* Peter Hurley | 2014-07-17 11:31:59 [-0400]: >On 07/16/2014 12:06 PM, Felipe Balbi wrote: >>On Wed, Jul 16, 2014 at 05:54:56PM +0200, Sebastian Andrzej Siewior wrote: >>>On 07/16/2014 05:16 PM, Felipe Balbi wrote: > >>>>I wonder if you should get_sync() on start_tx() and only >>>>put_autosuspend() at stop_tx(). I guess the outcome would be >>>>largely the same, no ? >>> >>>I just opened minicom on ttyS0 and gave a try. start_tx() was invoked >>>each time I pressed a key (sent a character). I haven't seen stop_tx() >>>even after after I closed minicom. I guess stop_tx() is invoked if you >>>switch half-duplex communication. >> >>that's bad, I expected stop to be called also after each character. > >The 8250 core auto-stops tx when the tx ring buffer is empty (except >in the case of dma, where stopping tx isn't necessary). This is correct. So this is what I have now for the non-dma case: diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 2e4a93b..480a1c0 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1283,6 +1283,9 @@ static inline void __stop_tx(struct uart_8250_port *p) if (p->ier & UART_IER_THRI) { p->ier &= ~UART_IER_THRI; serial_out(p, UART_IER, p->ier); + + pm_runtime_mark_last_busy(p->port.dev); + pm_runtime_put_autosuspend(p->port.dev); } } @@ -1310,12 +1313,12 @@ static void serial8250_start_tx(struct uart_port *port) struct uart_8250_port *up = container_of(port, struct uart_8250_port, port); - pm_runtime_get_sync(port->dev); if (up->dma && !serial8250_tx_dma(up)) { goto out; } else if (!(up->ier & UART_IER_THRI)) { up->ier |= UART_IER_THRI; + pm_runtime_get_sync(port->dev); serial_port_out(port, UART_IER, up->ier); if (up->bugs & UART_BUG_TXEN) { unsigned char lsr; @@ -1500,9 +1503,10 @@ void serial8250_tx_chars(struct uart_8250_port *up) uart_write_wakeup(port); DEBUG_INTR("THRE..."); - +#if 0 if (uart_circ_empty(xmit)) __stop_tx(up); +#endif } EXPORT_SYMBOL_GPL(serial8250_tx_chars); and now I need to come up with something that is not if (port != omap) for that #if 0 block. The code disables the TX FIFO empty interrupt once the transfer is complete. I want to call __stop_tx() once the tx fifo is empty. Felipe, Would a check for dev->power.use_autosuspend be the right thing to do? >Regards, >Peter Hurley Sebastian -- 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