From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C95B2C282C6 for ; Fri, 25 Jan 2019 18:20:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 99F79218D0 for ; Fri, 25 Jan 2019 18:20:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="JG0t3YBY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729194AbfAYSUf (ORCPT ); Fri, 25 Jan 2019 13:20:35 -0500 Received: from rnd-relay.smtp.broadcom.com ([192.19.229.170]:37488 "EHLO rnd-relay.smtp.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726329AbfAYSUf (ORCPT ); Fri, 25 Jan 2019 13:20:35 -0500 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 7AAA730C0A5; Fri, 25 Jan 2019 10:20:29 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.10.3 rnd-relay.smtp.broadcom.com 7AAA730C0A5 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=broadcom.com; s=dkimrelay; t=1548440429; bh=OnBTKt6woy+u6w5wYAW86X+xtJCsSnClrQJsvmKgaP8=; h=From:To:Cc:Subject:Date:From; b=JG0t3YBYG3o9k1hxzlEnmvlHZ9cIty5MU9hayH0MPDMF+RUg+YINy7TI8NLZGdO6s mwCTMN6G0sFA7HlB56zq0ZJIT+iebipS/BVAfmt8sud1PSCpE2/Iqzegsd0936fieV Gm4WthlueHWrwrKKrgo0exJhkVHTkgPYZwhQr7nQ= 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 6D943AC0730; Fri, 25 Jan 2019 10:20:29 -0800 (PST) Received: by stbirv-lnx-2.igp.broadcom.net (Postfix, from userid 47169) id 5188A2800EA; Fri, 25 Jan 2019 10:20:29 -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 v2] iio: adc: ti-ads7950: inconsistency with spi msg Date: Fri, 25 Jan 2019 10:20:22 -0800 Message-Id: <1548440422-27943-1-git-send-email-justinpopo6@gmail.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Fixes: 902c4b2446d4 ("iio: adc: New driver for TI ADS7950 chips") 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..1255d8b 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].tx_buf = &st->single_tx; st->scan_single_xfer[2].rx_buf = &st->single_rx; st->scan_single_xfer[2].len = 2; -- 2.7.4