From patchwork Wed Feb 4 09:07:30 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans Verkuil X-Patchwork-Id: 5775421 Return-Path: X-Original-To: patchwork-linux-input@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id CEBD79F302 for ; Wed, 4 Feb 2015 09:15:50 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 9F047202AE for ; Wed, 4 Feb 2015 09:15:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2EB5E20295 for ; Wed, 4 Feb 2015 09:15:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932975AbbBDJPr (ORCPT ); Wed, 4 Feb 2015 04:15:47 -0500 Received: from lb3-smtp-cloud6.xs4all.net ([194.109.24.31]:39308 "EHLO lb3-smtp-cloud6.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932397AbbBDJPo (ORCPT ); Wed, 4 Feb 2015 04:15:44 -0500 X-Greylist: delayed 440 seconds by postgrey-1.27 at vger.kernel.org; Wed, 04 Feb 2015 04:15:43 EST Received: from tschai.lan ([80.203.20.209]) by smtp-cloud6.xs4all.net with ESMTP id o98J1p00T4Wfp8Y0198MLn; Wed, 04 Feb 2015 10:08:23 +0100 Received: from tschai.fritz.box (localhost [127.0.0.1]) by tschai.lan (Postfix) with ESMTPSA id 339272A14B7; Wed, 4 Feb 2015 10:07:34 +0100 (CET) From: Hans Verkuil To: linux-media@vger.kernel.org Cc: Hans de Goede , Dmitry Torokhov , linux-input@vger.kernel.org, Mauro Carvalho Chehab , Prashant Laddha , Hans Verkuil Subject: [PATCH 1/3] fixp-arith: replace sin/cos table by a better precision one Date: Wed, 4 Feb 2015 10:07:30 +0100 Message-Id: <1423040852-7470-2-git-send-email-hverkuil@xs4all.nl> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1423040852-7470-1-git-send-email-hverkuil@xs4all.nl> References: <1423040852-7470-1-git-send-email-hverkuil@xs4all.nl> Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Mauro Carvalho Chehab The cos table used at fixp-arith.h has only 8 bits of precision. That causes problems if it is reused on other drivers. As some media drivers require a higher precision sin/cos implementation, replace the current implementation by one that will provide 32 bits precision. The values generated by the new implementation matches the 32 bit precision of glibc's sin for an angle measured in integer degrees. It also provides support for fractional angles via linear interpolation. On experimental calculus, when used a table with a 0.001 degree angle, the maximum error for sin is 0.000038, which is likely good enough for practical purposes. There are some logic there that seems to be specific to the usage inside ff-memless.c. Move those logic to there, as they're not needed elsewhere. Cc: Hans de Goede Cc: Dmitry Torokhov Cc: linux-input@vger.kernel.org Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Prashant Laddha Signed-off-by: Hans Verkuil Acked-by: Dmitry Torokhov --- drivers/input/ff-memless.c | 18 ++++- drivers/media/usb/gspca/ov534.c | 11 +-- include/linux/fixp-arith.h | 145 +++++++++++++++++++++++++++++----------- 3 files changed, 125 insertions(+), 49 deletions(-) diff --git a/drivers/input/ff-memless.c b/drivers/input/ff-memless.c index 74c0d8c..fcc6c33 100644 --- a/drivers/input/ff-memless.c +++ b/drivers/input/ff-memless.c @@ -237,6 +237,18 @@ static u16 ml_calculate_direction(u16 direction, u16 force, (force + new_force)) << 1; } +#define FRAC_N 8 +static inline s16 fixp_new16(s16 a) +{ + return ((s32)a) >> (16 - FRAC_N); +} + +static inline s16 fixp_mult(s16 a, s16 b) +{ + a = ((s32)a * 0x100) / 0x7fff; + return ((s32)(a * b)) >> FRAC_N; +} + /* * Combine two effects and apply gain. */ @@ -247,7 +259,7 @@ static void ml_combine_effects(struct ff_effect *effect, struct ff_effect *new = state->effect; unsigned int strong, weak, i; int x, y; - fixp_t level; + s16 level; switch (new->type) { case FF_CONSTANT: @@ -255,8 +267,8 @@ static void ml_combine_effects(struct ff_effect *effect, level = fixp_new16(apply_envelope(state, new->u.constant.level, &new->u.constant.envelope)); - x = fixp_mult(fixp_sin(i), level) * gain / 0xffff; - y = fixp_mult(-fixp_cos(i), level) * gain / 0xffff; + x = fixp_mult(fixp_sin16(i), level) * gain / 0xffff; + y = fixp_mult(-fixp_cos16(i), level) * gain / 0xffff; /* * here we abuse ff_ramp to hold x and y of constant force * If in future any driver wants something else than x and y diff --git a/drivers/media/usb/gspca/ov534.c b/drivers/media/usb/gspca/ov534.c index a9c866d..146071b 100644 --- a/drivers/media/usb/gspca/ov534.c +++ b/drivers/media/usb/gspca/ov534.c @@ -816,21 +816,16 @@ static void sethue(struct gspca_dev *gspca_dev, s32 val) s16 huesin; s16 huecos; - /* fixp_sin and fixp_cos accept only positive values, while - * our val is between -90 and 90 - */ - val += 360; - /* According to the datasheet the registers expect HUESIN and * HUECOS to be the result of the trigonometric functions, * scaled by 0x80. * - * The 0x100 here represents the maximun absolute value + * The 0x7fff here represents the maximum absolute value * returned byt fixp_sin and fixp_cos, so the scaling will * consider the result like in the interval [-1.0, 1.0]. */ - huesin = fixp_sin(val) * 0x80 / 0x100; - huecos = fixp_cos(val) * 0x80 / 0x100; + huesin = fixp_sin16(val) * 0x80 / 0x7fff; + huecos = fixp_cos16(val) * 0x80 / 0x7fff; if (huesin < 0) { sccb_reg_write(gspca_dev, 0xab, diff --git a/include/linux/fixp-arith.h b/include/linux/fixp-arith.h index 3089d73..d4686fe 100644 --- a/include/linux/fixp-arith.h +++ b/include/linux/fixp-arith.h @@ -1,6 +1,8 @@ #ifndef _FIXP_ARITH_H #define _FIXP_ARITH_H +#include + /* * Simplistic fixed-point arithmetics. * Hmm, I'm probably duplicating some code :( @@ -29,59 +31,126 @@ #include -/* The type representing fixed-point values */ -typedef s16 fixp_t; +static const s32 sin_table[] = { + 0x00000000, 0x023be165, 0x04779632, 0x06b2f1d2, 0x08edc7b6, 0x0b27eb5c, + 0x0d61304d, 0x0f996a26, 0x11d06c96, 0x14060b67, 0x163a1a7d, 0x186c6ddd, + 0x1a9cd9ac, 0x1ccb3236, 0x1ef74bf2, 0x2120fb82, 0x234815ba, 0x256c6f9e, + 0x278dde6e, 0x29ac379f, 0x2bc750e8, 0x2ddf003f, 0x2ff31bdd, 0x32037a44, + 0x340ff241, 0x36185aee, 0x381c8bb5, 0x3a1c5c56, 0x3c17a4e7, 0x3e0e3ddb, + 0x3fffffff, 0x41ecc483, 0x43d464fa, 0x45b6bb5d, 0x4793a20f, 0x496af3e1, + 0x4b3c8c11, 0x4d084650, 0x4ecdfec6, 0x508d9210, 0x5246dd48, 0x53f9be04, + 0x55a6125a, 0x574bb8e5, 0x58ea90c2, 0x5a827999, 0x5c135399, 0x5d9cff82, + 0x5f1f5ea0, 0x609a52d1, 0x620dbe8a, 0x637984d3, 0x64dd894f, 0x6639b039, + 0x678dde6d, 0x68d9f963, 0x6a1de735, 0x6b598ea1, 0x6c8cd70a, 0x6db7a879, + 0x6ed9eba0, 0x6ff389de, 0x71046d3c, 0x720c8074, 0x730baeec, 0x7401e4bf, + 0x74ef0ebb, 0x75d31a5f, 0x76adf5e5, 0x777f903b, 0x7847d908, 0x7906c0af, + 0x79bc384c, 0x7a6831b8, 0x7b0a9f8c, 0x7ba3751c, 0x7c32a67c, 0x7cb82884, + 0x7d33f0c8, 0x7da5f5a3, 0x7e0e2e31, 0x7e6c924f, 0x7ec11aa3, 0x7f0bc095, + 0x7f4c7e52, 0x7f834ecf, 0x7fb02dc4, 0x7fd317b3, 0x7fec09e1, 0x7ffb025e, + 0x7fffffff +}; -#define FRAC_N 8 -#define FRAC_MASK ((1< 180) { + negative = true; + degrees -= 180; + } + if (degrees > 90) + degrees = 180 - degrees; + ret = sin_table[degrees]; -/* a: 123 -> 123.0 */ -static inline fixp_t fixp_new(s16 a) -{ - return a< -1.0 - 0x8000 -> 1.0 - 0x0000 -> 0.0 -*/ -static inline fixp_t fixp_new16(s16 a) +/** + * fixp_sin32() returns the sin of an angle in degrees + * + * @degrees: angle, in degrees. The angle can be positive or negative + * + * The returned value ranges from -0x7fffffff to +0x7fffffff. + */ +static inline s32 fixp_sin32(int degrees) { - return ((s32)a)>>(16-FRAC_N); + degrees = (degrees % 360 + 360) % 360; + + return __fixp_sin32(degrees); } -static inline fixp_t fixp_cos(unsigned int degrees) +/* cos(x) = sin(x + 90 degrees) */ +#define fixp_cos32(v) fixp_sin32((v) + 90) + +/* + * 16 bits variants + * + * The returned value ranges from -0x7fff to 0x7fff + */ + +#define fixp_sin16(v) (fixp_sin32(v) >> 16) +#define fixp_cos16(v) (fixp_cos32(v) >> 16) + +/** + * fixp_sin32_rad() - calculates the sin of an angle in radians + * + * @radians: angle, in radians + * @twopi: value to be used for 2*pi + * + * Provides a variant for the cases where just 360 + * values is not enough. This function uses linear + * interpolation to a wider range of values given by + * twopi var. + * + * Experimental tests gave a maximum difference of + * 0.000038 between the value calculated by sin() and + * the one produced by this function, when twopi is + * equal to 360000. That seems to be enough precision + * for practical purposes. + * + * Please notice that two high numbers for twopi could cause + * overflows, so the routine will not allow values of twopi + * bigger than 1^18. + */ +static inline s32 fixp_sin32_rad(u32 radians, u32 twopi) { - int quadrant = (degrees / 90) & 3; - unsigned int i = degrees % 90; + int degrees; + s32 v1, v2, dx, dy; + s64 tmp; - if (quadrant == 1 || quadrant == 3) - i = 90 - i; + /* + * Avoid too large values for twopi, as we don't want overflows. + */ + BUG_ON(twopi > 1 << 18); - i >>= 1; + degrees = (radians * 360) / twopi; + tmp = radians - (degrees * twopi) / 360; - return (quadrant == 1 || quadrant == 2)? -cos_table[i] : cos_table[i]; -} + degrees = (degrees % 360 + 360) % 360; + v1 = __fixp_sin32(degrees); -static inline fixp_t fixp_sin(unsigned int degrees) -{ - return -fixp_cos(degrees + 90); -} + v2 = fixp_sin32(degrees + 1); -static inline fixp_t fixp_mult(fixp_t a, fixp_t b) -{ - return ((s32)(a*b))>>FRAC_N; + dx = twopi / 360; + dy = v2 - v1; + + tmp *= dy; + + return v1 + div_s64(tmp, dx); } +/* cos(x) = sin(x + pi/2 radians) */ + +#define fixp_cos32_rad(rad, twopi) \ + fixp_sin32_rad(rad + twopi / 4, twopi) + #endif