From patchwork Fri Jan 25 01:56:54 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Justin Chen X-Patchwork-Id: 10780357 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 C6E8A1399 for ; Fri, 25 Jan 2019 02:05:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B2C122FABE for ; Fri, 25 Jan 2019 02:05:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A6EF22FAC1; Fri, 25 Jan 2019 02:05:36 +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,DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FROM,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 46C212FABE for ; Fri, 25 Jan 2019 02:05:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728362AbfAYCFf (ORCPT ); Thu, 24 Jan 2019 21:05:35 -0500 Received: from rnd-relay.smtp.broadcom.com ([192.19.229.170]:36094 "EHLO rnd-relay.smtp.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727983AbfAYCFf (ORCPT ); Thu, 24 Jan 2019 21:05:35 -0500 X-Greylist: delayed 502 seconds by postgrey-1.27 at vger.kernel.org; Thu, 24 Jan 2019 21:05:35 EST Received: from nis-sj1-27.broadcom.com (nis-sj1-27.lvn.broadcom.net [10.75.144.136]) by rnd-relay.smtp.broadcom.com (Postfix) with ESMTP id E1AAC30C012; Thu, 24 Jan 2019 17:57:11 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.10.3 rnd-relay.smtp.broadcom.com E1AAC30C012 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=broadcom.com; s=dkimrelay; t=1548381431; bh=cZOP/nX3nnggIGwSwr68BY+QBEhuNcDNNNnqUyDj8rk=; h=From:To:Cc:Subject:Date:From; b=gx9mFuZ3mwaDlKdhz9+KpZ8SL8CA5iHUJdvyFcGDOazTGM/71Uvn9cB9V5uMO+o7+ jIfOwhvgJKp6nMwn5GRVkKk/SUF++5ykFUF5mDtUaBu15LZOoZ3WhhyT4li5ARhZm7 fRSsTTsTJe2WzxW2/yWYyUjzZNELMo4jyy5O9Kjg= Received: from stbirv-lnx-2.igp.broadcom.net (stbirv-lnx-2.igp.broadcom.net [10.67.48.34]) by nis-sj1-27.broadcom.com (Postfix) with ESMTP id 3690DAC074C; Thu, 24 Jan 2019 17:57:12 -0800 (PST) Received: by stbirv-lnx-2.igp.broadcom.net (Postfix, from userid 47169) id 15E2A2800EA; Thu, 24 Jan 2019 17:57:12 -0800 (PST) From: justinpopo6@gmail.com To: linux-iio@vger.kernel.org Cc: jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de, linux-kernel@vger.kernel.org, f.fainelli@gmail.com, Justin Chen Subject: [PATCH] iio: adc: ti-ads7950: inconsistency with spi msg Date: Thu, 24 Jan 2019 17:56:54 -0800 Message-Id: <1548381414-20561-1-git-send-email-justinpopo6@gmail.com> X-Mailer: git-send-email 2.7.4 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 From: Justin Chen To read a channel we require 3 cycles to send, process, and receive the data. The transfer buffer for the third transaction is left blank. This leaves it up to the SPI driver to decide what to do. In one particular case, if the tx buffer is not set the spi driver sets it to 0xff. This puts the ADC in a alarm programming state, therefore the following read to a channel becomes erroneous. Instead of leaving us to the mercy of the SPI driver, we send the ADC cmd on the third transaction to prevent inconsistent behavior. Signed-off-by: Justin Chen --- drivers/iio/adc/ti-ads7950.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c index 0ad6359..5453e10 100644 --- a/drivers/iio/adc/ti-ads7950.c +++ b/drivers/iio/adc/ti-ads7950.c @@ -422,6 +422,7 @@ static int ti_ads7950_probe(struct spi_device *spi) st->scan_single_xfer[1].tx_buf = &st->single_tx; st->scan_single_xfer[1].len = 2; st->scan_single_xfer[1].cs_change = 1; + st->scan_single_xfer[2].rx_buf = &st->single_tx; st->scan_single_xfer[2].rx_buf = &st->single_rx; st->scan_single_xfer[2].len = 2;