Re: [lm-sensors] [PATCH] hwmon: (coretemp) Do not return -EAGAIN for low temperatures

[Guenter Roeck <linux@roeck-us.net>]

On Sat, Dec 07, 2013 at 10:05:57AM -0800, Guenter Roeck wrote:
> Some Intel CPUs do not set the 'valid' bit in IA32_THERM_STATUS if the
> temperature is too low to be measured. This condition will not change until
> the CPU is hot enough for its temperature to be measured. Returning an error
> in such conditions is not very useful. Drop checking the valid bit and just
> return the reported temperature instead.
> 
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> I don't think we ever closed on this. Giving it a shot.
> 
No feedback. This will go into 3.14 unless there are objections.

Guenter

>  drivers/hwmon/coretemp.c |   17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index 310ce19..6e0579e 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -177,18 +177,19 @@ static ssize_t show_temp(struct device *dev,
>  	/* Check whether the time interval has elapsed */
>  	if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
>  		rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
> -		tdata->valid = 0;
> -		/* Check whether the data is valid */
> -		if (eax & 0x80000000) {
> -			tdata->temp = tdata->tjmax -
> -					((eax >> 16) & 0x7f) * 1000;
> -			tdata->valid = 1;
> -		}
> +		/*
> +		 * Ignore the valid bit. In all observed cases the register
> +		 * value is either low or zero if the valid bit is 0.
> +		 * Return it instead of reporting an error which doesn't
> +		 * really help at all.
> +		 */
> +		tdata->temp = tdata->tjmax - ((eax >> 16) & 0x7f) * 1000;
> +		tdata->valid = 1;
>  		tdata->last_updated = jiffies;
>  	}
>  
>  	mutex_unlock(&tdata->update_lock);
> -	return tdata->valid ? sprintf(buf, "%d\n", tdata->temp) : -EAGAIN;
> +	return sprintf(buf, "%d\n", tdata->temp);
>  }
>  
>  struct tjmax_pci {
> -- 
> 1.7.9.7
> 
> 

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