On Tue, 8 Jan 2008 11:57:03 +0000
Russell King <[EMAIL PROTECTED]> wrote:
> Some ports seem to be unable to drain their transmitters on shut down.
> Such a problem can occur if the port is programmed for hardware imposed
> flow control, characters are in the FIFO but the CTS signal is inactive.
>
> Normally, this isn't a problem because most places where we wait for the
> transmitter to drain have a time-out. However, there is no timeout in
> the suspend path.
>
> Give a port 30ms to drain; this is an arbitary value chosen to avoid
> long delays if there are many such ports in the system, while giving a
> reasonable chance for a single port to drain. Should a port not drain
> within this timeout, issue a warning.
>
> Signed-off-by: Russell King <[EMAIL PROTECTED]>
>
> diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
> index 3bb5d24..4ce219c 100644
> --- a/drivers/serial/serial_core.c
> +++ b/drivers/serial/serial_core.c
> @@ -1977,6 +1977,7 @@ int uart_suspend_port(struct uart_driver *drv, struct
> uart_port *port)
>
> if (state->info && state->info->flags & UIF_INITIALIZED) {
> const struct uart_ops *ops = port->ops;
> + int tries;
>
> state->info->flags = (state->info->flags & ~UIF_INITIALIZED)
> | UIF_SUSPENDED;
> @@ -1990,9 +1991,14 @@ int uart_suspend_port(struct uart_driver *drv, struct
> uart_port *port)
> /*
> * Wait for the transmitter to empty.
> */
> - while (!ops->tx_empty(port)) {
> + for (tries = 3; !ops->tx_empty(port) && tries; tries--) {
> msleep(10);
> }
> + if (!tries)
> + printk(KERN_ERR "%s%s%s%d: Unable to drain
> transmitter\n",
> + port->dev ? port->dev->bus_id : "",
> + port->dev ? ": " : "",
> + drv->dev_name, port->line);
>
> ops->shutdown(port);
> }
>
One hopes that doing a printk from within uart_suspend_port() will dtrt if
that port is (was?) being used as a console.
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