Hi, On Thu, Apr 17, 2014 at 1:38 AM, Paul Zimmerman <Paul.Zimmerman@xxxxxxxxxxxx> wrote: >> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of sundeep subbaraya >> Sent: Wednesday, April 16, 2014 3:39 AM >> >> Hi Felipe, >> >> On Thu, Apr 3, 2014 at 8:28 PM, Felipe Balbi <balbi@xxxxxx> wrote: >> >> >> +static int start_dma(struct xusb_ep *ep, u32 src, u32 dst, u32 length) >> > >> > please prepend this with xudc_, it makes tracing a lot easier. >> > >> >> +{ >> >> + struct xusb_udc *udc; >> >> + int rc = 0; >> >> + unsigned long timeout; >> >> + >> >> + udc = ep->udc; >> >> + /* >> >> + * Set the addresses in the DMA source and >> >> + * destination registers and then set the length >> >> + * into the DMA length register. >> >> + */ >> >> + udc->write_fn(udc->base_address, XUSB_DMA_DSAR_ADDR_OFFSET, src); >> >> + udc->write_fn(udc->base_address, XUSB_DMA_DDAR_ADDR_OFFSET, dst); >> >> + udc->write_fn(udc->base_address, XUSB_DMA_LENGTH_OFFSET, length); >> >> + >> >> + /* >> >> + * Wait till DMA transaction is complete and >> >> + * check whether the DMA transaction was >> >> + * successful. >> >> + */ >> >> + while ((udc->read_fn(ep->udc->base_address + XUSB_DMA_STATUS_OFFSET) & >> >> + XUSB_DMA_DMASR_BUSY) == XUSB_DMA_DMASR_BUSY) { >> >> + timeout = jiffies + 10000; >> >> + >> >> + if (time_after(jiffies, timeout)) { >> >> + rc = -ETIMEDOUT; >> >> + goto clean; >> >> + } >> >> + } >> > >> > don't you get an IRQ for DMA completion ? If you do, you could be using >> > wait_for_completion() >> >> This function is called in interrupt context when buffer is ready or >> free. It initiates >> DMA to transfer data from IP buffer to memory. Hence it waits in busy >> loop till DMA >> completes > > If this function is called in interrupt context, then you can't use > jiffies for your timeout, since jiffies may not get updated while in > interrupt context. Yes. It is obvious that this logic is buggy, will change this. Thanks, Sundeep.B.S. > > -- > Paul > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
