From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751875AbdBNC1n (ORCPT ); Mon, 13 Feb 2017 21:27:43 -0500 Received: from mga04.intel.com ([192.55.52.120]:18309 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751734AbdBNC1l (ORCPT ); Mon, 13 Feb 2017 21:27:41 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,158,1484035200"; d="scan'208";a="64787092" From: Lu Baolu To: Greg Kroah-Hartman , Ingo Molnar Cc: Mathias Nyman , tglx@linutronix.de, peterz@infradead.org, linux-usb@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Lu Baolu Subject: [PATCH v7 1/5] x86: add simple udelay calibration Date: Tue, 14 Feb 2017 10:27:17 +0800 Message-Id: <1487039241-596-2-git-send-email-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1487039241-596-1-git-send-email-baolu.lu@linux.intel.com> References: <1487039241-596-1-git-send-email-baolu.lu@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a simple udelay calibration in x86 architecture-specific boot-time initializations. This will get a workable estimate for loops_per_jiffy. Hence, udelay() could be used after this initialization. Cc: Ingo Molnar Cc: x86@kernel.org Signed-off-by: Lu Baolu --- arch/x86/kernel/setup.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 4cfba94..aab7faa 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -835,6 +835,26 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p) return 0; } +static void __init simple_udelay_calibration(void) +{ + unsigned int tsc_khz, cpu_khz; + unsigned long lpj; + + if (!boot_cpu_has(X86_FEATURE_TSC)) + return; + + cpu_khz = x86_platform.calibrate_cpu(); + tsc_khz = x86_platform.calibrate_tsc(); + + tsc_khz = tsc_khz ? : cpu_khz; + if (!tsc_khz) + return; + + lpj = tsc_khz * 1000; + do_div(lpj, HZ); + loops_per_jiffy = lpj; +} + /* * Determine if we were loaded by an EFI loader. If so, then we have also been * passed the efi memmap, systab, etc., so we should use these data structures @@ -983,6 +1003,8 @@ void __init setup_arch(char **cmdline_p) */ x86_configure_nx(); + simple_udelay_calibration(); + parse_early_param(); #ifdef CONFIG_MEMORY_HOTPLUG -- 2.1.4