From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932774Ab2AST3K (ORCPT ); Thu, 19 Jan 2012 14:29:10 -0500 Received: from mail-gx0-f202.google.com ([209.85.161.202]:44901 "EHLO mail-gx0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932756Ab2AST3G (ORCPT ); Thu, 19 Jan 2012 14:29:06 -0500 From: Simon Glass To: LKML Cc: Greg Kroah-Hartman , linux-serial@vger.kernel.org, "Rafael J. Wysocki" , Alan Cox , "Paul E. McKenney" , Simon Glass Subject: [PATCH] serial: Fix wakeup init logic to speed up startup Date: Thu, 19 Jan 2012 11:28:56 -0800 Message-Id: <1327001336-28703-1-git-send-email-sjg@chromium.org> X-Mailer: git-send-email 1.7.7.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The synchronize_rcu() call resulting from making every serial driver wake-up capable (commit b3b708fa) slows boot down on my Tegra2x system (with CONFIG_PREEMPT disabled). But this is avoidable since it is the device_set_wakeup_enable() and then subsequence disable which causes the delay. We might as well just make the device wakeup capable but not actually enable it for wakeup until needed. Effectively the current code does this: device_set_wakeup_capable(dev, 1); device_set_wakeup_enable(dev, 1); device_set_wakeup_enable(dev, 0); We can just drop the last two lines. Before this change my boot log says: [ 0.227062] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled [ 0.702928] serial8250.0: ttyS0 at MMIO 0x70006040 (irq = 69) is a Tegra after: [ 0.227264] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled [ 0.227983] serial8250.0: ttyS0 at MMIO 0x70006040 (irq = 69) is a Tegra for saving of 450ms. Suggested-by: Rafael J. Wysocki Signed-off-by: Simon Glass --- drivers/tty/serial/serial_core.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index c7bf31a..1305618 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -2348,11 +2348,11 @@ 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); - } else + device_set_wakeup_capable(tty_dev, 1); + } else { printk(KERN_ERR "Cannot register tty device on line %d\n", uport->line); + } /* * Ensure UPF_DEAD is not set. -- 1.7.7.3