[PATCH v2 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.

Fixes: 26c696c678c4 ("USB: Chipidea: rename struct ci13xxx variables from udc to ci")
Cc: stable@vger.kernel.org
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

---
Changes in v2:
 - modify comments
 - fix kernel test robot build warning by using cpu_to_le32
 - add fix tag and cc stable
---
 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 e0092c735a75..c0b8745234c6 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -752,10 +752,17 @@ 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;
+
+		/* OP_ENDPTSTAT will be clear by HW when the endpoint met
+		 * err. This dTD don't push to dQH if current dTD point is
+		 * not the last one in previous request.
+		 */
+		if (hwep->qh.ptr->curr != cpu_to_le32(prevlastnode->dma))
+			goto done;
 	}
 
 	/*  QH configuration */
-- 
2.34.1