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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 491E4C433EF for ; Thu, 30 Sep 2021 16:16:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 31895613CD for ; Thu, 30 Sep 2021 16:16:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349558AbhI3QSM (ORCPT ); Thu, 30 Sep 2021 12:18:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:46424 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349301AbhI3QSJ (ORCPT ); Thu, 30 Sep 2021 12:18:09 -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 5D01B613A9; Thu, 30 Sep 2021 16:16:23 +0000 (UTC) Date: Thu, 30 Sep 2021 17:20:18 +0100 From: Jonathan Cameron To: Thomas Gleixner Cc: Iain Hunter , lothar.felten@gmail.com, iain@hunterembedded.co.uk, Lars-Peter Clausen , Alexandru Ardelean , Gwendal Grignou , Matt Ranostay , Arnd Bergmann , Zeng Tao , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] workaround regression in ina2xx introduced by cb47755725da("time: Prevent undefined behaviour in timespec64_to_ns()") Message-ID: <20210930172018.5b4e6660@jic23-huawei> In-Reply-To: <20210930171844.0c67b0ff@jic23-huawei> References: <20210926171711.194901-1-drhunter95@gmail.com> <87o88favd9.ffs@tglx> <20210930171844.0c67b0ff@jic23-huawei> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.30; 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 Thu, 30 Sep 2021 17:18:44 +0100 Jonathan Cameron wrote: > On Sun, 26 Sep 2021 23:18:42 +0200 > Thomas Gleixner wrote: > > > On Sun, Sep 26 2021 at 18:16, Iain Hunter wrote: > > > --- a/drivers/iio/adc/ina2xx-adc.c > > > +++ b/drivers/iio/adc/ina2xx-adc.c > > > @@ -817,10 +817,10 @@ static int ina2xx_capture_thread(void *data) > > > */ > > > do { > > > timespec64_add_ns(&next, 1000 * sampling_us); > > > - delta = timespec64_sub(next, now); > > > - delay_us = div_s64(timespec64_to_ns(&delta), 1000); > > > - } while (delay_us <= 0); > > > + } while (timespec64_compare(&next, &now) < 0); > > > > > > + delta = timespec64_sub(next, now); > > > + delay_us = div_s64(timespec64_to_ns(&delta), 1000); > > > > This whole timespec dance does not make any sense and can be completely > > avoided by using just scalar nanoseconds. Untested patch below. > > > > Thanks, > > > > tglx > > Thanks Thomas. > > Iain could you test this approach? Ah. Just seen v4, so I guess you did. Thanks, J > > Thanks, > > Jonathan > > > --- > > --- a/drivers/iio/adc/ina2xx-adc.c > > +++ b/drivers/iio/adc/ina2xx-adc.c > > @@ -775,7 +775,7 @@ static int ina2xx_capture_thread(void *d > > struct ina2xx_chip_info *chip = iio_priv(indio_dev); > > int sampling_us = SAMPLING_PERIOD(chip); > > int ret; > > - struct timespec64 next, now, delta; > > + ktime_t next, now, delta; > > s64 delay_us; > > > > /* > > @@ -785,7 +785,7 @@ static int ina2xx_capture_thread(void *d > > if (!chip->allow_async_readout) > > sampling_us -= 200; > > > > - ktime_get_ts64(&next); > > + next = ktime_get(); > > > > do { > > while (!chip->allow_async_readout) { > > @@ -798,7 +798,7 @@ static int ina2xx_capture_thread(void *d > > * reset the reference timestamp. > > */ > > if (ret == 0) > > - ktime_get_ts64(&next); > > + next = ktime_get(); > > else > > break; > > } > > @@ -807,7 +807,7 @@ static int ina2xx_capture_thread(void *d > > if (ret < 0) > > return ret; > > > > - ktime_get_ts64(&now); > > + now = ktime_get(); > > > > /* > > * Advance the timestamp for the next poll by one sampling > > @@ -816,11 +816,10 @@ static int ina2xx_capture_thread(void *d > > * multiple times, i.e. samples are dropped. > > */ > > do { > > - timespec64_add_ns(&next, 1000 * sampling_us); > > - delta = timespec64_sub(next, now); > > - delay_us = div_s64(timespec64_to_ns(&delta), 1000); > > - } while (delay_us <= 0); > > + next = ktime_add_us(next, sampling_us); > > + } while (next <= now); > > > > + delay_us = ktime_to_us(ktime_sub(next, now)); > > usleep_range(delay_us, (delay_us * 3) >> 1); > > > > } while (!kthread_should_stop()); > > > > >