[PATCH] USB: gadget: atmel: fix transfer of queued requests

[Artur Rojek]

In the existing implementation, multiple requests queued up on an
endpoint are subject to getting evicted without transmission.

For both control and bulk endpoints, their respective logic found in
usba_control_irq()/usba_ep_irq() guarantees that TX FIFO is empty before
data is sent out, and that request_complete() gets called once the
transaction has been finished. At this point however, if any additional
requests are found on the endpoint queue, they will be processed by
submit_next_request(), which makes no checks against the above
conditions, trashing data on a busy FIFO and neglecting completion
handlers.

Fix the above issues by removing the calls to submit_next_request(),
and thus forcing the pending requests to be processed on the next pass
of the respective endpoint logic. While at it, remove a DBG message, as
that branch becomes part of regular flow.

This restores mass storage mode operation on Microchip ATSAMA5D27 SoC.

Signed-off-by: Artur Rojek <artur at conclusive.pl>
---
 drivers/usb/gadget/atmel_usba_udc.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/gadget/atmel_usba_udc.c b/drivers/usb/gadget/atmel_usba_udc.c
index 7d51821497b4..e6b458d940d8 100644
--- a/drivers/usb/gadget/atmel_usba_udc.c
+++ b/drivers/usb/gadget/atmel_usba_udc.c
@@ -57,13 +57,9 @@ static void submit_request(struct usba_ep *ep, struct usba_request *req)
 	req->submitted = 1;
 
 	next_fifo_transaction(ep, req);
-	if (req->last_transaction) {
-		usba_ep_writel(ep, CTL_DIS, USBA_TX_PK_RDY);
-		usba_ep_writel(ep, CTL_ENB, USBA_TX_COMPLETE);
-	} else {
+	if (ep_is_control(ep))
 		usba_ep_writel(ep, CTL_DIS, USBA_TX_COMPLETE);
-		usba_ep_writel(ep, CTL_ENB, USBA_TX_PK_RDY);
-	}
+	usba_ep_writel(ep, CTL_ENB, USBA_TX_PK_RDY);
 }
 
 static void submit_next_request(struct usba_ep *ep)
@@ -889,7 +885,6 @@ restart:
 			if (req) {
 				list_del_init(&req->queue);
 				request_complete(ep, req, 0);
-				submit_next_request(ep);
 			}
 			usba_ep_writel(ep, CTL_DIS, USBA_TX_COMPLETE);
 			ep->state = WAIT_FOR_SETUP;
@@ -1036,7 +1031,6 @@ static void usba_ep_irq(struct usba_udc *udc, struct usba_ep *ep)
 		DBG(DBG_BUS, "%s: TX PK ready\n", ep->ep.name);
 
 		if (list_empty(&ep->queue)) {
-			DBG(DBG_INT, "ep_irq: queue empty\n");
 			usba_ep_writel(ep, CTL_DIS, USBA_TX_PK_RDY);
 			return;
 		}
@@ -1050,7 +1044,6 @@ static void usba_ep_irq(struct usba_udc *udc, struct usba_ep *ep)
 
 		if (req->last_transaction) {
 			list_del_init(&req->queue);
-			submit_next_request(ep);
 			request_complete(ep, req, 0);
 		}
 
-- 
2.42.0