Commit-ID: dd759d93f4dd4fd2f345a78ad1223bb3edf3ee7b Gitweb: http://git.kernel.org/tip/dd759d93f4dd4fd2f345a78ad1223bb3edf3ee7b Author: Lu Baolu <baolu...@linux.intel.com> AuthorDate: Tue, 21 Mar 2017 16:01:29 +0800 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 21 Mar 2017 12:28:45 +0100
x86/timers: Add simple udelay calibration 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. Signed-off-by: Lu Baolu <baolu...@linux.intel.com> Acked-by: Thomas Gleixner <t...@linutronix.de> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: H. Peter Anvin <h...@zytor.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mathias Nyman <mathias.ny...@linux.intel.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: linux-...@vger.kernel.org Link: http://lkml.kernel.org/r/1490083293-3792-2-git-send-email-baolu...@linux.intel.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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 4bf0c89..e70204e 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -837,6 +837,26 @@ 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 @@ -985,6 +1005,8 @@ void __init setup_arch(char **cmdline_p) */ x86_configure_nx(); + simple_udelay_calibration(); + parse_early_param(); #ifdef CONFIG_MEMORY_HOTPLUG
