2013/12/18 Marek Vasut <ma...@denx.de>: > On Wednesday, December 18, 2013 at 08:24:49 AM, Kuo-Jung Su wrote: >> From: Kuo-Jung Su <dant...@faraday-tech.com> >> >> Because the EP0 fifo empty indication is non-reliable, >> an extra delay is necessary to avoid data corruption while >> handling packets with size greater than 64 bytes. >> >> This workaround should be applied to all hardware revisions. >> >> Signed-off-by: Kuo-Jung Su <dant...@faraday-tech.com> >> CC: Marek Vasut <ma...@denx.de> >> --- >> 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 e3a61cc..14bfec6 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_masked(1); > > Why don't you use regular udelay() here please ? Also, how exactly does the > delay help solving the unreliability problem please? >
1. No specific reason at all, I'll use regular udelay() in next version. :) 2. The fifo size of ep0 is 64 bytes, and my driver is supposed to make sure the fifo empty before filling up the fifo. 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.) And after a couple of tests, it looks like that 1 usec is good enough for this. >> writel(DMAFIFO_CX, ®s->dma_fifo); >> } else { >> /* Wait until epx fifo empty */ > > Best regards, > Marek Vasut -- Best wishes, Kuo-Jung Su _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot