On Saturday 17 June 2017 08:07 PM, Andy Shevchenko wrote:
> On Sat, 2017-06-17 at 19:22 +0530, Vignesh R wrote:
>> DMA RX completion handler for UART is called from a tasklet and hence
>> may be delayed depending on the system load. In meanwhile, there may
>> be
>> RX timeout interrupt which can get serviced first before DMA RX
>> completion handler is executed for the completed transfer.
>> omap_8250_rx_dma_flush() which is called on RX timeout interrupt makes
>> sure that the DMA RX buffer is pushed and then the FIFO is drained and
>> also queues a new DMA request. But, when DMA RX completion handler
>> executes, it will erroneously flush the currently queued DMA transfer
>> which sometimes results in data corruption and double queueing of DMA
>> RX
>> requests.
>>
>> Fix this by checking whether RX completion is for the currently queued
>> transfer or not. And also hold port lock when in DMA completion to
>> avoid
>> race wrt RX timeout handler preempting it.
>
>
>> static void __dma_rx_complete(void *param)
>> {
>> - __dma_rx_do_complete(param);
>> - omap_8250_rx_dma(param);
>> + struct uart_8250_port *p = param;
>> + struct uart_8250_dma *dma = p->dma;
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&p->port.lock, flags);
>> +
>> + /*
>> + * If the completion is for the current cookie then handle
>> it,
>> + * else a previous RX timeout flush would have already pushed
>> + * data from DMA buffers, so exit.
>> + */
>
>> + if (dma->rx_cookie != dma->rxchan->completed_cookie) {
>
> Wouldn't be better to call DMAEngine API for that?
> dmaengine_tx_status() I suppose
Yeah, will update the patch. Thanks!
--
Regards
Vignesh
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