From patchwork Mon Apr 20 20:40:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Linus Walleij X-Patchwork-Id: 11499823 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E803F913 for ; Mon, 20 Apr 2020 20:40:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CFE0420857 for ; Mon, 20 Apr 2020 20:40:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="lL8jv7BB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726207AbgDTUkc (ORCPT ); Mon, 20 Apr 2020 16:40:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725774AbgDTUkb (ORCPT ); Mon, 20 Apr 2020 16:40:31 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90811C061A0C for ; Mon, 20 Apr 2020 13:40:31 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id e25so11597190ljg.5 for ; Mon, 20 Apr 2020 13:40:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=1+vHbHPDXWO2KyltN0oHVXvvCaxZJYvjk+daKL1jRQg=; b=lL8jv7BBJcgAWWxjqfmxHRuLc+LEc6KifjaVt0NvzrW9XZ67F7gG6qO2AjNiXbdFpu i5R3j01rDHt3z/mceb/zxyE+RTNmpew/NZi2IjxAOHV0JbfC36r2aMFXWEEJWkciZqGV 6evOJSpnQQTkJu3hq1hVYu2dqI67VFEkXMafccqLz8uOrTiJZFpek6kT9N3seaV3BiEB 1+WbQVJabXkGx2E3Fr+O0M3r/Joy40EdyD69kvmS673ENldpiVXJtc8TS1E6+Bo9qP87 cWbxyLGtrirnQNvBTp5v5A0OgvzMOR+yiLyDwIG+KBy07PAeDdmc5RNCrl2sR3QynQpc fzMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=1+vHbHPDXWO2KyltN0oHVXvvCaxZJYvjk+daKL1jRQg=; b=PItOx+6TdBf60Ru29x5SzRUc8mzj5rB5bE7iYukK+ufHldy6lbzHbQMun+whAvS71Y 1aomRc0/UTAttOgnvMP/p1eTeWkXzliqKtfTkBiANIFGXhbqNLAQxEMtN2aKo1fTbnBO MoI509FWjp5n4Z8hqIoW3DM34Q3t7ke3BRlM/il1B83sljWhIeAmbDrY5GHhC08Dg3zV BTUK6YqKaM71JNjBHIVTZQtVyISTjuVzlvMWruJYLkEmNjC7h505xljvH53x0JfzyW31 WBI93sFDAnZIcwCT5LKkjlLOxtP8FZNicyJie0vVr05e+iTywkvOqNx62FzRQKF6Nhru 8+xg== X-Gm-Message-State: AGi0PubIgBHLBi7p11uoFOxr2uO4ec6dDNaFG8BwiJ+O2HrtTdhP99Gh W12jhRvpkKn/jir0nd2RkmMkmQ== X-Google-Smtp-Source: APiQypI9l0uGHPWRg+ZpH8uWLlpt6agKj6OmqGdfFjnStlaksoKJ229ep147HVuklcXe+j8SZfp1xw== X-Received: by 2002:a2e:b0ca:: with SMTP id g10mr11485118ljl.169.1587415229894; Mon, 20 Apr 2020 13:40:29 -0700 (PDT) Received: from localhost.bredbandsbolaget (c-f3d7225c.014-348-6c756e10.bbcust.telenor.se. [92.34.215.243]) by smtp.gmail.com with ESMTPSA id y22sm336637lfg.92.2020.04.20.13.40.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Apr 2020 13:40:29 -0700 (PDT) From: Linus Walleij To: Jonathan Cameron , linux-iio@vger.kernel.org Cc: Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , linux-input@vger.kernel.org, Linus Walleij , Nick Reitemeyer , Stephan Gerhold , =?utf-8?b?TWljaGHFgiBNaXJvc8WCYXc=?= Subject: [PATCH 3/3 v4] iio: magnetometer: ak8974: Provide scaling Date: Mon, 20 Apr 2020 22:40:22 +0200 Message-Id: <20200420204022.18235-3-linus.walleij@linaro.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200420204022.18235-1-linus.walleij@linaro.org> References: <20200420204022.18235-1-linus.walleij@linaro.org> MIME-Version: 1.0 Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org The manual for the HSCDTD008A gives us a scaling for the three axis as +/- 2.4mT (24 Gauss) per axis. The manual for the AMI305 and AMI306 gives us a scaling for the three axis as +/- 12 Gauss per axis. Tests with the HSCDTD008A sensor, cat the raw values: $ cat in_magn_*_raw raw 45 189 -19 The scaling factor in in_magn_*_scale is 0.001464843, which gives: 0.065 Gauss 0.277 Gauss -0.027 Gauss The earths magnetic field is in the range of 0.25 to 0.65 Gauss on the surface according to Wikipedia, so these seem like reasonable values. Again we are guessing that the AK8974 has a 12 bit ADC, based on the similarity with AMI305 and AMI306. Cc: Nick Reitemeyer Cc: Stephan Gerhold Cc: Michał Mirosław Signed-off-by: Linus Walleij --- ChangeLog v3->v4: - Do not multiply the range with 2, instead divide by two in divisor and dividend. (Thus it becomes 2^11 and 2^14 respectively.) - Use the IIO_VAL_FRACTIONAL_LOG2 trick and pass 2^11 or 2^14 as range. ChangeLog v2->v3: - Scale the 2.4mT/24Gauss to 15 bits for the HSCDTD008A. - Scale the 12 Gauss to 12 bits for the AMI305/AMI306 - Use 12 bits for the other variants. - Return directly in the raw read function. ChangeLog v1->v2: - Split out the measurement refactoring. --- drivers/iio/magnetometer/ak8974.c | 45 ++++++++++++++++++++++++++++++- 1 file changed, 44 insertions(+), 1 deletion(-) diff --git a/drivers/iio/magnetometer/ak8974.c b/drivers/iio/magnetometer/ak8974.c index fb6d84b79a7a..2d500be9da40 100644 --- a/drivers/iio/magnetometer/ak8974.c +++ b/drivers/iio/magnetometer/ak8974.c @@ -606,6 +606,48 @@ static int ak8974_read_raw(struct iio_dev *indio_dev, if (ret) return ret; return IIO_VAL_INT; + case IIO_CHAN_INFO_SCALE: + switch (ak8974->variant) { + case AK8974_WHOAMI_VALUE_AMI306: + case AK8974_WHOAMI_VALUE_AMI305: + /* + * The datasheet for AMI305 and AMI306, page 6 + * specifies the range of the sensor to be + * +/- 12 Gauss. + */ + *val = 12; + /* + * 12 bits are used, +/- 2^11 + * [ -2048 .. 2047 ] (manual page 20) + * [ 0xf800 .. 0x07ff ] + */ + *val2 = 11; + return IIO_VAL_FRACTIONAL_LOG2; + case AK8974_WHOAMI_VALUE_HSCDTD008A: + /* + * The datasheet for HSCDTF008A, page 3 specifies the + * range of the sensor as +/- 2.4 mT per axis, which + * corresponds to +/- 2400 uT = +/- 24 Gauss. + */ + *val = 24; + /* + * 15 bits are used (set up in CTRL4), +/- 2^14 + * [ -16384 .. 16383 ] (manual page 24) + * [ 0xc000 .. 0x3fff ] + */ + *val2 = 14; + return IIO_VAL_FRACTIONAL_LOG2; + default: + /* GUESSING +/- 12 Gauss */ + *val = 12; + /* GUESSING 12 bits ADC +/- 2^11 */ + *val2 = 11; + return IIO_VAL_FRACTIONAL_LOG2; + } + break; + default: + /* Unknown request */ + break; } return -EINVAL; @@ -670,7 +712,8 @@ static const struct iio_chan_spec_ext_info ak8974_ext_info[] = { .type = IIO_MAGN, \ .modified = 1, \ .channel2 = IIO_MOD_##axis, \ - .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \ + BIT(IIO_CHAN_INFO_SCALE), \ .ext_info = ak8974_ext_info, \ .address = index, \ .scan_index = index, \