[RFC] [PATCH]:Obtain FSB ratio from model string

[RFC] [PATCH]:Obtain FSB ratio from model string

[Zhao Yakui]

Hi, all
        According to the document of 253369(intel), the ratio is
undefined in MSR_FBC_REGSITER_ID. The following calculation is
inappropriate.
if (c->x86_model < 2)
        mult = msr_lo >> 27;

There are two ways to fix this problem.
a. use the following patch. the ratio is obtained from model string.
b. revert the commit until the proper patch is available.

http://git.kernel.org/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=3e4159ab35c88aef5e063ba78796b277b762a30a


Subject: ACPI :Obtain FSB ratio from model string when model is less than 2
>From : Zhao Yakui <yakui.zhao@intel.com>

The ratio is undefined in the register of MSR_FBC_REGSITER_ID 
when the model for P4 is less than 2. The following calculation is 
inappropriate.
if (c->x86_model < 2)
	mult = msr_lo >> 27;
In order to support the speedstep , the FSb ratio can be obtained from 
the model_id string. 
For example:
The ratio is 13 for model string:"Intel(R) Pentium(R) 4 CPU 1300MHz"

http://bugzilla.kernel.org/show_bug.cgi?id=7186

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
---
 arch/i386/kernel/cpu/cpufreq/speedstep-lib.c |   40 +++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

Index: linux-2.6.23-rc9/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
===================================================================
--- linux-2.6.23-rc9.orig/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
+++ linux-2.6.23-rc9/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
@@ -17,6 +17,7 @@
 
 #include <asm/msr.h>
 #include "speedstep-lib.h"
+#include <linux/ctype.h>
 
 #define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "speedstep-lib", msg)
 
@@ -151,7 +152,40 @@ static unsigned int pentium_core_get_fre
 
 	return (msr_tmp * fsb);
 }
-
+/* When Model_id is less than 2, the FSB ratio is
+obtained from the string of model_id */
+static unsigned int p4_01_get_fsb_ratio(void)
+{
+	struct cpuinfo_x86 *c = &boot_cpu_data;
+	unsigned int fsb_m;
+	char model_id[64];
+	unsigned int  freq_mhz;
+	unsigned int max_ratio;
+	char *ptr;
+	int i = 0;
+
+	ptr = model_id;
+	strncpy(ptr, c->x86_model_id, strlen(c->x86_model_id));
+	for (i = 0; i < strlen(model_id); i++)
+		model_id[i] = tolower(model_id[i]);
+	if (strstr(model_id, "mhz"))
+		fsb_m = 100;
+	else
+		fsb_m = 0;
+	if (!fsb_m) {
+		printk(KERN_DEBUG "CPU doesn't support speedstep\n");
+		return 0;
+	}
+	ptr = strstr(model_id, "hz");
+	if (ptr)
+		*ptr = '\0';
+	freq_mhz = 0;
+	ptr = strrchr(model_id, ' ');
+	if (ptr)
+		sscanf(ptr, "%d", &freq_mhz);
+	max_ratio = freq_mhz / fsb_m;
+	return max_ratio;
+}
 
 static unsigned int pentium4_get_frequency(void)
 {
@@ -189,8 +223,10 @@ static unsigned int pentium4_get_frequen
 		printk(KERN_DEBUG "speedstep-lib: couldn't detect FSB speed. Please send an e-mail to <linux@brodo.de>\n");
 
 	/* Multiplier. */
+	/* if Model is less than 2 , the ratio is obtained from the
+	 * string of model_id */
 	if (c->x86_model < 2)
-		mult = msr_lo >> 27;
+		mult = p4_01_get_fsb_ratio();
 	else
 		mult = msr_lo >> 24;
 

Re: [RFC] [PATCH]:Obtain FSB ratio from model string

[Len Brown]

On Friday 26 October 2007 01:43, Zhao Yakui wrote:
> Hi, all
>         According to the document of 253369(intel), the ratio is
> undefined in MSR_FBC_REGSITER_ID. The following calculation is
> inappropriate.
> if (c->x86_model < 2)
>         mult = msr_lo >> 27;
> 
> There are two ways to fix this problem.
> a. use the following patch. the ratio is obtained from model string.
> b. revert the commit until the proper patch is available.
> 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=3e4159ab35c88aef5e063ba78796b277b762a30a

Okay, I've reverted that patch -- so model 0&1 are back to where they were in 2005
and random MHz is replaced by other random MHz.

> 
> Subject: ACPI :Obtain FSB ratio from model string when model is less than 2
> >From : Zhao Yakui <yakui.zhao@intel.com>
> 
> The ratio is undefined in the register of MSR_FBC_REGSITER_ID 
> when the model for P4 is less than 2. The following calculation is 
> inappropriate.
> if (c->x86_model < 2)
> 	mult = msr_lo >> 27;
> In order to support the speedstep , the FSb ratio can be obtained from 
> the model_id string. 
> For example:
> The ratio is 13 for model string:"Intel(R) Pentium(R) 4 CPU 1300MHz"
> 
> http://bugzilla.kernel.org/show_bug.cgi?id=7186
> 
> Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
> ---
>  arch/i386/kernel/cpu/cpufreq/speedstep-lib.c |   40 +++++++++++++++++++++++++--
>  1 file changed, 38 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6.23-rc9/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
> ===================================================================
> --- linux-2.6.23-rc9.orig/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
> +++ linux-2.6.23-rc9/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
> @@ -17,6 +17,7 @@
>  
>  #include <asm/msr.h>
>  #include "speedstep-lib.h"
> +#include <linux/ctype.h>
>  
>  #define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "speedstep-lib", msg)
>  
> @@ -151,7 +152,40 @@ static unsigned int pentium_core_get_fre
>  
>  	return (msr_tmp * fsb);
>  }
> -
> +/* When Model_id is less than 2, the FSB ratio is
> +obtained from the string of model_id */
> +static unsigned int p4_01_get_fsb_ratio(void)
> +{
> +	struct cpuinfo_x86 *c = &boot_cpu_data;
> +	unsigned int fsb_m;
> +	char model_id[64];
> +	unsigned int  freq_mhz;
> +	unsigned int max_ratio;
> +	char *ptr;
> +	int i = 0;
> +
> +	ptr = model_id;
> +	strncpy(ptr, c->x86_model_id, strlen(c->x86_model_id));
> +	for (i = 0; i < strlen(model_id); i++)
> +		model_id[i] = tolower(model_id[i]);
> +	if (strstr(model_id, "mhz"))
> +		fsb_m = 100;
> +	else
> +		fsb_m = 0;
> +	if (!fsb_m) {
> +		printk(KERN_DEBUG "CPU doesn't support speedstep\n");
> +		return 0;
> +	}
> +	ptr = strstr(model_id, "hz");
> +	if (ptr)
> +		*ptr = '\0';
> +	freq_mhz = 0;
> +	ptr = strrchr(model_id, ' ');
> +	if (ptr)
> +		sscanf(ptr, "%d", &freq_mhz);
> +	max_ratio = freq_mhz / fsb_m;
> +	return max_ratio;
> +}
>  
>  static unsigned int pentium4_get_frequency(void)
>  {
> @@ -189,8 +223,10 @@ static unsigned int pentium4_get_frequen
>  		printk(KERN_DEBUG "speedstep-lib: couldn't detect FSB speed. Please send an e-mail to <linux@brodo.de>\n");
>  
>  	/* Multiplier. */
> +	/* if Model is less than 2 , the ratio is obtained from the
> +	 * string of model_id */
>  	if (c->x86_model < 2)
> -		mult = msr_lo >> 27;
> +		mult = p4_01_get_fsb_ratio();
>  	else
>  		mult = msr_lo >> 24;
>  

I'm not excited about adding code to parse the model string,
particularly when the justification is an early P4 model that
doesn't even support P-states.

I'd prefer to see p4-clockmod deleted from the kernel.

-Len