[PATCH] x86_64: remove check for CONSTANT_TSC from time.c

[PATCH] x86_64: remove check for CONSTANT_TSC from time.c

[Joerg Roedel]

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From: Joerg Roedel <joerg.roedel@amd.com>

This patch removes the check for the CONSTANT_TSC cpu flag from time.c
on the x86_64 architecture. At the time this flag is checked at boot the
cpu init code was yet not executed and thus the check fails. At this
point the check for VENDOR_AMD and cpu family 0x10 is sufficient.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

-- 
           |           AMD Saxony Limited Liability Company & Co. KG
 Operating |         Wilschdorfer Landstr. 101, 01109 Dresden, Germany
 System    |                  Register Court Dresden: HRA 4896
 Research  |              General Partner authorized to represent:
 Center    |             AMD Saxony LLC (Wilmington, Delaware, US)
           | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy

[-- Attachment #2: gh-tsc-fix-fix.patch --]
[-- Type: text/plain, Size: 548 bytes --]

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 4a0895b..8b29928 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -394,9 +394,9 @@ void __init time_init(void)
 	}
 
 	cpu_khz = tsc_khz;
-	if (cpu_has(&boot_cpu_data, X86_FEATURE_CONSTANT_TSC) &&
-		boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
+	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
 		boot_cpu_data.x86 == 16)
+		/* AMD Family 0x10 processors have a constant tsc */
 		cpu_khz = tsc_calibrate_cpu_khz();
 
 	if (unsynchronized_tsc())

Re: [PATCH] x86_64: remove check for CONSTANT_TSC from time.c

[Andi Kleen]

On Monday 04 June 2007 19:49, Joerg Roedel wrote:
> From: Joerg Roedel <joerg.roedel@amd.com>
>
> This patch removes the check for the CONSTANT_TSC cpu flag from time.c
> on the x86_64 architecture. At the time this flag is checked at boot the
> cpu init code was yet not executed and thus the check fails. At this
> point the check for VENDOR_AMD and cpu family 0x10 is sufficient.

Wrong fix. The bit just needs to be set earlier in early cpu detect. Otherwise 
there is a problem again with the next constant TSC AMD CPU.
I will do that.

-Andi

Re: [PATCH] x86_64: remove check for CONSTANT_TSC from time.c

[Joerg Roedel]

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On Mon, Jun 04, 2007 at 08:02:40PM +0200, Andi Kleen wrote:
> On Monday 04 June 2007 19:49, Joerg Roedel wrote:
> > From: Joerg Roedel <joerg.roedel@amd.com>
> >
> > This patch removes the check for the CONSTANT_TSC cpu flag from time.c
> > on the x86_64 architecture. At the time this flag is checked at boot the
> > cpu init code was yet not executed and thus the check fails. At this
> > point the check for VENDOR_AMD and cpu family 0x10 is sufficient.
> 
> Wrong fix. The bit just needs to be set earlier in early cpu detect. Otherwise 
> there is a problem again with the next constant TSC AMD CPU.
> I will do that.
> 
> -Andi

Ok. But I assume you are meaning something like the attached diff?

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

-- 
           |           AMD Saxony Limited Liability Company & Co. KG
 Operating |         Wilschdorfer Landstr. 101, 01109 Dresden, Germany
 System    |                  Register Court Dresden: HRA 4896
 Research  |              General Partner authorized to represent:
 Center    |             AMD Saxony LLC (Wilmington, Delaware, US)
           | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy

[-- Attachment #2: gh-tsc-fix-fix.patch --]
[-- Type: text/plain, Size: 921 bytes --]

diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index eb6524f..d16f7c2 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -806,6 +806,7 @@ void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
 			c->x86_model += ((tfms >> 16) & 0xF) << 4;
 		if (c->x86_capability[0] & (1<<19)) 
 			c->x86_clflush_size = ((misc >> 8) & 0xff) * 8;
+		c->extended_cpuid_level = cpuid_eax(0x80000000);
 	} else {
 		/* Have CPUID level 0 only - unheard of */
 		c->x86 = 4;
@@ -814,6 +815,12 @@ void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
 #ifdef CONFIG_SMP
 	c->phys_proc_id = (cpuid_ebx(1) >> 24) & 0xff;
 #endif
+
+	/* power flags are 8000_0007 edx. Bit 8 is constant TSC */
+	if ((c->x86_vendor == X86_VENDOR_AMD) &&
+	    (c->extended_cpuid_level >= 0x80000007) &&
+	    (cpuid_edx(0x80000007) & (1<<8)))
+		set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability);
 }
 
 /*

RE: [PATCH] x86_64: remove check for CONSTANT_TSC from time.c

[Nagendra, Bhavana]

Yes, the attached patch works for me.  Andi, is this patch acceptable?  

Regards,
--
Bhavana Nagendra
AMD, Inc
 
 

-----Original Message-----
From: Joerg Roedel [mailto:joerg.roedel@amd.com] 
Sent: Monday, June 04, 2007 4:42 PM
To: Andi Kleen
Cc: linux-kernel@vger.kernel.org; Deguara, Joachim; Nagendra, Bhavana
Subject: Re: [PATCH] x86_64: remove check for CONSTANT_TSC from time.c

On Mon, Jun 04, 2007 at 08:02:40PM +0200, Andi Kleen wrote:
> On Monday 04 June 2007 19:49, Joerg Roedel wrote:
> > From: Joerg Roedel <joerg.roedel@amd.com>
> >
> > This patch removes the check for the CONSTANT_TSC cpu flag from
time.c
> > on the x86_64 architecture. At the time this flag is checked at boot
the
> > cpu init code was yet not executed and thus the check fails. At this
> > point the check for VENDOR_AMD and cpu family 0x10 is sufficient.
> 
> Wrong fix. The bit just needs to be set earlier in early cpu detect.
Otherwise 
> there is a problem again with the next constant TSC AMD CPU.
> I will do that.
> 
> -Andi

Ok. But I assume you are meaning something like the attached diff?

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

-- 
           |           AMD Saxony Limited Liability Company & Co. KG
 Operating |         Wilschdorfer Landstr. 101, 01109 Dresden, Germany
 System    |                  Register Court Dresden: HRA 4896
 Research  |              General Partner authorized to represent:
 Center    |             AMD Saxony LLC (Wilmington, Delaware, US)
           | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe,
Thomas McCoy