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Date: Tue, 24 Feb 2009 08:08:58 +0100
From: Frans Pop <elendil@...net.nl>
To: Dave Jones <davej@...hat.com>
Cc: Mattias-Christian Ott <ott@...ix.org>,
Dominik Brodowski <linux@...do.de>,
Joerg Platte <jplatte@...sa.net>,
Matthew Garrett <mjg59@...f.ucam.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
cpufreq@...r.kernel.org
Subject: [PATCH] p4-clockmod: Calculate frequency based on TSC value for P4 models 0 and 1
From: Mattias-Christian Ott <ott@...ix.org>
Commit ed9cbcd40004904dbe61ccc16d6106a7de38c998 reverted an incorrect
change that resulted in random frequencies being displayed in some cases
for early P4 models because the MSR_FBC_REGISTER_ID ratio is undefined.
Result of the revert is that for some users the CPU frequency is displayed
multiplied by a factor 8 in /proc/cpuinfo when p4-clockmod is loaded.
Calculating the frequency from the TSC value should work in all cases.
Signed-off-by: Mattias-Christian Ott <ott@...ix.org>
Signed-off-by: Frans Pop <elendil@...net.nl>
Acked-by: Dominik Brodowski <linux@...do.de>
Tested-by: Joerg Platte <jplatte@...sa.net>
Cc: Dave Jones <davej@...hat.com>
Cc: Matthew Garrett <mjg59@...f.ucam.org>
---
This patch has been submitted before, but seems to have gotten lost:
http://bugzilla.kernel.org/show_bug.cgi?id=10968
I'm resubmitting it as it has been verified to solve a post-2.6.24
regression reported by Joerg Platte:
http://www.gossamer-threads.com/lists/linux/kernel/1034291?page=last
I've been unable to find the actual submission mail, so I've created
a new patch description and added the appropriate signed-off lines.
diff --git a/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c b/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
index b585e04..a4dcc65 100644
--- a/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
+++ b/arch/x86/kernel/cpu/cpufreq/p4-clockmod.c
@@ -30,6 +30,7 @@
#include <asm/processor.h>
#include <asm/msr.h>
+#include <asm/timer.h>
#include <asm/timex.h>
#include "speedstep-lib.h"
@@ -217,6 +218,11 @@ static int cpufreq_p4_cpu_init(struct cpufreq_policy *policy)
dprintk("has errata -- disabling low frequencies\n");
}
+ if (speedstep_detect_processor() == SPEEDSTEP_PROCESSOR_P4D && c->x86_model < 2) {
+ /* switch to maximum frequency and measure result */
+ cpufreq_p4_setdc(policy->cpu, DC_DISABLE);
+ recalibrate_cpu_khz();
+ }
/* get max frequency */
stock_freq = cpufreq_p4_get_frequency(c);
if (!stock_freq)
diff --git a/arch/x86/kernel/cpu/cpufreq/speedstep-lib.c b/arch/x86/kernel/cpu/cpufreq/speedstep-lib.c
index cdac7d6..919644c 100644
--- a/arch/x86/kernel/cpu/cpufreq/speedstep-lib.c
+++ b/arch/x86/kernel/cpu/cpufreq/speedstep-lib.c
@@ -16,6 +16,7 @@
#include <linux/slab.h>
#include <asm/msr.h>
+#include <asm/tsc.h>
#include "speedstep-lib.h"
#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "speedstep-lib", msg)
@@ -167,6 +168,15 @@ static unsigned int pentium4_get_frequency(void)
struct cpuinfo_x86 *c = &boot_cpu_data;
u32 msr_lo, msr_hi, mult;
unsigned int fsb = 0;
+ u8 fsb_code;
+
+ /* Pentium 4 Model 0 and 1 do not have the Core Clock Frequency
+ * to System Bus Frequency Ratio Field in the Processor Frequency
+ * Configuration Register of the MSR. Therefore the current
+ * frequency cannot be calculated and has to be measured.
+ */
+ if (c->x86_model < 2)
+ return cpu_khz;
rdmsr(0x2c, msr_lo, msr_hi);
@@ -177,21 +187,17 @@ static unsigned int pentium4_get_frequency(void)
* revision #12 in Table B-1: MSRs in the Pentium 4 and
* Intel Xeon Processors, on page B-4 and B-5.
*/
- if (c->x86_model < 2)
+ fsb_code = (msr_lo >> 16) & 0x7;
+ switch (fsb_code) {
+ case 0:
fsb = 100 * 1000;
- else {
- u8 fsb_code = (msr_lo >> 16) & 0x7;
- switch (fsb_code) {
- case 0:
- fsb = 100 * 1000;
- break;
- case 1:
- fsb = 13333 * 10;
- break;
- case 2:
- fsb = 200 * 1000;
- break;
- }
+ break;
+ case 1:
+ fsb = 13333 * 10;
+ break;
+ case 2:
+ fsb = 200 * 1000;
+ break;
}
if (!fsb)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 599e581..19ccb3b 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -524,7 +524,6 @@ unsigned long native_calibrate_tsc(void)
}
#ifdef CONFIG_X86_32
-/* Only called from the Powernow K7 cpu freq driver */
int recalibrate_cpu_khz(void)
{
#ifndef CONFIG_SMP
--
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