From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754538Ab2AaEtu (ORCPT ); Mon, 30 Jan 2012 23:49:50 -0500 Received: from casper.infradead.org ([85.118.1.10]:45737 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753913Ab2AaEtt convert rfc822-to-8bit (ORCPT ); Mon, 30 Jan 2012 23:49:49 -0500 Date: Mon, 30 Jan 2012 20:51:20 -0800 From: Arjan van de Ven To: linux-kernel@vger.kernel.org Cc: John Stultz , Thomas Gleixner , Len Brown , arjanvandeven@gmail.com Subject: [PATCH] clocksource: Load the ACPI PM clocksource asynchronously Message-ID: <20120130205120.652aa64f@infradead.org> Organization: Intel X-Mailer: Claws Mail 3.7.9 (GTK+ 2.24.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From ef4b0d23878277dfd75828f13353e605aae2937f Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Mon, 30 Jan 2012 20:23:30 -0800 Subject: [PATCH] clocksource: Load the ACPI PM clocksource asynchronously The ACPI clocksource takes quite some time to initialize, and this increases the boot time of the kernel for a double digit percentage. This while almost all modern systems will be using the HPET already anyway. This patch turns the clocksource loading into an asynchronous operation; which means it won't hold up the boot while still becoming available normally. To make this work well, an udelay() had to be turned into an usleep_range() so that on UP systems, we yield the CPU to regular boot tasks instead of spinning. CC: John Stultz CC: Thomas Gleixner CC: Len Brown Signed-off-by: Arjan van de Ven --- drivers/clocksource/acpi_pm.c | 24 ++++++++++++++++-------- 1 files changed, 16 insertions(+), 8 deletions(-) diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c index 6b5cf02..82e8820 100644 --- a/drivers/clocksource/acpi_pm.c +++ b/drivers/clocksource/acpi_pm.c @@ -23,6 +23,7 @@ #include #include #include +#include #include /* @@ -179,17 +180,15 @@ static int verify_pmtmr_rate(void) /* Number of reads we try to get two different values */ #define ACPI_PM_READ_CHECKS 10000 -static int __init init_acpi_pm_clocksource(void) +static void __init acpi_pm_clocksource_async(void *unused, async_cookie_t cookie) { cycle_t value1, value2; unsigned int i, j = 0; - if (!pmtmr_ioport) - return -ENODEV; /* "verify" this timing source: */ for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) { - udelay(100 * j); + usleep_range(100 * j, 100 * j + 100); value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm); for (i = 0; i < ACPI_PM_READ_CHECKS; i++) { value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm); @@ -203,25 +202,34 @@ static int __init init_acpi_pm_clocksource(void) " 0x%#llx, 0x%#llx - aborting.\n", value1, value2); pmtmr_ioport = 0; - return -EINVAL; + return; } if (i == ACPI_PM_READ_CHECKS) { printk(KERN_INFO "PM-Timer failed consistency check " " (0x%#llx) - aborting.\n", value1); pmtmr_ioport = 0; - return -ENODEV; + return; } } if (verify_pmtmr_rate() != 0){ pmtmr_ioport = 0; - return -ENODEV; + return; } - return clocksource_register_hz(&clocksource_acpi_pm, + clocksource_register_hz(&clocksource_acpi_pm, PMTMR_TICKS_PER_SEC); } +static int __init init_acpi_pm_clocksource(void) +{ + if (!pmtmr_ioport) + return -ENODEV; + + async_schedule(acpi_pm_clocksource_async, NULL); + return 0; +} + /* We use fs_initcall because we want the PCI fixups to have run * but we still need to load before device_initcall */ -- 1.7.6.4 -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org