Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1605395

[PATCH v8 1/5] x86: add simple udelay calibration

Show all headers | View raw

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@redhat.com>
Cc: x86@kernel.org
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 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

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port Lu Baolu <baolu.lu@linux.intel.com> - 2017-03-21 09:10 +0100
  [PATCH v8 4/5] usb: serial: add dbc debug device support to usb_debug Lu Baolu <baolu.lu@linux.intel.com> - 2017-03-21 09:10 +0100
    [tip:x86/debug] usb/serial: Add DBC debug device support to  usb_debug tip-bot for Lu Baolu <tipbot@zytor.com> - 2017-03-21 13:30 +0100
  [PATCH v8 3/5] x86: add support for earlyprintk via USB3 debug port Lu Baolu <baolu.lu@linux.intel.com> - 2017-03-21 09:10 +0100
    [tip:x86/debug] x86/earlyprintk: Add support for earlyprintk via  USB3 debug port tip-bot for Lu Baolu <tipbot@zytor.com> - 2017-03-21 13:30 +0100
  [PATCH v8 1/5] x86: add simple udelay calibration Lu Baolu <baolu.lu@linux.intel.com> - 2017-03-21 09:10 +0100
    [tip:x86/debug] x86/timers: Add simple udelay calibration tip-bot for Lu Baolu <tipbot@zytor.com> - 2017-03-21 13:30 +0100
  [PATCH v8 5/5] usb: doc: add document for USB3 debug port usage Lu Baolu <baolu.lu@linux.intel.com> - 2017-03-21 09:10 +0100
    [tip:x86/debug] usb/doc: Add document for USB3 debug port usage tip-bot for Lu Baolu <tipbot@zytor.com> - 2017-03-21 13:30 +0100
  [PATCH v8 2/5] usb: early: add driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-03-21 09:10 +0100
    [tip:x86/debug] usb/early: Add driver for xhci debug capability tip-bot for Lu Baolu <tipbot@zytor.com> - 2017-03-21 13:30 +0100
  Re: [PATCH v8 0/5] usb: early: add support for early printk through  USB3 debug port Ingo Molnar <mingo@kernel.org> - 2017-03-21 12:40 +0100
    Re: [PATCH v8 0/5] usb: early: add support for early printk through  USB3 debug port Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-21 13:40 +0100
      Re: [PATCH v8 0/5] usb: early: add support for early printk through  USB3 debug port Ingo Molnar <mingo@kernel.org> - 2017-03-21 13:50 +0100
    Re: [PATCH v8 0/5] usb: early: add support for early printk through  USB3 debug port Lu Baolu <baolu.lu@linux.intel.com> - 2017-03-22 03:30 +0100

csiph-web