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| author | Russell King <rmk+lkml@arm.linux.org.uk> | 2008-02-04 22:27:52 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-05 09:44:10 -0800 |
| commit | c8c6bfa39d6bd7347f43937c8767ae145b61bcb4 (patch) | |
| tree | 0d15a6faa56f7527359ea0360ca93e68010de02f | |
| parent | 9d778a69370cc1b643b13648df971c83ff5654ef (diff) | |
| download | linux-c8c6bfa39d6bd7347f43937c8767ae145b61bcb4.tar.gz linux-c8c6bfa39d6bd7347f43937c8767ae145b61bcb4.tar.bz2 linux-c8c6bfa39d6bd7347f43937c8767ae145b61bcb4.zip | |
serial: avoid stalling suspend if serial port won't drain
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 <rmk+kernel@arm.linux.org.uk>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | drivers/serial/serial_core.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c index 2554d2fa6542..304fe32eb066 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); } |