Re: [PATCH] hwmon: corsair-psu: update calculation of LINEAR11 values

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

On Sat, Feb 27, 2021 at 10:34:42AM +0100, Wilken Gottwalt wrote:
> Changes the way how LINEAR11 values are calculated. The new method
> increases the precision of 2-3 digits.
> 
> old method:
> 	corsairpsu-hid-3-1
> 	Adapter: HID adapter
> 	v_in:        230.00 V
> 	v_out +12v:   12.00 V
> 	v_out +5v:     5.00 V
> 	v_out +3.3v:   3.00 V
> 	psu fan:        0 RPM
> 	vrm temp:     +44.0°C
> 	case temp:    +37.0°C
> 	power total: 152.00 W
> 	power +12v:  112.00 W
> 	power +5v:    38.00 W
> 	power +3.3v:   5.00 W
> 	curr in:          N/A
> 	curr +12v:     9.00 A
> 	curr +5v:      7.00 A
> 	curr +3.3v:  1000.00 mA
> 
> new method:
> 	corsairpsu-hid-3-1
> 	Adapter: HID adapter
> 	v_in:        230.00 V
> 	v_out +12v:   12.16 V
> 	v_out +5v:     5.01 V
> 	v_out +3.3v:   3.30 V
> 	psu fan:        0 RPM
> 	vrm temp:     +44.5°C
> 	case temp:    +37.8°C
> 	power total: 148.00 W
> 	power +12v:  108.00 W
> 	power +5v:    37.00 W
> 	power +3.3v:   4.50 W
> 	curr in:          N/A
> 	curr +12v:     9.25 A
> 	curr +5v:      7.50 A
> 	curr +3.3v:    1.50 A
> 
> Co-developed-by: Jack Doan <me@jackdoan.com>
> Signed-off-by: Jack Doan <me@jackdoan.com>
> Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/corsair-psu.c | 30 ++++++++----------------------
>  1 file changed, 8 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/hwmon/corsair-psu.c b/drivers/hwmon/corsair-psu.c
> index 99494056f4bd..b0953eeeb2d3 100644
> --- a/drivers/hwmon/corsair-psu.c
> +++ b/drivers/hwmon/corsair-psu.c
> @@ -119,27 +119,13 @@ struct corsairpsu_data {
>  };
>  
>  /* some values are SMBus LINEAR11 data which need a conversion */
> -static int corsairpsu_linear11_to_int(const int val)
> +static int corsairpsu_linear11_to_int(const u16 val, const int scale)
>  {
> -	int exp = (val & 0xFFFF) >> 0x0B;
> -	int mant = val & 0x7FF;
> -	int i;
> -
> -	if (exp > 0x0F)
> -		exp -= 0x20;
> -	if (mant > 0x3FF)
> -		mant -= 0x800;
> -	if ((mant & 0x01) == 1)
> -		++mant;
> -	if (exp < 0) {
> -		for (i = 0; i < -exp; ++i)
> -			mant /= 2;
> -	} else {
> -		for (i = 0; i < exp; ++i)
> -			mant *= 2;
> -	}
> +	const int exp = ((s16)val) >> 11;
> +	const int mant = (((s16)(val & 0x7ff)) << 5) >> 5;
> +	const int result = mant * scale;
>  
> -	return mant;
> +	return (exp >= 0) ? (result << exp) : (result >> -exp);
>  }
>  
>  static int corsairpsu_usb_cmd(struct corsairpsu_data *priv, u8 p0, u8 p1, u8 p2, void *data)
> @@ -249,14 +235,14 @@ static int corsairpsu_get_value(struct corsairpsu_data *priv, u8 cmd, u8 rail, l
>  	case PSU_CMD_RAIL_AMPS:
>  	case PSU_CMD_TEMP0:
>  	case PSU_CMD_TEMP1:
> -		*val = corsairpsu_linear11_to_int(tmp & 0xFFFF) * 1000;
> +		*val = corsairpsu_linear11_to_int(tmp & 0xFFFF, 1000);
>  		break;
>  	case PSU_CMD_FAN:
> -		*val = corsairpsu_linear11_to_int(tmp & 0xFFFF);
> +		*val = corsairpsu_linear11_to_int(tmp & 0xFFFF, 1);
>  		break;
>  	case PSU_CMD_RAIL_WATTS:
>  	case PSU_CMD_TOTAL_WATTS:
> -		*val = corsairpsu_linear11_to_int(tmp & 0xFFFF) * 1000000;
> +		*val = corsairpsu_linear11_to_int(tmp & 0xFFFF, 1000000);
>  		break;
>  	case PSU_CMD_TOTAL_UPTIME:
>  	case PSU_CMD_UPTIME: