From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932446AbbEHRs0 (ORCPT ); Fri, 8 May 2015 13:48:26 -0400 Received: from mail-vn0-f51.google.com ([209.85.216.51]:43520 "EHLO mail-vn0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753101AbbEHRsU (ORCPT ); Fri, 8 May 2015 13:48:20 -0400 From: Len Brown To: x86@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Len Brown Subject: [PATCH 1/2] x86: Add cmdline "cpu_init_udelay=N" to specify cpu_up() delay Date: Fri, 8 May 2015 13:48:06 -0400 Message-Id: <3f51dfd7de5bf660b62d01216edce41b0904fddf.1431106775.git.len.brown@intel.com> X-Mailer: git-send-email 2.4.0.rc1 In-Reply-To: <1431107287-22022-1-git-send-email-lenb@kernel.org> References: <1431107287-22022-1-git-send-email-lenb@kernel.org> Reply-To: Len Brown Organization: Intel Open Source Technology Center Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Len Brown No change to default behavior. Replace the hard-coded mdelay(10) in cpu_up() with a variable udelay, that is set to a defined default -- rather than a magic number. Add a boot-time override, "cpu_init_udelay=N" Signed-off-by: Len Brown --- Documentation/kernel-parameters.txt | 6 ++++++ arch/x86/kernel/smpboot.c | 23 ++++++++++++++++++++++- 2 files changed, 28 insertions(+), 1 deletion(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index bfcb1a6..0a16309 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -737,6 +737,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. cpuidle.off=1 [CPU_IDLE] disable the cpuidle sub-system + cpu_init_udelay=N + [X86] Delay for N microsec between assert and de-assert + of APIC INIT to start processors. This delay occurs + on every CPU online, such as boot, and resume from suspend. + Default: 10000 + cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver Format: ,,,[,] diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index febc6aa..0ddc28b 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -517,6 +517,27 @@ void __inquire_remote_apic(int apicid) } /* + * The Multiprocessor Specification 1.4 (1997) example code suggests + * that there should be a 10ms delay between the BSP asserting INIT + * and de-asserting INIT, when starting a remote processor. + * But that slows boot and resume on modern processors, which include + * many cores and don't require that delay. + * + * Cmdline "init_cpu_udelay=" is available to over-ride this delay. + */ +#define UDELAY_10MS_DEFAULT 10000 + +static unsigned int init_udelay = UDELAY_10MS_DEFAULT; + +static int __init cpu_init_udelay(char *str) +{ + get_option(&str, &init_udelay); + + return 0; +} +early_param("cpu_init_udelay", cpu_init_udelay); + +/* * Poke the other CPU in the eye via NMI to wake it up. Remember that the normal * INIT, INIT, STARTUP sequence will reset the chip hard for us, and this * won't ... remember to clear down the APIC, etc later. @@ -586,7 +607,7 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip) pr_debug("Waiting for send to finish...\n"); send_status = safe_apic_wait_icr_idle(); - mdelay(10); + udelay(init_udelay); pr_debug("Deasserting INIT\n"); -- 2.4.0.rc1