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Message-ID: <2fbefb5f-a53c-ea68-0a1d-90c60f90d667@roeck-us.net>
Date:   Wed, 30 Mar 2022 12:59:59 -0700
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Subject: Re: [PATCH v2 2/4] hwmon: (bt1-pvt) use generic polynomial functions
Content-Language: en-US
To:     Michael Walle <michael@walle.cc>, Jean Delvare <jdelvare@suse.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc:     linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220328112505.3025374-1-michael@walle.cc>
 <20220328112505.3025374-3-michael@walle.cc>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <20220328112505.3025374-3-michael@walle.cc>
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On 3/28/22 04:25, Michael Walle wrote:
> The polynomial calculation function was moved into lib/ to be able to
> reuse it. Move over to this one.
> 
> Signed-off-by: Michael Walle <michael@walle.cc>

For my reference:

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>   drivers/hwmon/Kconfig   |  1 +
>   drivers/hwmon/bt1-pvt.c | 50 +++++++++++------------------------------
>   2 files changed, 14 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 68a8a27ab3b7..be9773270e53 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -415,6 +415,7 @@ config SENSORS_ATXP1
>   config SENSORS_BT1_PVT
>   	tristate "Baikal-T1 Process, Voltage, Temperature sensor driver"
>   	depends on MIPS_BAIKAL_T1 || COMPILE_TEST
> +	select POLYNOMIAL
>   	help
>   	  If you say yes here you get support for Baikal-T1 PVT sensor
>   	  embedded into the SoC.
> diff --git a/drivers/hwmon/bt1-pvt.c b/drivers/hwmon/bt1-pvt.c
> index 74ce5211eb75..21ab172774ec 100644
> --- a/drivers/hwmon/bt1-pvt.c
> +++ b/drivers/hwmon/bt1-pvt.c
> @@ -26,6 +26,7 @@
>   #include <linux/mutex.h>
>   #include <linux/of.h>
>   #include <linux/platform_device.h>
> +#include <linux/polynomial.h>
>   #include <linux/seqlock.h>
>   #include <linux/sysfs.h>
>   #include <linux/types.h>
> @@ -65,7 +66,7 @@ static const struct pvt_sensor_info pvt_info[] = {
>    *     48380,
>    * where T = [-48380, 147438] mC and N = [0, 1023].
>    */
> -static const struct pvt_poly __maybe_unused poly_temp_to_N = {
> +static const struct polynomial __maybe_unused poly_temp_to_N = {
>   	.total_divider = 10000,
>   	.terms = {
>   		{4, 18322, 10000, 10000},
> @@ -76,7 +77,7 @@ static const struct pvt_poly __maybe_unused poly_temp_to_N = {
>   	}
>   };
>   
> -static const struct pvt_poly poly_N_to_temp = {
> +static const struct polynomial poly_N_to_temp = {
>   	.total_divider = 1,
>   	.terms = {
>   		{4, -16743, 1000, 1},
> @@ -97,7 +98,7 @@ static const struct pvt_poly poly_N_to_temp = {
>    * N = (18658e-3*V - 11572) / 10,
>    * V = N * 10^5 / 18658 + 11572 * 10^4 / 18658.
>    */
> -static const struct pvt_poly __maybe_unused poly_volt_to_N = {
> +static const struct polynomial __maybe_unused poly_volt_to_N = {
>   	.total_divider = 10,
>   	.terms = {
>   		{1, 18658, 1000, 1},
> @@ -105,7 +106,7 @@ static const struct pvt_poly __maybe_unused poly_volt_to_N = {
>   	}
>   };
>   
> -static const struct pvt_poly poly_N_to_volt = {
> +static const struct polynomial poly_N_to_volt = {
>   	.total_divider = 10,
>   	.terms = {
>   		{1, 100000, 18658, 1},
> @@ -113,31 +114,6 @@ static const struct pvt_poly poly_N_to_volt = {
>   	}
>   };
>   
> -/*
> - * Here is the polynomial calculation function, which performs the
> - * redistributed terms calculations. It's pretty straightforward. We walk
> - * over each degree term up to the free one, and perform the redistributed
> - * multiplication of the term coefficient, its divider (as for the rationale
> - * fraction representation), data power and the rational fraction divider
> - * leftover. Then all of this is collected in a total sum variable, which
> - * value is normalized by the total divider before being returned.
> - */
> -static long pvt_calc_poly(const struct pvt_poly *poly, long data)
> -{
> -	const struct pvt_poly_term *term = poly->terms;
> -	long tmp, ret = 0;
> -	int deg;
> -
> -	do {
> -		tmp = term->coef;
> -		for (deg = 0; deg < term->deg; ++deg)
> -			tmp = mult_frac(tmp, data, term->divider);
> -		ret += tmp / term->divider_leftover;
> -	} while ((term++)->deg);
> -
> -	return ret / poly->total_divider;
> -}
> -
>   static inline u32 pvt_update(void __iomem *reg, u32 mask, u32 data)
>   {
>   	u32 old;
> @@ -324,9 +300,9 @@ static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
>   	} while (read_seqretry(&cache->data_seqlock, seq));
>   
>   	if (type == PVT_TEMP)
> -		*val = pvt_calc_poly(&poly_N_to_temp, data);
> +		*val = polynomial_calc(&poly_N_to_temp, data);
>   	else
> -		*val = pvt_calc_poly(&poly_N_to_volt, data);
> +		*val = polynomial_calc(&poly_N_to_volt, data);
>   
>   	return 0;
>   }
> @@ -345,9 +321,9 @@ static int pvt_read_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
>   		data = FIELD_GET(PVT_THRES_HI_MASK, data);
>   
>   	if (type == PVT_TEMP)
> -		*val = pvt_calc_poly(&poly_N_to_temp, data);
> +		*val = polynomial_calc(&poly_N_to_temp, data);
>   	else
> -		*val = pvt_calc_poly(&poly_N_to_volt, data);
> +		*val = polynomial_calc(&poly_N_to_volt, data);
>   
>   	return 0;
>   }
> @@ -360,10 +336,10 @@ static int pvt_write_limit(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
>   
>   	if (type == PVT_TEMP) {
>   		val = clamp(val, PVT_TEMP_MIN, PVT_TEMP_MAX);
> -		data = pvt_calc_poly(&poly_temp_to_N, val);
> +		data = polynomial_calc(&poly_temp_to_N, val);
>   	} else {
>   		val = clamp(val, PVT_VOLT_MIN, PVT_VOLT_MAX);
> -		data = pvt_calc_poly(&poly_volt_to_N, val);
> +		data = polynomial_calc(&poly_volt_to_N, val);
>   	}
>   
>   	/* Serialize limit update, since a part of the register is changed. */
> @@ -522,9 +498,9 @@ static int pvt_read_data(struct pvt_hwmon *pvt, enum pvt_sensor_type type,
>   		return -ETIMEDOUT;
>   
>   	if (type == PVT_TEMP)
> -		*val = pvt_calc_poly(&poly_N_to_temp, data);
> +		*val = polynomial_calc(&poly_N_to_temp, data);
>   	else
> -		*val = pvt_calc_poly(&poly_N_to_volt, data);
> +		*val = polynomial_calc(&poly_N_to_volt, data);
>   
>   	return 0;
>   }