With 8250-dma, 8250-omap and am335x I observe the following: - start a RX transfer which will finish once the FIFO has enough data - The TX side starts a large TX transfer, say 1244 bytes. It takes approx 102ms for the transfer to complete - cancel the RX transfer & start the RX transfer a few times - the TX transfer completes. dma_irq_handler() notices this and schedules the completion callback - dma_ccerr_handler() is invoked. It returns IRQ_NONE because all four checked registers return 0. - the last irq handler is repeated a few times until the irq core shuts it down. I see the above describes pattern also without dma_ccerr_handler() beeing invoked. But if it is invoked, it always _after_ the dma interrupt handler for the TX handler was handled. If I disable TX-DMA for the UART then I don't see this dma_ccerr_handler() at all. Testing longer I see two addition scenarios of dma_ccerr_handler(): - EDMA_EMR0 reports 0x04000000 (the channel used by TX-UART). edma_callback() reports "looks like slot is null". Looks harmless. - EDMA_EMR0 reports the same values but later in the loop where a match search again EDMA_EMR0 reports 0 and so thing is done. Since it looks like the EDMA_EMR0 is loosing its content before the dma_ccerr_handler() is invoked, I suggest to unconditionally ack the interrupt so the irq core does not shut it down. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> --- arch/arm/common/edma.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/arm/common/edma.c b/arch/arm/common/edma.c index 88099175fc56..b31f3b7b3851 100644 --- a/arch/arm/common/edma.c +++ b/arch/arm/common/edma.c @@ -432,8 +432,10 @@ static irqreturn_t dma_ccerr_handler(int irq, void *data) if ((edma_read_array(ctlr, EDMA_EMR, 0) == 0) && (edma_read_array(ctlr, EDMA_EMR, 1) == 0) && (edma_read(ctlr, EDMA_QEMR) == 0) && - (edma_read(ctlr, EDMA_CCERR) == 0)) + (edma_read(ctlr, EDMA_CCERR) == 0)) { + edma_write(ctlr, EDMA_EEVAL, 1); return IRQ_NONE; + } while (1) { int j = -1; -- 2.1.0 -- 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