| Message ID | 20220401214032.3738095-2-michael@walle.cc (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | hwmon: add lan9668 driver | expand |
On Fri, Apr 01, 2022 at 11:40:29PM +0200, 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> > Reviewed-by: Guenter Roeck <linux@roeck-us.net> Applied to hwmon-next. 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");
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");