Commit-ID: dd759d93f4dd4fd2f345a78ad1223bb3edf3ee7b
Gitweb: http://git.kernel.org/tip/dd759d93f4dd4fd2f345a78ad1223bb3edf3ee7b
Author: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
AuthorDate: Tue, 21 Mar 2017 16:01:29 +0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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.lu@xxxxxxxxxxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: linux-usb@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1490083293-3792-2-git-send-email-baolu.lu@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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
--
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