[RFC] [PATCH] usb: gadget: fix dtd dma confusion

[Christoph Fritz <chf.fritz@googlemail.com>]

On Wed, Apr 11, 2012 at 10:15:49AM -0300, Fabio Estevam wrote:
> On Wed, Apr 11, 2012 at 4:39 AM, Christoph Fritz
> <chf.fritz@googlemail.com> wrote:
> 
> > Can you approve this behaviour of g_ether/usbnet when using iperf?
> 
> I am not very familiar with iperf, so I will let others comment.

Hi to All,

after a while of testing and searching I can come up with a patch
that fixes g_ether <-> iperf for fsl_udc on ARM i.MX35.

The sad part is that this kind of fix is already implemented for
marvell mv_udc driver since last year but still _not_ in the ~15
other *udc.c drivers.

See here:
daec765da767e4a6a30e1298862b28f2cae9a73f
usb: gadget: mv_udc: fix dtd dma confusion

So hereby I'm CC-ing all *udc.c maintainers to point out that this
issue maybe affects you too.

And maybe someone can explain if this: 
+				if (curr_td->next_td_ptr == EP_QUEUE_HEAD_NEXT_TERMINATE) {
is necessary and why (please see below).


Thanks,
 -- Christoph

---
Subject: [PATCH] usb: gadget: fsl_udc: fix dtd dma confusion

The controller will hang when doing testings with g_ether and iperf
(tool for measuring maximum TCP and UDP bandwidth).  This patch adds a
delay to wait for controller to release dtd dma before freeing it.

Signed-off-by: Christoph Fritz <chf.fritz@googlemail.com>
---
 drivers/usb/gadget/fsl_udc_core.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/usb/gadget/fsl_udc_core.c b/drivers/usb/gadget/fsl_udc_core.c
index 55abfb6..fc86108 100644
--- a/drivers/usb/gadget/fsl_udc_core.c
+++ b/drivers/usb/gadget/fsl_udc_core.c
@@ -1638,6 +1638,15 @@ static int process_ep_req(struct fsl_udc *udc, int pipe,
 			status = REQ_UNCOMPLETE;
 			return status;
 		} else if (remaining_length) {
+			/* wait controller release dtd dma */
+			while ((curr_qh->curr_dtd_ptr == curr_td->td_dma)) {
+				if (curr_td->next_td_ptr ==
+						EP_QUEUE_HEAD_NEXT_TERMINATE) {
+					udelay(100);
+					break;
+				}
+				udelay(1);
+			}
 			if (direction) {
 				VDBG("Transmit dTD remaining length not zero");
 				status = -EPROTO;
-- 
1.7.2.5