From patchwork Fri Apr 1 21:40:29 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Walle X-Patchwork-Id: 555674 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 62E1EC43217 for ; Fri, 1 Apr 2022 21:40:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352855AbiDAVme (ORCPT ); Fri, 1 Apr 2022 17:42:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350341AbiDAVmd (ORCPT ); Fri, 1 Apr 2022 17:42:33 -0400 Received: from ssl.serverraum.org (ssl.serverraum.org [176.9.125.105]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE01D265E80; Fri, 1 Apr 2022 14:40:42 -0700 (PDT) Received: from mwalle01.kontron.local. (unknown [213.135.10.150]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 9FFB022246; Fri, 1 Apr 2022 23:40:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1648849239; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XNfzlXOyFywZQcwSKiDkoJ3VdJIckZGycW6wccqMDNM=; b=l2gBFqdLQOJXTM+fntCCP++Inkkw1Y1O13+uTgz8+O4zfTEQzUpwnjH2cAfcdFKAf5pLL1 m2eQNK0EeKWEioJwFIkuL5a1VFftYBC1ZtxBeoyd+dUjZcdzNetwaIbscY4L9xedVMGBFW HLxXQZW0kpu2T1gb2bLkmgu0xnnRL9Q= From: Michael Walle To: Jean Delvare , Guenter Roeck , Rob Herring , Krzysztof Kozlowski Cc: linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Walle Subject: [PATCH v4 1/4] lib: add generic polynomial calculation Date: Fri, 1 Apr 2022 23:40:29 +0200 Message-Id: <20220401214032.3738095-2-michael@walle.cc> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220401214032.3738095-1-michael@walle.cc> References: <20220401214032.3738095-1-michael@walle.cc> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 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 --- 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");