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| Started by | Lu Baolu <baolu.lu@linux.intel.com> |
|---|---|
| First post | 2017-02-14 03:30 +0100 |
| Last post | 2017-02-15 03:40 +0100 |
| Articles | 3 — 2 participants |
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[PATCH v7 1/5] x86: add simple udelay calibration Lu Baolu <baolu.lu@linux.intel.com> - 2017-02-14 03:30 +0100
Re: [PATCH v7 1/5] x86: add simple udelay calibration Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> - 2017-02-14 10:30 +0100
Re: [PATCH v7 1/5] x86: add simple udelay calibration Lu Baolu <baolu.lu@linux.intel.com> - 2017-02-15 03:40 +0100
| From | Lu Baolu <baolu.lu@linux.intel.com> |
|---|---|
| Date | 2017-02-14 03:30 +0100 |
| Subject | [PATCH v7 1/5] x86: add simple udelay calibration |
| Message-ID | <taB2p-3Rt-5@gated-at.bofh.it> |
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 4cfba94..aab7faa 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -835,6 +835,26 @@ 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
@@ -983,6 +1003,8 @@ 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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| From | Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> |
|---|---|
| Date | 2017-02-14 10:30 +0100 |
| Message-ID | <taHAR-8nm-11@gated-at.bofh.it> |
| In reply to | #1580225 |
Hello!
On 2/14/2017 5:27 AM, Lu Baolu wrote:
> 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 4cfba94..aab7faa 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -835,6 +835,26 @@ 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;
Why not:
if (!tsc_khz)
tsc_khz = cpu_khz;
It's more clear IMHO.
> + 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
[...]
MBR, Sergei
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| From | Lu Baolu <baolu.lu@linux.intel.com> |
|---|---|
| Date | 2017-02-15 03:40 +0100 |
| Message-ID | <taXFE-1Hw-19@gated-at.bofh.it> |
| In reply to | #1580424 |
Hi,
On 02/14/2017 05:23 PM, Sergei Shtylyov wrote:
> Hello!
>
> On 2/14/2017 5:27 AM, Lu Baolu wrote:
>
>> 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 4cfba94..aab7faa 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -835,6 +835,26 @@ 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;
>
> Why not:
>
> if (!tsc_khz)
> tsc_khz = cpu_khz;
>
> It's more clear IMHO.
Sure.
Best regards,
Lu Baolu
>
>> + 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
> [...]
>
> MBR, Sergei
>
>
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