From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F3B6C433EF for ; Mon, 2 May 2022 04:32:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383208AbiEBEgK (ORCPT ); Mon, 2 May 2022 00:36:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239852AbiEBEgG (ORCPT ); Mon, 2 May 2022 00:36:06 -0400 Received: from mail-oi1-x235.google.com (mail-oi1-x235.google.com [IPv6:2607:f8b0:4864:20::235]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3BF134B84; Sun, 1 May 2022 21:32:38 -0700 (PDT) Received: by mail-oi1-x235.google.com with SMTP id r1so14063182oie.4; Sun, 01 May 2022 21:32:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=AW4eMMP+xh3LI9RUDK7+BuPWS9twmc/v2jOzuayztXg=; b=G4v2c7qA5HwE5n1Z7Ta6+BHv0tLCxmjz2lMIEnFv4vgIHkVzSYQ6adjG1/htq34tHn 4qYJvmQFgH1bvq6oA+lJqZiEAc45euNBZpNnNsFgN+i6SmrHaHs++RyPxKO8gJGcpLZg 5PmbBYq/nIm58TBX88PfFachu9m5wLLUxc8UbN0jGcN7HxiRfF/RcU+zo1jDtoUkBVjC /CglZ07lEeGBhYwtGaRhHItlgceZBiEHKk49eTs7fvvsEmgG77m+SimAK/cPq8qIFLSr 8BSm8H4HYfihSB0RPk59L9ntj3qK1nc9egsk9hmzkhf0tnvqvX6EpOi002p9msAHxNAa PWbA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=AW4eMMP+xh3LI9RUDK7+BuPWS9twmc/v2jOzuayztXg=; b=Z3CTaMNe+8AQOzH0tyPjucbmUzotzRQ32k/nkAHVWcKlumUGiwrr7XTC6fwDZg8sM2 sPW1aKp2kdJ2TS+/lvX6PzV06xFotAjYameKNDP04WSsg+p9uTCvhGTGJFEtU06qg+0Q A3IrXDevMsK6Lwf1eRi/rpRZCTjGHujyMHChoNeNOVfhvqB/EauGIiG0wzorJPfPOCcr Vt6WNEL59QDmENiE8iWoSFzEs00J7feZtgApYUIsLGZuqZx/6CFnGNTwDjgODDXT7Kar WNj6LQjCx1u6WkBn45lvg07xaJemf2BOVOCN6jmulOYA/01NNPChGY1urdmB+cl4Z/9w coRw== X-Gm-Message-State: AOAM532cD3ZdaDPyuljmyFxYnQVHNcEii70SH76KjLU2/uykK3PqTjN2 Ofht5qmX0L79d+E1FxMbQvw= X-Google-Smtp-Source: ABdhPJxVOwpFuR9EXZBL5a+hMNupLSf2PEIVaESz1yunHdZuge6PthyITRAnx7rabI0MC5Ut7t5/iw== X-Received: by 2002:a05:6808:10d3:b0:322:90dd:1e20 with SMTP id s19-20020a05680810d300b0032290dd1e20mr6730938ois.30.1651465958060; Sun, 01 May 2022 21:32:38 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id c19-20020a9d7853000000b006060322124csm2522096otm.28.2022.05.01.21.32.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 May 2022 21:32:37 -0700 (PDT) Sender: Guenter Roeck Date: Sun, 1 May 2022 21:32:36 -0700 From: Guenter Roeck To: Michael Walle Cc: Jean Delvare , Rob Herring , Krzysztof Kozlowski , linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/4] lib: add generic polynomial calculation Message-ID: <20220502043236.GA1718668@roeck-us.net> References: <20220401214032.3738095-1-michael@walle.cc> <20220401214032.3738095-2-michael@walle.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220401214032.3738095-2-michael@walle.cc> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > Reviewed-by: Guenter Roeck 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 > + * Serge Semin > + * > + */ > + > +#include > +#include > +#include > + > +/* > + * 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");