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authorRussell King <rmk+lkml@arm.linux.org.uk>2008-02-04 22:27:52 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-05 09:44:10 -0800
commitc8c6bfa39d6bd7347f43937c8767ae145b61bcb4 (patch)
tree0d15a6faa56f7527359ea0360ca93e68010de02f /drivers/serial/serial_core.c
parent9d778a69370cc1b643b13648df971c83ff5654ef (diff)
downloadlinux-c8c6bfa39d6bd7347f43937c8767ae145b61bcb4.tar.bz2
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>
Diffstat (limited to 'drivers/serial/serial_core.c')
-rw-r--r--drivers/serial/serial_core.c8
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);
}