* Frans Klaver | 2014-09-08 16:46:18 [+0200]: >- ncurses based applications (vi, less) don't play nice for me on the > console with this series. less doesn't show me anything. vi doesn't > return to console properly. Can you give a test case >- I seem seem to get stuck in a "serial8250: too much work for irq%d" > loop somewhat reliably. We have a rather demanding application with > typically somewhere between 600 and 1000 byte packets being sent at > 240Hz (roughly somewhere between 1.5 and 2 Mb/s). We run at baudrate > 3500k. I get into this "too much work" thing already when running at > 300 bytes per packet. Do you get this message also at lower baud rates, say 115200? What I am trying to understand is why you are spinning in the handler. _With_ DMA you should hardly get into the serial handler under normal conditions. Running at 3.5MB/sec should give one byte every 2.8us and 48 Bytes every ~137us. This looks like plenty of time to get out of the handler. My *guess* is that serial8250_handle_irq() has IIR often set to timeout and you end up fetching byte after byte. This patch should protocol when and why you got into the handler. diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 7111b22de000..59852069e4a0 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1583,6 +1583,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir) status = serial_port_in(port, UART_LSR); DEBUG_INTR("status = %x...", status); + trace_printk("l%d IIR %x LSR %x\n", port->line, iir, status); if (status & (UART_LSR_DR | UART_LSR_BI)) { if (up->dma) @@ -1707,6 +1708,7 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id) spin_unlock(&i->lock); + trace_printk("%d e\n", irq); DEBUG_INTR("end.\n"); return IRQ_RETVAL(handled); >I hope this is of some use to you. I'll do more testing later. Which SoC do you use and do you have DMA enabled? >Thanks, >Frans 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