diff options
| author | Lu Baolu <baolu.lu@linux.intel.com> | 2017-03-21 16:01:29 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-03-21 12:28:45 +0100 |
| commit | dd759d93f4dd4fd2f345a78ad1223bb3edf3ee7b (patch) | |
| tree | 958cf26fd6ad3b034f345ebdb441c590a141aea0 /arch/x86/kernel/setup.c | |
| parent | 97da3854c526d3a6ee05c849c96e48d21527606c (diff) | |
| download | lwn-dd759d93f4dd4fd2f345a78ad1223bb3edf3ee7b.tar.gz lwn-dd759d93f4dd4fd2f345a78ad1223bb3edf3ee7b.zip | |
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@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-usb@vger.kernel.org
Link: http://lkml.kernel.org/r/1490083293-3792-2-git-send-email-baolu.lu@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/setup.c')
| -rw-r--r-- | arch/x86/kernel/setup.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 4bf0c8926a1c..e70204e13e48 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 |