From patchwork Fri Apr 13 16:36:47 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Hern=C3=A1n_Gonzalez?= X-Patchwork-Id: 10340475 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 35725604D4 for ; Fri, 13 Apr 2018 16:39:57 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 292C02842A for ; Fri, 13 Apr 2018 16:39:57 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1BDF828646; Fri, 13 Apr 2018 16:39:57 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI, T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B271D2842A for ; Fri, 13 Apr 2018 16:39:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752584AbeDMQiu (ORCPT ); Fri, 13 Apr 2018 12:38:50 -0400 Received: from mail-qk0-f194.google.com ([209.85.220.194]:46737 "EHLO mail-qk0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752774AbeDMQik (ORCPT ); Fri, 13 Apr 2018 12:38:40 -0400 Received: by mail-qk0-f194.google.com with SMTP id l16so8812553qke.13 for ; Fri, 13 Apr 2018 09:38:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vanguardiasur-com-ar.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=BsKK31nhh5Rq1Mce4tGGl6rCkS6mqlLVjHlIlGfPL+4=; b=GQQoAU/m7+NzByXGlDdeXrvdzBmUGM2JERskQURocRmevAVDaNjRtvC/k301OQJkPF w7Fm3RVCmmmxMCo01ExaEELvsxsIwundfu6M/RSD1e4J1Bo7gnEqBXC/9HcIx84D/JPD 2spPORC9vEKjiuI6ECApQcp9LmBqafthodc4IZfhL4FvGdJOF1VF8EYpuniTz7ExBkgk D5mZWLQk0pjHWbzgkb/Wb+6s4Ac1h0GWl/C2hEVX8hzXuwGug/FJV5ox9lbvL7MkkEN4 Zi5dQ6q1iVn806vieO+s0grkDC9wbmNQBCCAwoCdU9a8GvnupIvPk+lo32RdEO2OKe4P Bvrg== 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=BsKK31nhh5Rq1Mce4tGGl6rCkS6mqlLVjHlIlGfPL+4=; b=gD6uYvToY4T0f761Sq8K9/1vlZ0koHsvyX+gr3q8KvC0GpBZvCljvlbVD8kzqz2AdK C4RRszozS3XxujhIZereZiGDefOQA/hKtek2vhWCwSVRxL60rRPBknhyvPuJi7DfQHcn uXGZZzl039MSbiG0BmaLaDGUT+RQl+YmxhKofxTVyjsMjvNjgNLWSyV2BCsR7I/cb4x8 AIxL2Iphah2/I2ROOv0gUyPhaaBEh4vb5KVh9nRxyZ1XwQIcexsKoKNhUJgsUw/vpVSu /xTnoSNEzqtkcQSrX5cItC716qTdcXSQ9kAaRl4TBTTYozpdxLmoRPOpXHGKWjmQXHUw JhqA== X-Gm-Message-State: ALQs6tCdl2j4R1iwbVrZ5CZ0uAFCRZT5u2T9cyxP1hTrmkJIpYEjoXc2 wrmrQFxqnda+gMCyX9ajptleew== X-Google-Smtp-Source: AIpwx48rF7FcRkAGxYNmz90v2jbx5wptjVBSarGOsLLoEpczlBoEVMOgC5OmmifBsiERFJfd/YoOGw== X-Received: by 10.55.139.197 with SMTP id n188mr5101624qkd.212.1523637519911; Fri, 13 Apr 2018 09:38:39 -0700 (PDT) Received: from localhost.localdomain ([190.210.56.45]) by smtp.gmail.com with ESMTPSA id t82sm5024687qke.52.2018.04.13.09.38.37 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 13 Apr 2018 09:38:39 -0700 (PDT) From: =?UTF-8?q?Hern=C3=A1n=20Gonzalez?= To: jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net, gregkh@linuxfoundation.org, Michael.Hennerich@analog.com, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Hern=C3=A1n=20Gonzalez?= Subject: [PATCH v2 10/14] staging: iio: ad7746: Add comments Date: Fri, 13 Apr 2018 13:36:47 -0300 Message-Id: <1523637411-8531-11-git-send-email-hernan@vanguardiasur.com.ar> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1523637411-8531-1-git-send-email-hernan@vanguardiasur.com.ar> References: <1523637411-8531-1-git-send-email-hernan@vanguardiasur.com.ar> MIME-Version: 1.0 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add comments to clarify some of the calculations made, specially when reading or writing values. Signed-off-by: Hernán Gonzalez --- drivers/staging/iio/cdc/ad7746.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c index 05506bf9..ef0ebb5 100644 --- a/drivers/staging/iio/cdc/ad7746.c +++ b/drivers/staging/iio/cdc/ad7746.c @@ -429,6 +429,7 @@ static int ad7746_write_raw(struct iio_dev *indio_dev, goto out; } + /* 2^16 in micro */ val = (val2 * 1024) / 15625; switch (chan->type) { @@ -554,6 +555,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, if (ret < 0) goto out; + /* + * Either for Capacitance, Voltage or Temperature, + * the 0x000000 code represents negative full scale, + * the 0x800000 code represents zero scale, and + * the 0xFFFFFF code represents positive full scale. + */ + *val = (be32_to_cpu(chip->data.d32) & 0xFFFFFF) - 0x800000; switch (chan->type) { @@ -565,7 +573,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, *val = (*val * 125) / 256; break; case IIO_VOLTAGE: - if (chan->channel == 1) /* supply_raw*/ + + /* + * The voltage from the VDD pin is internally + * attenuated by 6. + */ + + if (chan->channel == 1) /* supply_raw */ *val = *val * 6; break; default: @@ -606,6 +620,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, ret = IIO_VAL_INT; break; case IIO_CHAN_INFO_OFFSET: + + /* + * CAPDAC Scale = 21pF_typ / 127 + * CIN Scale = 8.192pF / 2^24 + * Offset Scale = CAPDAC Scale / CIN Scale = 338646 + */ + *val = AD7746_CAPDAC_DACP(chip->capdac[chan->channel] [chan->differential]) * 338646; @@ -614,13 +635,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, case IIO_CHAN_INFO_SCALE: switch (chan->type) { case IIO_CAPACITANCE: - /* 8.192pf / 2^24 */ + /* CIN Scale: 8.192pf / 2^24 */ *val = 0; *val2 = 488; ret = IIO_VAL_INT_PLUS_NANO; break; case IIO_VOLTAGE: - /* 1170mV / 2^23 */ + /* VIN Scale: 1170mV / 2^23 */ *val = 1170; *val2 = 23; ret = IIO_VAL_FRACTIONAL_LOG2; @@ -674,7 +695,8 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) unsigned int tmp; int ret; - /* The default excitation outputs are not inverted, it should be stated + /* + * The default excitation outputs are not inverted, it should be stated * in the dt if needed. */ @@ -685,7 +707,7 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) ret = of_property_read_u32(np, "adi,exclvl", &tmp); if (ret || tmp > 3) { dev_warn(dev, "Wrong exclvl value, using default\n"); - pdata->exclvl = 3; /* default value */ + pdata->exclvl = 3; } else { pdata->exclvl = tmp; }