Ack: [Precise SRU PATCH 2/3] hwmon: (fam15h_power) Increase output resolution

[Brad Figg]

On 06/13/2012 01:52 PM, Tim Gardner wrote:
> From: Andre Przywara <andre.przywara at amd.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1009086
> 
> On high CPU load the accumulating values in the running_avg_cap
> register are very low (below 10), so averaging them too early leads
> to unnecessary poor output resolution. Since we pretend to output
> micro-Watt we better keep all the bits we have as long as possible.
> 
> Signed-off-by: Andre Przywara <andre.przywara at amd.com>
> Signed-off-by: Andreas Herrmann <andreas.herrmann3 at amd.com>
> Acked-by: Guenter Roeck <guenter.roeck at ericsson.com>
> Signed-off-by: Jean Delvare <khali at linux-fr.org>
> (cherry picked from commit 941a956b0e387b21f385f486c34ef67576775cfc)
> 
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
> ---
>  drivers/hwmon/fam15h_power.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c
> index 930370d..b7494af 100644
> --- a/drivers/hwmon/fam15h_power.c
> +++ b/drivers/hwmon/fam15h_power.c
> @@ -61,14 +61,14 @@ static ssize_t show_power(struct device *dev,
>  				  REG_TDP_RUNNING_AVERAGE, &val);
>  	running_avg_capture = (val >> 4) & 0x3fffff;
>  	running_avg_capture = sign_extend32(running_avg_capture, 21);
> -	running_avg_range = val & 0xf;
> +	running_avg_range = (val & 0xf) + 1;
>  
>  	pci_bus_read_config_dword(f4->bus, PCI_DEVFN(PCI_SLOT(f4->devfn), 5),
>  				  REG_TDP_LIMIT3, &val);
>  
>  	tdp_limit = val >> 16;
> -	curr_pwr_watts = tdp_limit + data->base_tdp -
> -		(s32)(running_avg_capture >> (running_avg_range + 1));
> +	curr_pwr_watts = (tdp_limit + data->base_tdp) << running_avg_range;
> +	curr_pwr_watts -= running_avg_capture;
>  	curr_pwr_watts *= data->tdp_to_watts;
>  
>  	/*
> @@ -78,7 +78,7 @@ static ssize_t show_power(struct device *dev,
>  	 * scaling factor 1/(2^16).  For conversion we use
>  	 * (10^6)/(2^16) = 15625/(2^10)
>  	 */
> -	curr_pwr_watts = (curr_pwr_watts * 15625) >> 10;
> +	curr_pwr_watts = (curr_pwr_watts * 15625) >> (10 + running_avg_range);
>  	return sprintf(buf, "%u\n", (unsigned int) curr_pwr_watts);
>  }
>  static DEVICE_ATTR(power1_input, S_IRUGO, show_power, NULL);


-- 
Brad Figg brad.figg at canonical.com http://www.canonical.com