_read(ci, OP_USBCMD, USBCMD_ATDTW) && tmp_stat);
 		hw_write(ci, OP_USBCMD, USBCMD_ATDTW, 0);
 		if (tmp_stat)
 			goto done;
+
+		/* In case of error, ENDPTSTAT will also turn into 0, then
+		 * don't push this dTD to dQH head if current dTD pointer
+		 * is not the last dTD in previous request.
+		 */
+		if (hwep->qh.ptr->curr != prevlastnode->dma)
+			goto done;
 	}
 
 	/*  QH configuration */
-- 
2.34.1