From patchwork Fri Jul 9 10:11:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= X-Patchwork-Id: 12367077 X-Patchwork-Delegate: jic23@cam.ac.uk 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=-17.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 530B7C07E99 for ; Fri, 9 Jul 2021 10:11:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2F008613D1 for ; Fri, 9 Jul 2021 10:11:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232006AbhGIKOK (ORCPT ); Fri, 9 Jul 2021 06:14:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231864AbhGIKOJ (ORCPT ); Fri, 9 Jul 2021 06:14:09 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7AC18C0613DD for ; Fri, 9 Jul 2021 03:11:25 -0700 (PDT) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1m1nTb-0003gV-8y; Fri, 09 Jul 2021 12:11:19 +0200 Received: from [2a0a:edc0:0:900:1d::77] (helo=ptz.office.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1m1nTa-0003oR-1U; Fri, 09 Jul 2021 12:11:18 +0200 Received: from ukl by ptz.office.stw.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1m1nTa-0001MI-07; Fri, 09 Jul 2021 12:11:18 +0200 From: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= To: Jonathan Cameron Cc: Lars-Peter Clausen , David Lechner , linux-iio@vger.kernel.org, kernel@pengutronix.de Subject: [PATCH] iio: adc: ti-ads7950: Ensure CS is deasserted after reading channels Date: Fri, 9 Jul 2021 12:11:10 +0200 Message-Id: <20210709101110.1814294-1-u.kleine-koenig@pengutronix.de> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-iio@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org The ADS7950 requires that CS is deasserted after each SPI word. Before commit e2540da86ef8 ("iio: adc: ti-ads7950: use SPI_CS_WORD to reduce CPU usage") the driver used a message with one spi transfer per channel where each but the last one had .cs_change set to enforce a CS toggle. This was wrongly translated into a message with a single transfer and .cs_change set which results in a CS toggle after each word but the last which corrupts the first adc conversion of all readouts after the first readout. Fixes: e2540da86ef8 ("iio: adc: ti-ads7950: use SPI_CS_WORD to reduce CPU usage") Signed-off-by: Uwe Kleine-König Reviewed-by: David Lechner Tested-by: David Lechner --- drivers/iio/adc/ti-ads7950.c | 1 - 1 file changed, 1 deletion(-) diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c index 2383eacada87..a2b83f0bd526 100644 --- a/drivers/iio/adc/ti-ads7950.c +++ b/drivers/iio/adc/ti-ads7950.c @@ -568,7 +568,6 @@ static int ti_ads7950_probe(struct spi_device *spi) st->ring_xfer.tx_buf = &st->tx_buf[0]; st->ring_xfer.rx_buf = &st->rx_buf[0]; /* len will be set later */ - st->ring_xfer.cs_change = true; spi_message_add_tail(&st->ring_xfer, &st->ring_msg);