[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 <ar...@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