From patchwork Sun Dec 31 19:55:54 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Stefan_Br=C3=BCns?= X-Patchwork-Id: 10138309 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 5920A6037D for ; Sun, 31 Dec 2017 19:56:16 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4614D288B6 for ; Sun, 31 Dec 2017 19:56:16 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3AC30288BC; Sun, 31 Dec 2017 19:56:16 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 53E2E288B6 for ; Sun, 31 Dec 2017 19:56:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750980AbdLaT4J (ORCPT ); Sun, 31 Dec 2017 14:56:09 -0500 Received: from mail-out-2.itc.rwth-aachen.de ([134.130.5.47]:59384 "EHLO mail-out-2.itc.rwth-aachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750923AbdLaT4I (ORCPT ); Sun, 31 Dec 2017 14:56:08 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: =?us-ascii?q?A2AKCwBgP0la/54agoZdHAEBAQQBAQoBA?= =?us-ascii?q?YM+ggEHhACZO4FamWYKhTsChDBDFAEBAQEBAQEBAWsohSQGIwQLAUYQJQImAgJ?= =?us-ascii?q?XBg4Fii4ErVOBbTqISoFlAQEBAQEFAQEBAQEjCQGBBYJ9ghKDaAyGKYRIDDGCZ?= =?us-ascii?q?QWKT5h9gROgNodpllYCAgICCQIagTw2IoFPcIJ6glQcgWh3iBsBgRUBAQE?= X-IPAS-Result: =?us-ascii?q?A2AKCwBgP0la/54agoZdHAEBAQQBAQoBAYM+ggEHhACZO4F?= =?us-ascii?q?amWYKhTsChDBDFAEBAQEBAQEBAWsohSQGIwQLAUYQJQImAgJXBg4Fii4ErVOBb?= =?us-ascii?q?TqISoFlAQEBAQEFAQEBAQEjCQGBBYJ9ghKDaAyGKYRIDDGCZQWKT5h9gROgNod?= =?us-ascii?q?pllYCAgICCQIagTw2IoFPcIJ6glQcgWh3iBsBgRUBAQE?= X-IronPort-AV: E=Sophos;i="5.45,486,1508796000"; d="scan'208";a="31524282" Received: from rwthex-w2-a.rwth-ad.de ([134.130.26.158]) by mail-in-2.itc.rwth-aachen.de with ESMTP; 31 Dec 2017 20:56:06 +0100 Received: from pebbles.fritz.box (77.182.71.79) by rwthex-w2-a.rwth-ad.de (2002:8682:1a9e::8682:1a9e) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1034.26; Sun, 31 Dec 2017 20:56:02 +0100 From: =?UTF-8?q?Stefan=20Br=C3=BCns?= To: CC: Peter Meerwald-Stadler , =?UTF-8?q?Stefan=20Br=C3=BCns?= , Maciej Purski , , "Andrew F . Davis" , Lars-Peter Clausen , Jonathan Cameron , Hartmut Knaack Subject: [PATCH v3 5/7] iio: adc: ina2xx: Use a monotonic clock for delay calculation Date: Sun, 31 Dec 2017 20:55:54 +0100 X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171229174806.5a615b63@archlinux> References: <20171229174806.5a615b63@archlinux> MIME-Version: 1.0 X-Originating-IP: [77.182.71.79] X-ClientProxiedBy: rwthex-s1-a.rwth-ad.de (2002:8682:1a98::8682:1a98) To rwthex-w2-a.rwth-ad.de (2002:8682:1a9e::8682:1a9e) Message-ID: <25c605b5-4206-4ed5-843b-37eaca79832f@rwthex-w2-a.rwth-ad.de> Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The iio timestamp clock is user selectable and may be non-monotonic. Also, only part of the acquisition time is measured, thus the delay was longer than intended. Use a monotonic timestamp to track the time for the next poll iteration. The timestamp is advanced by the sampling interval each iteration. In case the conversion overrruns the register readout (i.e. fast sampling combined with a slow bus), one or multiple samples will be dropped. Signed-off-by: Stefan Brüns --- Changes in v3: - use s64_div for 64 bit integer division to fix compiles on 32 bit archs Changes in v2: - add a comment mentioning skipping samples on overrun drivers/iio/adc/ina2xx-adc.c | 41 +++++++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 14 deletions(-) diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c index 2621a34ee5c6..64e9e8e1ad70 100644 --- a/drivers/iio/adc/ina2xx-adc.c +++ b/drivers/iio/adc/ina2xx-adc.c @@ -703,10 +703,10 @@ static int ina2xx_work_buffer(struct iio_dev *indio_dev) /* data buffer needs space for channel data and timestap */ unsigned short data[4 + sizeof(s64)/sizeof(short)]; int bit, ret, i = 0; - s64 time_a, time_b; + s64 time; unsigned int alert; - time_a = iio_get_time_ns(indio_dev); + time = iio_get_time_ns(indio_dev); /* * Because the timer thread and the chip conversion clock @@ -752,11 +752,9 @@ static int ina2xx_work_buffer(struct iio_dev *indio_dev) data[i++] = val; } - time_b = iio_get_time_ns(indio_dev); + iio_push_to_buffers_with_timestamp(indio_dev, data, time); - iio_push_to_buffers_with_timestamp(indio_dev, data, time_a); - - return (unsigned long)(time_b - time_a) / 1000; + return 0; }; static int ina2xx_capture_thread(void *data) @@ -764,7 +762,9 @@ static int ina2xx_capture_thread(void *data) struct iio_dev *indio_dev = data; struct ina2xx_chip_info *chip = iio_priv(indio_dev); int sampling_us = SAMPLING_PERIOD(chip); - int buffer_us, delay_us; + int ret; + struct timespec64 next, now, delta; + s64 delay_us; /* * Poll a bit faster than the chip internal Fs, in case @@ -773,15 +773,28 @@ static int ina2xx_capture_thread(void *data) if (!chip->allow_async_readout) sampling_us -= 200; + ktime_get_ts64(&next); + do { - buffer_us = ina2xx_work_buffer(indio_dev); - if (buffer_us < 0) - return buffer_us; + ret = ina2xx_work_buffer(indio_dev); + if (ret < 0) + return ret; - if (sampling_us > buffer_us) { - delay_us = sampling_us - buffer_us; - usleep_range(delay_us, (delay_us * 3) >> 1); - } + ktime_get_ts64(&now); + + /* + * Advance the timestamp for the next poll by one sampling + * interval, and sleep for the remainder (next - now) + * In case "next" has already passed, the interval is added + * multiple times, i.e. samples are dropped. + */ + do { + timespec64_add_ns(&next, 1000 * sampling_us); + delta = timespec64_sub(next, now); + delay_us = s64_div(timespec64_to_ns(&delta), 1000); + } while (delay_us <= 0); + + usleep_range(delay_us, (delay_us * 3) >> 1); } while (!kthread_should_stop());