[PATCH]: cpufreq: pcc-cpufreq: don't load driver if get_freq fails during init.

[PATCH]: cpufreq: pcc-cpufreq: don't load driver if get_freq fails during init.

[Naga Chumbalkar]

Return 0 on failure. This will cause the initialization of the driver
to fail and prevent the driver from loading if the BIOS cannot handle
the PCC interface command to "get frequency". Otherwise, the driver
will load and display a very high value like "4294967274" (which is
actually -EINVAL) for frequency:

# cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
4294967274

Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
---

diff --git a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
index 4f6f679..4a5a42b 100644
--- a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
+++ b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
@@ -195,7 +195,7 @@ static unsigned int pcc_get_freq(unsigned int cpu)
 cmd_incomplete:
 	iowrite16(0, &pcch_hdr->status);
 	spin_unlock(&pcc_lock);
-	return -EINVAL;
+	return 0;
 }
 
 static int pcc_cpufreq_target(struct cpufreq_policy *policy,

Re: [PATCH]: cpufreq: pcc-cpufreq: don't load driver if get_freq fails during init.

[Thomas Renninger]

Good catch.

On Wednesday, March 09, 2011 03:02:49 PM Naga Chumbalkar wrote:
> 
> Return 0 on failure. This will cause the initialization of the driver
> to fail and prevent the driver from loading if the BIOS cannot handle
> the PCC interface command to "get frequency". Otherwise, the driver
> will load and display a very high value like "4294967274" (which is
> actually -EINVAL) for frequency:
> 
> # cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
> 4294967274
> 
> Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Reviewed-by: Thomas Renninger <trenn@suse.de>

While this is not a regression, it's an easy fix.
It should make sense to add:
CC: stable@kernel.org
?

   Thomas
> ---
> 
> diff --git a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c 
b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
> index 4f6f679..4a5a42b 100644
> --- a/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
> +++ b/arch/x86/kernel/cpu/cpufreq/pcc-cpufreq.c
> @@ -195,7 +195,7 @@ static unsigned int pcc_get_freq(unsigned int cpu)
>  cmd_incomplete:
>  	iowrite16(0, &pcch_hdr->status);
>  	spin_unlock(&pcc_lock);
> -	return -EINVAL;
> +	return 0;
>  }
>  
>  static int pcc_cpufreq_target(struct cpufreq_policy *policy,
> --
> To unsubscribe from this list: send the line "unsubscribe cpufreq" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: [PATCH]: cpufreq: pcc-cpufreq: don't load driver if get_freq fails during init.

[Greg KH]

On Wed, Mar 09, 2011 at 05:09:40PM +0100, Thomas Renninger wrote:
> Good catch.
> 
> On Wednesday, March 09, 2011 03:02:49 PM Naga Chumbalkar wrote:
> > 
> > Return 0 on failure. This will cause the initialization of the driver
> > to fail and prevent the driver from loading if the BIOS cannot handle
> > the PCC interface command to "get frequency". Otherwise, the driver
> > will load and display a very high value like "4294967274" (which is
> > actually -EINVAL) for frequency:
> > 
> > # cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
> > 4294967274
> > 
> > Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
> Reviewed-by: Thomas Renninger <trenn@suse.de>
> 
> While this is not a regression, it's an easy fix.
> It should make sense to add:
> CC: stable@kernel.org
> ?

Yes you should :)

thanks,

greg k-h