linux-kernel - Re: [PATCH 1/2 V2] hwmon: (coretemp) Detect the thermal sensors by CPUID

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Date:	Mon, 10 May 2010 08:45:51 -0400
From:	Valdis.Kletnieks@...edu
To:	Huaxu Wan <huaxu.wan@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org,
	huaxu.wan@...el.com, Carsten Emde <Carsten.Emde@...dl.org>
Subject: Re: [PATCH 1/2 V2] hwmon: (coretemp) Detect the thermal sensors by CPUID

On Mon, 10 May 2010 11:35:25 +0800, Huaxu Wan said:
> 
> The thermal sensors of Intel(R) CPUs can be detected by CPUID instruction,
> indicated by CPUID.06H.EAX[0].
> 
> Signed-off-by: Huaxu Wan <huaxu.wan@...ux.intel.com>
> Signed-off-by: Carsten Emde <C.Emde@...dl.org>
> ---
>  drivers/hwmon/coretemp.c |   24 +++++++-----------------
>  1 files changed, 7 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index e9b7fbc..d194207 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -440,6 +440,7 @@ static int __init coretemp_init(void)
>  {
>  	int i, err = -ENODEV;
>  	struct pdev_entry *p, *n;
> +	u32 eax;
>  
>  	/* quick check if we run Intel */
>  	if (cpu_data(0).x86_vendor != X86_VENDOR_INTEL)
> @@ -450,23 +451,12 @@ static int __init coretemp_init(void)
>  		goto exit;
>  
>  	for_each_online_cpu(i) {
> -		struct cpuinfo_x86 *c = &cpu_data(i);
> -
> -		/* check if family 6, models 0xe (Pentium M DC),
> -		  0xf (Core 2 DC 65nm), 0x16 (Core 2 SC 65nm),
> -		  0x17 (Penryn 45nm), 0x1a (Nehalem), 0x1c (Atom),
> -		  0x1e (Lynnfield) */
> -		if ((c->cpuid_level < 0) || (c->x86 != 0x6) ||
> -		    !((c->x86_model == 0xe) || (c->x86_model == 0xf) ||
> -			(c->x86_model == 0x16) || (c->x86_model == 0x17) ||
> -			(c->x86_model == 0x1a) || (c->x86_model == 0x1c) ||
> -			(c->x86_model == 0x1e))) {

So we remove something that checks the CPU level for a model we *expect*
to find a thermal sensor, and only throws a KERN_WARNING if we're on a
model we don't know about...

> + 		/* check if the CPU has thermal sensor */
> + 		eax = cpuid_eax(0x06);
> + 		if (!(eax & 0x01)) {
> + 			struct cpuinfo_x86 *c = &cpu_data(i);
> + 			printk(KERN_WARNING DRVNAME ": CPU (model=0x%x)"
> + 				" has no thermal sensor!\n", c->x86_model);

And replace it with a totally unprotected check that's going to fire off
a KERN_WARNING on every single CPU that Intel ever made that doesn't
include a hardware thermal sensor - including all the family 0-5,
and model < 0x0e hardware.

KERN_WARNING is for "We expected to find the hardware but it's gone off
for a walk on us".  If you wanted to say "Hmm.. this CPU doesn't have one"
you probably wanted KERN_DEBUG or *maybe* KERN_INFO.

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