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);
}
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
