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 <mingo@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
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
--
2.1.4
--
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