On Thursday 13 October 2016 03:37 PM, Peter Ujfalusi wrote: > On 10/10/16 17:12, Peter Ujfalusi wrote: >> On 10/10/16 15:07, Vignesh R wrote: >>> From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> >>> >>> This DMA driver is used by 8250-omap on DRA7-evm. There is one >>> requirement that is to pause a transfer. This is currently used on the RX >>> side. It is possible that the UART HW aborted the RX (UART's RX-timeout) >>> but the DMA controller starts the transfer shortly after. >>> Before we can manually purge the FIFO we need to pause the transfer, >>> check how many bytes it already received and terminate the transfer >>> without it making any progress. >>> >>> From testing on the TX side it seems that it is possible that we invoke >>> pause once the transfer has completed which is indicated by the missing >>> CCR_ENABLE bit but before the interrupt has been noticed. In that case the >>> interrupt will come even after disabling it. >>> >>> The AM572x manual says that we have to wait for the CCR_RD_ACTIVE & >>> CCR_WR_ACTIVE bits to be gone before programming it again here is the >>> drain loop. Also it looks like without the drain the TX-transfer makes >>> sometimes progress. >>> >>> One note: The pause + resume combo is broken because after resume the >>> the complete transfer will be programmed again. That means the already >>> transferred bytes (until the pause event) will be sent again. This is >>> currently not important for my UART user because it does only pause + >>> terminate. >> >> Acked-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx> > > Can you resend the patch with corrected subject line? > dmaengine: omap-dma: .... > Sent v4 in reply to the patch fixing up the subject. Thanks! -- Regards Vignesh -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
