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=-15.5 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 AB956C47082 for ; Thu, 3 Jun 2021 16:18:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9278D613E4 for ; Thu, 3 Jun 2021 16:18:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229845AbhFCQUa (ORCPT ); Thu, 3 Jun 2021 12:20:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:59890 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229506AbhFCQU3 (ORCPT ); Thu, 3 Jun 2021 12:20:29 -0400 Received: from jic23-huawei (cpc108967-cmbg20-2-0-cust86.5-4.cable.virginm.net [81.101.6.87]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 44611613D2; Thu, 3 Jun 2021 16:18:41 +0000 (UTC) Date: Thu, 3 Jun 2021 17:20:25 +0100 From: Jonathan Cameron To: Meng.Li@windriver.com Cc: lars@metafoo.de, Michael.Hennerich@analog.com, pmeerw@pmeerw.net, u.kleine-koenig@pengutronix.de, linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org Subject: Re: [PATCH] driver: adc: ltc2497: return directly after reading the adc conversion value Message-ID: <20210603172025.314b5ced@jic23-huawei> In-Reply-To: <20210601092805.18385-1-Meng.Li@windriver.com> References: <20210601092805.18385-1-Meng.Li@windriver.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 1 Jun 2021 17:28:05 +0800 Meng.Li@windriver.com wrote: > From: Meng Li > > When read adc conversion value with below command: > cat /sys/.../iio:device0/in_voltage0-voltage1_raw > There is an error reported as below: > ltc2497 0-0014: i2c transfer failed: -EREMOTEIO > This i2c transfer issue is introduced by commit 69548b7c2c4f ("iio: > adc: ltc2497: split protocol independent part in a separate module"). > When extract the common code into ltc2497-core.c, it change the > code logic of function ltc2497core_read(). With wrong reading > sequence, the action of enable adc channel is sent to chip again > during adc channel is in conversion status. In this way, there is > no ack from chip, and then cause i2c transfer failed. > In order to keep the code logic is the same with original ideal, > it is need to return direct after reading the adc conversion value. > > v2: > According to ltc2497 datasheet, the max value of conversion time is > 149.9 ms. So, add 20% to the 150msecs so that there is enough time > for data conversion. Version change logs go below the --- as we don't want to preserve them forever in the git history. I may have lost track of the discussion, but I thought the idea was that perhaps the longer time period would remove the need for the early return? Thanks, Jonathan > > Fixes: 69548b7c2c4f ("iio: adc: ltc2497: split protocol independent part in a separate module ") > Cc: stable@vger.kernel.org > Signed-off-by: Meng Li > --- > drivers/iio/adc/ltc2497.c | 2 ++ > drivers/iio/adc/ltc2497.h | 2 +- > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c > index 1adddf5a88a9..fd5a66860a47 100644 > --- a/drivers/iio/adc/ltc2497.c > +++ b/drivers/iio/adc/ltc2497.c > @@ -41,6 +41,8 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata, > } > > *val = (be32_to_cpu(st->buf) >> 14) - (1 << 17); > + > + return ret; > } > > ret = i2c_smbus_write_byte(st->client, > diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h > index d0b42dd6b8ad..e451930837d8 100644 > --- a/drivers/iio/adc/ltc2497.h > +++ b/drivers/iio/adc/ltc2497.h > @@ -2,7 +2,7 @@ > > #define LTC2497_ENABLE 0xA0 > #define LTC2497_CONFIG_DEFAULT LTC2497_ENABLE > -#define LTC2497_CONVERSION_TIME_MS 150ULL > +#define LTC2497_CONVERSION_TIME_MS 180ULL > > struct ltc2497core_driverdata { > struct regulator *ref;