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=-17.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham 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 0E491C47082 for ; Sat, 5 Jun 2021 14:00:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE24A610C8 for ; Sat, 5 Jun 2021 14:00:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229958AbhFEOCW (ORCPT ); Sat, 5 Jun 2021 10:02:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:40762 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229930AbhFEOCW (ORCPT ); Sat, 5 Jun 2021 10:02:22 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CD96B61354; Sat, 5 Jun 2021 14:00:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622901634; bh=hxclUIZzpdL+w/09+qsOdmrX2Z93cV8AWpuZ+eHpEC8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=QMJqjbdkdB6mV/GMB9yRBqizuiYmMaXHOW0CPOKDXqI+mpqScS6uLdASA7+g9+PcI XBYrL4nNK9Up82F8tf/YHQyLAtn6sK7FchxntwCzvtyUuVltrp6yHQDyI6TU4rIkQm 1m+Q6tykoagz2EiwQEVwENtnChPc+y0qYMFSo7Xa5Hdzlqfg14U0RSjenSXRVcL5kz IImFiZYyE1oJCVJ/Ea2ihZ7ZGbnJW0Qio7bZHfFuBNsCwD/BJy5X6Yh5T/qa54jWma epsmZazPA/l4VLdQA5O3ncjajINo0DWi8RaqSSEwIsJKyUpc0hAL6/WxgRJOXTZ8ov 2Or98LXFWJr+A== Date: Sat, 5 Jun 2021 16:00:28 +0200 From: Mauro Carvalho Chehab To: Seongyong Park Cc: linux-media@vger.kernel.org, Matt Ranostay Subject: Re: [PATCH 1/2] media: video-i2c: frame delay based on last frame's end time Message-ID: <20210605160028.6ec30b8a@coco.lan> In-Reply-To: <20210605115456.14440-2-euphoriccatface@gmail.com> References: <20210605115456.14440-1-euphoriccatface@gmail.com> <20210605115456.14440-2-euphoriccatface@gmail.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-redhat-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-media@vger.kernel.org Em Sat, 5 Jun 2021 20:54:56 +0900 Seongyong Park escreveu: > Current implementation calculates frame delay based on the time of > start of the loop. This inevitably causes the loop delay to be > slightly longer than the actual measurement period, thus skipping a frame > every now and then. > > However, MLX90640 should ideally be working without a frame skip. > Each measurement step updates half of the pixels in the frame > (every other pixel in default "chess mode", and every other row > in "interleave mode"), while additional coefficient data (25th & 26th row) > updates every step. The compensational coefficient data only corresponds > with the pixels updated in the same step. > > In short, if a frame is skipped, then half of a frame loses correction > information and becomes garbage data. > > Signed-off-by: Seongyong Park > --- > drivers/media/i2c/video-i2c.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/drivers/media/i2c/video-i2c.c b/drivers/media/i2c/video-i2c.c > index 0465832a4..2ccb08335 100644 > --- a/drivers/media/i2c/video-i2c.c > +++ b/drivers/media/i2c/video-i2c.c > @@ -445,14 +445,16 @@ static int video_i2c_thread_vid_cap(void *priv) > struct video_i2c_data *data = priv; > unsigned int delay = mult_frac(HZ, data->frame_interval.numerator, > data->frame_interval.denominator); > + unsigned long end_jiffies = jiffies; > > set_freezable(); > > do { > - unsigned long start_jiffies = jiffies; > struct video_i2c_buffer *vid_cap_buf = NULL; > int schedule_delay; > > + end_jiffies += delay; > + > try_to_freeze(); > > spin_lock(&data->slock); > @@ -477,10 +479,9 @@ static int video_i2c_thread_vid_cap(void *priv) > VB2_BUF_STATE_ERROR : VB2_BUF_STATE_DONE); > } > > - schedule_delay = delay - (jiffies - start_jiffies); > - > - if (time_after(jiffies, start_jiffies + delay)) > - schedule_delay = delay; > + schedule_delay = end_jiffies - jiffies; > + while (schedule_delay <= 0) > + schedule_delay += delay; Huh? Why do you need a loop for that? If you want to make it positive, you could just do: if (schedule_delay < 0) schedule_delay = delay; /* or something else */ but this won't solve the issue, as this is basically equivalent to the logic you removed. > > schedule_timeout_interruptible(schedule_delay); This is probably what's causing troubles, as this only ensures that it will sleep for at least schedule_delay (if not interrupted). If you want to give a dead line to schedule, you should likely be doing, instead: usleep_range(delay, delay + delta); this would tell the realtime clock that there's a dead line of (schedule_delay + delta) microseconds. You'll need to change the delay to be in microseconds too, e. g., I guess that something similar to this: static int video_i2c_thread_vid_cap(void *priv) { struct video_i2c_data *data = priv; u64 delay; delay = div64_u64(1000000ULL * data->frame_interval.numerator, data->frame_interval.denominator); set_freezable(); do { ... usleep_range(delay * 3 / 4, delay); } while (!kthread_should_stop()); return 0; } would give you what you want. Regards, Mauro