On 02/23/2016 10:59 AM, Sekhar Nori wrote: >> With the am335x (Beaglebone Black, eDMA engine) I see 1000 DMA >> interrupts and 1000 spurious UART interrupts. The spurious UART >> interrupts arrive 30-50us _before_ the DMA interrupts. Always. >> >> If I disable UART timeout interrupts (RDI), the same test generates no >> spurious UART interrupts. Only 1000 DMA interrupts. > > To be clear, these interrupts are not caught as spurious by the > interrupt controller (INTC). They are detected by INTC as UART > interrupts. Just that you don't expect a timeout interrupt to happen at > the time you see the interrupt, correct? >From what I remember the INTC says it is UART, correct. But UART's status register says "no interrupt" (IIR has UART_IIR_NO_INT set). So the UART driver returns IRQ_NONE which counts as spurious. It is just that once you disable RDI there are no more interrupts coming during DMA transfer. > Thanks, > Sekhar > Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
