From: Kuo-Jung Su dantesu@faraday-tech.com
The fifo size of ep0 is 64 bytes, and if the packet size grater than 64 bytes, the driver would have to fill up the fifo multiple times, and before filling up the fifo, the driver should make sure the fifo is empty by checking fifo empty indication.
However there is a hardware bug that the fifo empty indication is somehow a bit earlier than fifo reset. So if I don't add an extra delay here, the data might be corrupted. (i.e., 1 byte missing)
After a couple of tests, it truns out that 1 usec is good enough.
This workaround should be applied to all hardware revisions.
Signed-off-by: Kuo-Jung Su dantesu@faraday-tech.com CC: Marek Vasut marex@denx.de --- Changes for v2: - udelay_masked() -> udelay(), and patch comment updates.
drivers/usb/gadget/fotg210.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/usb/gadget/fotg210.c b/drivers/usb/gadget/fotg210.c index cc5c507..3acf6a1 100644 --- a/drivers/usb/gadget/fotg210.c +++ b/drivers/usb/gadget/fotg210.c @@ -245,6 +245,7 @@ static int fotg210_dma(struct fotg210_ep *ep, struct fotg210_request *req) if (ep->id == 0) { /* Wait until cx/ep0 fifo empty */ fotg210_cxwait(chip, CXFIFO_CXFIFOE); + udelay(1); writel(DMAFIFO_CX, ®s->dma_fifo); } else { /* Wait until epx fifo empty */ -- 1.7.9.5