| Message ID | 20220328112505.3025374-1-michael@walle.cc |
|---|---|
| Headers | show |
| Series | hwmon: add lan9668 driver | expand |
On 3/28/22 04:25, Michael Walle wrote: > Some temperature and voltage sensors use a polynomial to convert between > raw data points and actual temperature or voltage. The polynomial is > usually the result of a curve fitting of the diode characteristic. > > The BT1 PVT hwmon driver already uses such a polynonmial calculation > which is rather generic. Move it to lib/ so other drivers can reuse it. > > Signed-off-by: Michael Walle <michael@walle.cc> For my reference: Reviewed-by: Guenter Roeck <linux@roeck-us.net> I don't see who owns lib/, so I'll just take this patch through hwmon unless someone objects. Thanks, Guenter > --- > include/linux/polynomial.h | 35 ++++++++++++ > lib/Kconfig | 3 ++ > lib/Makefile | 2 + > lib/polynomial.c | 108 +++++++++++++++++++++++++++++++++++++ > 4 files changed, 148 insertions(+) > create mode 100644 include/linux/polynomial.h > create mode 100644 lib/polynomial.c > > diff --git a/include/linux/polynomial.h b/include/linux/polynomial.h > new file mode 100644 > index 000000000000..9e074a0bb6fa > --- /dev/null > +++ b/include/linux/polynomial.h > @@ -0,0 +1,35 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC > + */ > + > +#ifndef _POLYNOMIAL_H > +#define _POLYNOMIAL_H > + > +/* > + * struct polynomial_term - one term descriptor of a polynomial > + * @deg: degree of the term. > + * @coef: multiplication factor of the term. > + * @divider: distributed divider per each degree. > + * @divider_leftover: divider leftover, which couldn't be redistributed. > + */ > +struct polynomial_term { > + unsigned int deg; > + long coef; > + long divider; > + long divider_leftover; > +}; > + > +/* > + * struct polynomial - a polynomial descriptor > + * @total_divider: total data divider. > + * @terms: polynomial terms, last term must have degree of 0 > + */ > +struct polynomial { > + long total_divider; > + struct polynomial_term terms[]; > +}; > + > +long polynomial_calc(const struct polynomial *poly, long data); > + > +#endif > diff --git a/lib/Kconfig b/lib/Kconfig > index 087e06b4cdfd..6a843639814f 100644 > --- a/lib/Kconfig > +++ b/lib/Kconfig > @@ -737,3 +737,6 @@ config PLDMFW > > config ASN1_ENCODER > tristate > + > +config POLYNOMIAL > + tristate > diff --git a/lib/Makefile b/lib/Makefile > index 6b9ffc1bd1ee..89fcae891361 100644 > --- a/lib/Makefile > +++ b/lib/Makefile > @@ -263,6 +263,8 @@ obj-$(CONFIG_MEMREGION) += memregion.o > obj-$(CONFIG_STMP_DEVICE) += stmp_device.o > obj-$(CONFIG_IRQ_POLL) += irq_poll.o > > +obj-$(CONFIG_POLYNOMIAL) += polynomial.o > + > # stackdepot.c should not be instrumented or call instrumented functions. > # Prevent the compiler from calling builtins like memcmp() or bcmp() from this > # file. > diff --git a/lib/polynomial.c b/lib/polynomial.c > new file mode 100644 > index 000000000000..66d383445fec > --- /dev/null > +++ b/lib/polynomial.c > @@ -0,0 +1,108 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Generic polynomial calculation using integer coefficients. > + * > + * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC > + * > + * Authors: > + * Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru> > + * Serge Semin <Sergey.Semin@baikalelectronics.ru> > + * > + */ > + > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/polynomial.h> > + > +/* > + * Originally this was part of drivers/hwmon/bt1-pvt.c. > + * There the following conversion is used and should serve as an example here: > + * > + * The original translation formulae of the temperature (in degrees of Celsius) > + * to PVT data and vice-versa are following: > + * > + * N = 1.8322e-8*(T^4) + 2.343e-5*(T^3) + 8.7018e-3*(T^2) + 3.9269*(T^1) + > + * 1.7204e2 > + * T = -1.6743e-11*(N^4) + 8.1542e-8*(N^3) + -1.8201e-4*(N^2) + > + * 3.1020e-1*(N^1) - 4.838e1 > + * > + * where T = [-48.380, 147.438]C and N = [0, 1023]. > + * > + * They must be accordingly altered to be suitable for the integer arithmetics. > + * The technique is called 'factor redistribution', which just makes sure the > + * multiplications and divisions are made so to have a result of the operations > + * within the integer numbers limit. In addition we need to translate the > + * formulae to accept millidegrees of Celsius. Here what they look like after > + * the alterations: > + * > + * N = (18322e-20*(T^4) + 2343e-13*(T^3) + 87018e-9*(T^2) + 39269e-3*T + > + * 17204e2) / 1e4 > + * T = -16743e-12*(D^4) + 81542e-9*(D^3) - 182010e-6*(D^2) + 310200e-3*D - > + * 48380 > + * where T = [-48380, 147438] mC and N = [0, 1023]. > + * > + * static const struct polynomial poly_temp_to_N = { > + * .total_divider = 10000, > + * .terms = { > + * {4, 18322, 10000, 10000}, > + * {3, 2343, 10000, 10}, > + * {2, 87018, 10000, 10}, > + * {1, 39269, 1000, 1}, > + * {0, 1720400, 1, 1} > + * } > + * }; > + * > + * static const struct polynomial poly_N_to_temp = { > + * .total_divider = 1, > + * .terms = { > + * {4, -16743, 1000, 1}, > + * {3, 81542, 1000, 1}, > + * {2, -182010, 1000, 1}, > + * {1, 310200, 1000, 1}, > + * {0, -48380, 1, 1} > + * } > + * }; > + */ > + > +/** > + * polynomial_calc - calculate a polynomial using integer arithmetic > + * > + * @poly: pointer to the descriptor of the polynomial > + * @data: input value of the polynimal > + * > + * Calculate the result of a polynomial using only integer arithmetic. For > + * this to work without too much loss of precision the coefficients has to > + * be altered. This is called factor redistribution. > + * > + * Returns the result of the polynomial calculation. > + */ > +long polynomial_calc(const struct polynomial *poly, long data) > +{ > + const struct polynomial_term *term = poly->terms; > + long total_divider = poly->total_divider ?: 1; > + long tmp, ret = 0; > + int deg; > + > + /* > + * 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. > + */ > + 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 / total_divider; > +} > +EXPORT_SYMBOL_GPL(polynomial_calc); > + > +MODULE_DESCRIPTION("Generic polynomial calculations"); > +MODULE_LICENSE("GPL");
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; > }