The synchronize_rcu() call resulting from making every serial driver
wake-up capable (commit b3b708fa) slows boot down by 600ms on my Tegra2x
system (with CONFIG_PREEMPT disabled).
Waking up the machine from a serial port seems to be an unlikely
requirement, so make serial_core default to not using the behaviour.
Before:
[ 0.338809] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
[ 0.951861] serial8250.0: ttyS0 at MMIO 0x70006040 (irq = 69) is a Tegra
[ 1.666042] console [ttyS0] enabled
After:
[ 0.338452] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
[ 0.339016] serial8250.0: ttyS0 at MMIO 0x70006040 (irq = 69) is a Tegra
[ 1.041860] console [ttyS0] enabled
Signed-off-by: Simon Glass <sjg@xxxxxxxxxxxx>
---
drivers/tty/serial/serial_core.c | 6 ++++--
include/linux/serial_core.h | 3 ++-
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index c7bf31a..0129551 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2348,8 +2348,10 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
*/
tty_dev = tty_register_device(drv->tty_driver, uport->line, uport->dev);
if (likely(!IS_ERR(tty_dev))) {
- device_init_wakeup(tty_dev, 1);
- device_set_wakeup_enable(tty_dev, 0);
+ if (uport->wakeup_capable) {
+ device_init_wakeup(tty_dev, 1);
+ device_set_wakeup_enable(tty_dev, 0);
+ }
} else
printk(KERN_ERR "Cannot register tty device on line %d\n",
uport->line);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index c91ace7..9a87975 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -377,7 +377,8 @@ struct uart_port {
unsigned char hub6; /* this should be in the 8250 driver */
unsigned char suspended;
unsigned char irq_wake;
- unsigned char unused[2];
+ unsigned char wakeup_capable; /* 1 if wake-up capable */
+ unsigned char unused;
void *private_data; /* generic platform data pointer */
};
--
1.7.7.3
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
