From patchwork Thu May 2 16:14:32 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adam Michaelis X-Patchwork-Id: 10927303 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E45D81395 for ; Thu, 2 May 2019 16:14:48 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D660C20587 for ; Thu, 2 May 2019 16:14:48 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CAA04205F7; Thu, 2 May 2019 16:14:48 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham 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 EE49D20587 for ; Thu, 2 May 2019 16:14:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726303AbfEBQOq (ORCPT ); Thu, 2 May 2019 12:14:46 -0400 Received: from secvs02.rockwellcollins.com ([205.175.225.241]:35722 "EHLO secvs02.rockwellcollins.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726524AbfEBQOp (ORCPT ); Thu, 2 May 2019 12:14:45 -0400 Received: from ofwgwc03.rockwellcollins.com (HELO ciulimr02.rockwellcollins.com) ([205.175.225.12]) by secvs02.rockwellcollins.com with ESMTP; 02 May 2019 11:14:44 -0500 X-Received: from righttwix.rockwellcollins.com (righttwix.rockwellcollins.com [192.168.141.218]) by ciulimr02.rockwellcollins.com (Postfix) with ESMTP id DAF692007E; Thu, 2 May 2019 11:14:43 -0500 (CDT) From: Adam Michaelis To: linux-iio@vger.kernel.org Cc: lars@metafoo.de, michael.hennerich@analog.com, jic23@kernel.org, knaack.h@gmx.de, pmeerw@pmeerw.net, robh+dt@kernel.org, mark.rutland@arm.com, charles-antoine.couret@essensium.com, devicetree@vger.kernel.org, brandon.maier@rockwellcollins.com, clayton.shotwell@rockwellcollins.com, Adam Michaelis Subject: [PATCH v2 6/6] iio: ad7949: Fix dummy read cycle placement Date: Thu, 2 May 2019 11:14:32 -0500 Message-Id: <1556813672-49861-6-git-send-email-adam.michaelis@rockwellcollins.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1556813672-49861-1-git-send-email-adam.michaelis@rockwellcollins.com> References: <1556813672-49861-1-git-send-email-adam.michaelis@rockwellcollins.com> 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 The AD7949 requires two conversion cycles following any configuration change (including changing the analog channel being sampled). Therefore, adding a dummy read cycle when config is changed and removing the extra cycles at initial configuration. Signed-off-by: Adam Michaelis --- V2: Add some defines to reduce use of magic numbers. --- drivers/iio/adc/ad7949.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c index cba152151908..5a6fe522c931 100644 --- a/drivers/iio/adc/ad7949.c +++ b/drivers/iio/adc/ad7949.c @@ -144,6 +144,25 @@ static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val, * time to send a new command to the device */ udelay(2); + + /* + * Perform extra read cycle to allow configuration, acquisition, + * and conversion sequences to complete for new configuration. + */ + (void)memset(&tx, 0, sizeof(tx)); + (void)memset(ad7949_adc->buffer, 0, AD7949_BUFFER_LEN); + + tx.rx_buf = ad7949_adc->buffer; + tx.len = ad7949_message_len(ad7949_adc); + + spi_message_init_with_transfers(&msg, &tx, 1); + ret = spi_sync(ad7949_adc->spi, &msg); + + /* + * This delay is to avoid a new request before the required time + * to send a new command to the device. + */ + udelay(2); } return ret; @@ -276,7 +295,6 @@ static int ad7949_spi_reg_access(struct iio_dev *indio_dev, static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc) { int ret; - int val; u16 adc_config = 0; ad7949_adc->current_channel = 0; @@ -309,13 +327,6 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc) adc_config, AD7949_CFG_MASK_TOTAL); - /* - * Do two dummy conversions to apply the first configuration setting. - * Required only after the start up of the device. - */ - ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel); - ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel); - return ret; }