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: .... -- Péter -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
