From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751756AbdLBLtz (ORCPT ); Sat, 2 Dec 2017 06:49:55 -0500 Received: from mail.kernel.org ([198.145.29.99]:55344 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751628AbdLBLty (ORCPT ); Sat, 2 Dec 2017 06:49:54 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 04F0321905 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jic23@kernel.org Date: Sat, 2 Dec 2017 11:49:49 +0000 From: Jonathan Cameron To: Arnd Bergmann Cc: y2038@lists.linaro.org, Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Subject: Re: [PATCH] iio: common: ssp_sensors: use ktime_get_real_ns() timestamps Message-ID: <20171202114949.2d9bf320@archlinux> In-Reply-To: <20171127115158.2884398-1-arnd@arndb.de> References: <20171127115158.2884398-1-arnd@arndb.de> X-Mailer: Claws Mail 3.15.1-dirty (GTK+ 2.24.31; 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 27 Nov 2017 12:51:48 +0100 Arnd Bergmann wrote: > getnstimeofday() suffers from the overflow in y2038 on 32-bit > architectures and requires a conversion into the nanosecond format that > we want here. > > This changes ssp_parse_dataframe() to use ktime_get_real_ns() directly, > which does not have that problem. > > An open question is what time base should be used here. Normally > timestamps should use ktime_get_ns() or ktime_get_boot_ns() to read > monotonic time instead of "real" time, which suffers from time jumps > due to settimeofday() calls or leap seconds. > > Signed-off-by: Arnd Bergmann +cc Karol Wrona. Fix looks fine to me, but might be nice to address that and the question of using a monotonic clock all in one go. This is probably a copy of an ancient piece of my stupidity where I used the wrong clock for the core IIO timestamping code. We fixed that a while back by letting the user chose the clock. If you are running slow enough you actually do want the 'real' time - probably never the case here though. If we don't hear from Karol for a few weeks I'll pick this up and we can address the wrong timestamp sometime in the future! Jonathan > --- > drivers/iio/common/ssp_sensors/ssp_spi.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/drivers/iio/common/ssp_sensors/ssp_spi.c b/drivers/iio/common/ssp_sensors/ssp_spi.c > index 704284a475ae..2ab106bb3e03 100644 > --- a/drivers/iio/common/ssp_sensors/ssp_spi.c > +++ b/drivers/iio/common/ssp_sensors/ssp_spi.c > @@ -277,12 +277,9 @@ static int ssp_handle_big_data(struct ssp_data *data, char *dataframe, int *idx) > static int ssp_parse_dataframe(struct ssp_data *data, char *dataframe, int len) > { > int idx, sd; > - struct timespec ts; > struct ssp_sensor_data *spd; > struct iio_dev **indio_devs = data->sensor_devs; > > - getnstimeofday(&ts); > - > for (idx = 0; idx < len;) { > switch (dataframe[idx++]) { > case SSP_MSG2AP_INST_BYPASS_DATA: > @@ -329,7 +326,7 @@ static int ssp_parse_dataframe(struct ssp_data *data, char *dataframe, int len) > } > > if (data->time_syncing) > - data->timestamp = ts.tv_sec * 1000000000ULL + ts.tv_nsec; > + data->timestamp = ktime_get_real_ns(); > > return 0; > }