Re: [PATCH/RFT] thermal: rcar_gen3_thermal: Update calculation formula due to HW evaluation

[Simon Horman <horms@verge.net.au>]

On Fri, Mar 22, 2019 at 05:47:53AM +0900, Yoshihiro Kaneko wrote:
> From: Dien Pham <dien.pham.ry@renesas.com>
> 
> 1/ As evaluation of hardware team, temperature calculation formula
>  of M3-W is difference from all other SoCs as below:
>  - M3-W: Tj_1: 116 (so Tj_1 - Tj_3 = 157)
>  - Others: Tj_1: 126 (so Tj_1 - Tj_3 = 167)
> 
> 2/ Update the formula to calculate CTEMP:
>   Currently, the CTEMP is average of val1 (is calculated by
>   formula 1) and val2 (is calculated by formula 2). But,
>   as description in HWM (chapter 10A.3.1.1 Setting of Normal Mode)
> 
>   If (STEMP < Tj_T) CTEMP value should be val1.
>   If (STEMP > Tj_T) CTEMP value should be val2.
> 
> 3/ Update the formula to calculate temperature:
>   Currently, current TEMP is calculated as
>   average of val1 (is calculated by formula 1)
>   and val2 (is calculated by formula 2). But,
>   as description in HWM (chapter 10A.3.1.2 Normal Mode.)
> 
>   If (TEMP_CODE < THCODE2[11:0]) CTEMP value should be val1.
>   If (TEMP_CODE > THCODE2[11:0]) CTEMP value should be val2.
> 
> Signed-off-by: Dien Pham <dien.pham.ry@renesas.com>
> [ykaneko0929@gmail.com: use the data field of the of_device_id for Tj_1]
> [ykaneko0929@gmail.com: revise a description of case 1 of the commit log]
> Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>

I'm wondering if we could split this up into three patches,
one for each problem it solves? Partly because I think it is good to fix
one problem per patch. And partly because am having trouble
verifying this patch - the new if statement in rcar_gen3_thermal_get_temp()
seems to result in 0 temperature readings when the else case is used.

> ---
>  drivers/thermal/rcar_gen3_thermal.c | 86 +++++++++++++++++++++++++------------
>  1 file changed, 58 insertions(+), 28 deletions(-)
> 
> This patch is based on the master branch of Linus Torvalds's linux tree.
> 
> diff --git a/drivers/thermal/rcar_gen3_thermal.c b/drivers/thermal/rcar_gen3_thermal.c
> index 88fa41c..de6f244 100644
> --- a/drivers/thermal/rcar_gen3_thermal.c
> +++ b/drivers/thermal/rcar_gen3_thermal.c
> @@ -63,6 +63,15 @@
>  
>  #define TSC_MAX_NUM	3
>  
> +static int tj_2;

We need to avoid global variables. There can be multiple
instances of this driver. (Although they will all get the same
value for tj_2.

Perhaps it can be added to struct rcar_gen3_thermal_tsc?

...