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[1/2] thermal: kirkwood: Fix thermal sensor formula

Message ID 1363954983-30822-2-git-send-email-ezequiel.garcia@free-electrons.com (mailing list archive)
State New, archived
Headers show

Commit Message

Ezequiel Garcia March 22, 2013, 12:23 p.m. UTC 
The currently formula has been taken from the 88AP510 SoC datasheet,
which is not exactly correct. The correct value for the temperature
in Celcius of the sensor present in this SoC is:

  Celsius = (322-reg)/1.3625

Signed-off-by: Lior Amsalem <alior@marvell.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
---
 drivers/thermal/kirkwood_thermal.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

Comments

Zhang Rui March 26, 2013, 2:24 p.m. UTC | #1 
On Fri, 2013-03-22 at 09:23 -0300, Ezequiel Garcia wrote:
> The currently formula has been taken from the 88AP510 SoC datasheet,
> which is not exactly correct. The correct value for the temperature
> in Celcius of the sensor present in this SoC is:
> 
>   Celsius = (322-reg)/1.3625
> 
> Signed-off-by: Lior Amsalem <alior@marvell.com>
> Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>

applied to thermal -next.

thanks,
rui
> ---
>  drivers/thermal/kirkwood_thermal.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/thermal/kirkwood_thermal.c b/drivers/thermal/kirkwood_thermal.c
> index 65cb4f0..84b331f 100644
> --- a/drivers/thermal/kirkwood_thermal.c
> +++ b/drivers/thermal/kirkwood_thermal.c
> @@ -49,13 +49,13 @@ static int kirkwood_get_temp(struct thermal_zone_device *thermal,
>  	}
>  
>  	/*
> -	 * Calculate temperature. See Section 8.10.1 of the 88AP510,
> -	 * datasheet, which has the same sensor.
> -	 * Documentation/arm/Marvell/README
> +	 * Calculate temperature. According to Marvell internal
> +	 * documentation the formula for this is:
> +	 * Celsius = (322-reg)/1.3625
>  	 */
>  	reg = (reg >> KIRKWOOD_THERMAL_TEMP_OFFSET) &
>  		KIRKWOOD_THERMAL_TEMP_MASK;
> -	*temp = ((2281638UL - (7298*reg)) / 10);
> +	*temp = ((3220000000UL - (10000000UL * reg)) / 13625);
>  
>  	return 0;
>  }
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Patch

diff --git a/drivers/thermal/kirkwood_thermal.c b/drivers/thermal/kirkwood_thermal.c
index 65cb4f0..84b331f 100644
--- a/drivers/thermal/kirkwood_thermal.c
+++ b/drivers/thermal/kirkwood_thermal.c
@@ -49,13 +49,13 @@  static int kirkwood_get_temp(struct thermal_zone_device *thermal,
 	}
 
 	/*
-	 * Calculate temperature. See Section 8.10.1 of the 88AP510,
-	 * datasheet, which has the same sensor.
-	 * Documentation/arm/Marvell/README
+	 * Calculate temperature. According to Marvell internal
+	 * documentation the formula for this is:
+	 * Celsius = (322-reg)/1.3625
 	 */
 	reg = (reg >> KIRKWOOD_THERMAL_TEMP_OFFSET) &
 		KIRKWOOD_THERMAL_TEMP_MASK;
-	*temp = ((2281638UL - (7298*reg)) / 10);
+	*temp = ((3220000000UL - (10000000UL * reg)) / 13625);
 
 	return 0;
 }