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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 F2470C4CECC for ; Sun, 15 Sep 2019 12:53:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C408D214D9 for ; Sun, 15 Sep 2019 12:53:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568552012; bh=j1MhtTL/HDQs+iWSaui+/inPThD5GVkIgBWEhB3l9Wg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=qhkVVuCTv+XDAs9xxgZ0oV6HgyPc7sIiAlO5Acr4A9SDT5XGipoCo61S27zwTG8Lj 6RF7r/mZXvmn3EirwshyrrLIoLRhVO6iUcM6jvw1S1Dk9XZ5qsYlMdaPp2npLvDqbw ANIyvBWKATkrz7yNp03FMR8J327c/pMWX76BJNSM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730312AbfIOMxb (ORCPT ); Sun, 15 Sep 2019 08:53:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:33330 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729570AbfIOMxb (ORCPT ); Sun, 15 Sep 2019 08:53:31 -0400 Received: from archlinux (cpc149474-cmbg20-2-0-cust94.5-4.cable.virginm.net [82.4.196.95]) (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 62ADD21479; Sun, 15 Sep 2019 12:53:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568552010; bh=j1MhtTL/HDQs+iWSaui+/inPThD5GVkIgBWEhB3l9Wg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=TBpEfH0L/yWtWIwpEqIT85T7Ccsoz+Int2biZ3vy4zgc/WPx6z6ZAZJSrYQ5AQ/DM 3KRXyf2v5JlfP5eOcP8ROhfCM2JCHyO6FjPLH3bSBzHy3kXzHydaUfF346DV5EbkX5 i5r/ii3GySRU8Y0d93dYnT8CWy/40ByxyFHUCc4M= Date: Sun, 15 Sep 2019 13:53:26 +0100 From: Jonathan Cameron To: Andreas Klinger Cc: knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] iio: adc: hx711: fix bug in sampling of data Message-ID: <20190915135326.69551618@archlinux> In-Reply-To: <20190909123720.qdew2c4evxd6dpyk@arbad> References: <20190909123720.qdew2c4evxd6dpyk@arbad> X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 9 Sep 2019 14:37:21 +0200 Andreas Klinger wrote: > Fix bug in sampling function hx711_cycle() when interrupt occures while > PD_SCK is high. If PD_SCK is high for at least 60 us power down mode of > the sensor is entered which in turn leads to a wrong measurement. > > Switch off interrupts during a PD_SCK high period and move query of DOUT > to the latest point of time which is at the end of PD_SCK low period. > > This bug exists in the driver since it's initial addition. The more > interrupts on the system the higher is the probability that it happens. > > Fixes: c3b2fdd0ea7e ("iio: adc: hx711: Add IIO driver for AVIA HX711") > > Signed-off-by: Andreas Klinger Applied to the fixes-togreg branch of iio.git and marked for stable. Thanks, Jonathan > --- > drivers/iio/adc/hx711.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c > index 88c7fe15003b..0678964dbd21 100644 > --- a/drivers/iio/adc/hx711.c > +++ b/drivers/iio/adc/hx711.c > @@ -101,13 +101,14 @@ struct hx711_data { > static int hx711_cycle(struct hx711_data *hx711_data) > { > int val; > + unsigned long flags; > > /* > * if preempted for more then 60us while PD_SCK is high: > * hx711 is going in reset > * ==> measuring is false > */ > - preempt_disable(); > + local_irq_save(flags); > gpiod_set_value(hx711_data->gpiod_pd_sck, 1); > > /* > @@ -117,7 +118,6 @@ static int hx711_cycle(struct hx711_data *hx711_data) > */ > ndelay(hx711_data->data_ready_delay_ns); > > - val = gpiod_get_value(hx711_data->gpiod_dout); > /* > * here we are not waiting for 0.2 us as suggested by the datasheet, > * because the oscilloscope showed in a test scenario > @@ -125,7 +125,7 @@ static int hx711_cycle(struct hx711_data *hx711_data) > * and 0.56 us for PD_SCK low on TI Sitara with 800 MHz > */ > gpiod_set_value(hx711_data->gpiod_pd_sck, 0); > - preempt_enable(); > + local_irq_restore(flags); > > /* > * make it a square wave for addressing cases with capacitance on > @@ -133,7 +133,8 @@ static int hx711_cycle(struct hx711_data *hx711_data) > */ > ndelay(hx711_data->data_ready_delay_ns); > > - return val; > + /* sample as late as possible */ > + return gpiod_get_value(hx711_data->gpiod_dout); > } > > static int hx711_read(struct hx711_data *hx711_data)