Received: by 2002:a25:1985:0:0:0:0:0 with SMTP id 127csp2312135ybz; Thu, 30 Apr 2020 14:56:56 -0700 (PDT) X-Google-Smtp-Source: APiQypL7iXmsAr60wWQgCK+7IIE/baT9iJZWf0k9WDvkTaIngNpFM4t67xxTzjSBW2BZ6RnnpscY X-Received: by 2002:a17:906:3f45:: with SMTP id f5mr565164ejj.18.1588283816147; Thu, 30 Apr 2020 14:56:56 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1588283816; cv=none; d=google.com; s=arc-20160816; b=GGsRc80+xeTL8xCA5f4AsCE+/qEq2lYRnA9n4s4XYnwjCIr3/TlLZ7U3pGVKwyYW3e QC6bw5VPvs7ZGwNMXB6LZbNZURH09QE4gEq++TCl8aKTcZO3+GckKt35feje/cpnc1v7 LJwWrHvpFxwdaMsVbDW8NkT/PKxmTSGe0z9evOx4LOI4EQAoxhUM7cIIvAc1JOH4EdAW xCIkRLKKe2ZgHK6aieK9btSNynne//YGu6YHk5YqqlXTSnQvPpKRpIKUuxjrQBF1Ez/p ixldd7QkLFU9USAlvGDNVSCc/asxaKOt+klAcQ4e8bOMWkTB6a+JMooDqQOTEYOFdR6A xWxg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:dkim-signature:content-language :content-transfer-encoding:in-reply-to:mime-version:user-agent:date :message-id:references:cc:to:from:subject; bh=di+O2jLI16ikEh7mcZPdM1oOPlVh7YwvDEgl3ofBFFY=; b=S6Lo5U9WP7UZOv18q8F+wtIY3+A6sh9cwJd+X0tcb11qDDaylKSffZTkWT8H97VP94 o/vhj7mPprGZUk9+Lzm6+M/aFryo8RpZChmTCNRylBJf3K64kgmuhJ06T6SZKfyjQs9Y eG23y8mCRip/bDiK3p1sQDpDN3SNtyShefgjyw4Ss5AHJ5ordWwD7Di1QYN+NjLrradB nekCob0Ku0v+bmI6reNNFcEyyBrd4GpOXeh1PbufYmRLxAI18hKHV8sV7RV7CbREHCyV yxY374y9hutnV/FaBAjw2XEJQFJuc89FBFvSWgs/QCKjSrytUmRiYEvTr9vzyXjZ480/ 0+Hw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=QUkm9BsY; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id ck25si612435ejb.114.2020.04.30.14.56.33; Thu, 30 Apr 2020 14:56:56 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=QUkm9BsY; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727929AbgD3VzQ (ORCPT + 99 others); Thu, 30 Apr 2020 17:55:16 -0400 Received: from hqnvemgate26.nvidia.com ([216.228.121.65]:16014 "EHLO hqnvemgate26.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbgD3VzP (ORCPT ); Thu, 30 Apr 2020 17:55:15 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 30 Apr 2020 14:55:02 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 30 Apr 2020 14:55:14 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 30 Apr 2020 14:55:14 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL111.nvidia.com (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 30 Apr 2020 21:55:14 +0000 Received: from [10.2.165.152] (10.124.1.5) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 30 Apr 2020 21:55:13 +0000 Subject: Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver From: Sowjanya Komatineni To: Dmitry Osipenko , , , , , , CC: , , , , , References: <1588197606-32124-1-git-send-email-skomatineni@nvidia.com> <1588197606-32124-7-git-send-email-skomatineni@nvidia.com> <4da289e6-036f-853b-beb4-379d6462adb0@gmail.com>

<7d31d24f-f353-7e82-3ff9-cdba8b773d1e@nvidia.com> <06a4a067-8d54-4322-b2a6-14e82eaeda29@nvidia.com> <47873bbd-cf90-4595-5a99-7e9113327ecc@nvidia.com> <71532440-f455-cc24-74f7-9ccad5947099@gmail.com> <298187f6-2425-4813-1ae1-f256c179623e@nvidia.com> <9c942bc9-703e-3bbb-eeab-f37e69dc1ded@nvidia.com> <668d9b65-9590-cc97-41c3-2c1a5cfbbe61@nvidia.com> <289d9c92-383f-3257-de7b-46179724285a@nvidia.com> Message-ID: <9aa64f21-7b23-7228-b5eb-d2ff092682ad@nvidia.com> Date: Thu, 30 Apr 2020 14:53:44 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <289d9c92-383f-3257-de7b-46179724285a@nvidia.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To DRHQMAIL107.nvidia.com (10.27.9.16) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Content-Language: en-US DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1588283702; bh=di+O2jLI16ikEh7mcZPdM1oOPlVh7YwvDEgl3ofBFFY=; h=X-PGP-Universal:Subject:From:To:CC:References:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Transfer-Encoding: Content-Language; b=QUkm9BsYCzLjJC9wwWzUoammOxqJhoV75L5/vcRflEVZPOAmDXeGeYyPX8t4Q0t9N unLxyTkfHHBU6p7GATpa6hKDaGo78v7c1LsKi5j6aDNjH8IGqSkfwBPNIj0VWhYK8Q luD033P9ilP9FZaXkIuNBi/TWP0iAjmR1S25VWwr4XMwZtNLlQCe1Ncvp6i2qvTcy7 zjDsMUAvSnIcAkJGahkgKcBdPFveWDPZfj4uMjGtQjUuKxFLlb1pqKApFtkoXzvNa4 E+qTYIIDdsLi3nBDGO4wUctaBZHV/IE8YNDXLcR1veA8JvHH58NOyYJn4EoYjlJgue 8aTMXmeLnFy9w== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/20 2:37 PM, Sowjanya Komatineni wrote: > > On 4/30/20 2:26 PM, Sowjanya Komatineni wrote: >> >> On 4/30/20 2:17 PM, Dmitry Osipenko wrote: >>> 30.04.2020 23:02, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>> On 4/30/20 12:53 PM, Sowjanya Komatineni wrote: >>>>> On 4/30/20 12:46 PM, Sowjanya Komatineni wrote: >>>>>> On 4/30/20 12:33 PM, Dmitry Osipenko wrote: >>>>>>> 30.04.2020 22:09, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1= =82: >>>>>>>> On 4/30/20 11:18 AM, Sowjanya Komatineni wrote: >>>>>>>>> On 4/30/20 10:06 AM, Sowjanya Komatineni wrote: >>>>>>>>>> On 4/30/20 9:29 AM, Sowjanya Komatineni wrote: >>>>>>>>>>> On 4/30/20 9:04 AM, Sowjanya Komatineni wrote: >>>>>>>>>>>> On 4/30/20 7:13 AM, Dmitry Osipenko wrote: >>>>>>>>>>>>> 30.04.2020 17:02, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1= =82: >>>>>>>>>>>>>> 30.04.2020 16:56, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5= =D1=82: >>>>>>>>>>>>>>> 30.04.2020 01:00, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0= =B5=D1=82: >>>>>>>>>>>>>>>> +static int chan_capture_kthread_finish(void *data) >>>>>>>>>>>>>>>> +{ >>>>>>>>>>>>>>>> +=C2=A0=C2=A0=C2=A0 struct tegra_vi_channel *chan =3D data= ; >>>>>>>>>>>>>>>> +=C2=A0=C2=A0=C2=A0 struct tegra_channel_buffer *buf; >>>>>>>>>>>>>>>> + >>>>>>>>>>>>>>>> +=C2=A0=C2=A0=C2=A0 set_freezable(); >>>>>>>>>>>>>>>> + >>>>>>>>>>>>>>>> +=C2=A0=C2=A0=C2=A0 while (1) { >>>>>>>>>>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 try_to_freeze(= ); >>>>>>>>>>>>>>> I guess it won't be great to freeze in the middle of a=20 >>>>>>>>>>>>>>> capture >>>>>>>>>>>>>>> process, so: >>>>>>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (= list_empty(&chan->done)) >>>>>>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 try_to_freeze(); >>>>>>>>>>>>>> And here should be some locking protection in order not race >>>>>>>>>>>>>> with >>>>>>>>>>>>>> the >>>>>>>>>>>>>> chan_capture_kthread_start because kthread_finish could=20 >>>>>>>>>>>>>> freeze >>>>>>>>>>>>>> before >>>>>>>>>>>>>> kthread_start. >>>>>>>>>>>>> Or maybe both start / finish threads should simply be=20 >>>>>>>>>>>>> allowed to >>>>>>>>>>>>> freeze >>>>>>>>>>>>> only when both capture and done lists are empty. >>>>>>>>>>>>> >>>>>>>>>>>>> if (list_empty(&chan->capture) && >>>>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 list_empty(&chan->done)) >>>>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0try_to_freeze(); >>>>>>>>>>>> good to freeze when not in middle of the frame capture but why >>>>>>>>>>>> should we not allow freeze in between captures? >>>>>>>>>>>> >>>>>>>>>>>> Other drivers do allow freeze in between frame captures. >>>>>>>>>>>> >>>>>>>>>>>> I guess we can freeze before dequeue for capture and in finish >>>>>>>>>>>> thread we can freeze after capture done. This also don't=20 >>>>>>>>>>>> need to >>>>>>>>>>>> check for list_empty with freeze to allow between frame=20 >>>>>>>>>>>> captures. >>>>>>>>>>>> >>>>>>>>>>> Also if we add check for both lists empty, freeze is not=20 >>>>>>>>>>> allowed as >>>>>>>>>>> long as streaming is going on and in case of continuous=20 >>>>>>>>>>> streaming >>>>>>>>>>> freeze will never happen. >>>>>>>>> To allow freeze b/w frames (but not in middle of a frame), >>>>>>>>> >>>>>>>>> for capture_start thread, probably we can do unconditional >>>>>>>>> try_to_freeze() >>>>>>> Is it possible to use wait_event_freezable()? >>>>>>> >>>>>>> https://www.kernel.org/doc/Documentation/power/freezing-of-tasks.tx= t=20 >>>>>>> >>>>>>> >>>>>>> Will the wait_event_interruptible() be woken up when system=20 >>>>>>> freezes? >>>>>> Based on wait_event_freezable implementation, looks like it similar >>>>>> to wait_event_interruptible + try_to_free() as it does >>>>>> freezable_schedule unlike schedule with wait_event_interruptible. >>>>>> >>>>>> So using this for capture_start may be ok to allow freeze before >>>>>> start of frame. But can't use for capture_finish as this is same as >>>>>> wait_event_interruptible followed by unconditional try_to_freeze. >>>>>> >>>>>>>>> for capture_finish thread, at end of capture done we can do >>>>>>>>> try_to_freeze() only when done list is empty >>>>>>> This doesn't prevent situation where the done-list is empty and the >>>>>>> "finish" thread freezes, in the same time the "start" thread=20 >>>>>>> issues new >>>>>>> capture and then freezes too. >>>>>>> >>>>>>> 1. "start" thread issues capture >>>>>>> >>>>>>> 2. "finish" thread wakes and waits for the capture to complete >>>>>>> >>>>>>> 3. "start" thread begins another capture, waits for FRAME_START >>>>>>> >>>>>>> 4. system freezing activates >>>>>>> >>>>>>> 5. "finish" thread completes the capture and freezes because=20 >>>>>>> done-list >>>>>>> is empty >>>>>>> >>>>>>> 6. "start" thread gets FRAME_START, issues another capture and=20 >>>>>>> freezes >>>>>> This will not happen as we allow double buffering done list will not >>>>>> be empty till stream stop happens >>>>>> >>>>>> There will always be 1 outstanding frame in done list >>>>> Correction, there will always be 1 outstanding buffer except=20 >>>>> beginning >>>>> during beginning of stream. >>>>> >>>>> Except during beginning frames, done list will not be empty for all >>>>> subsequent streaming process >>>> Also to be clear, hardware sees next frame start event prior to=20 >>>> previous >>>> frame mw_ack event as mw_ack event happens after frame end. So once >>>> initial buffer got queued to done list to finish processes, while >>>> waiting for mw_ack next frame start happens and pushes next buffer to >>>> done list. >>> What about this variant: >>> >>> 1. "start" thread wakes up to start capture >>> >>> 2. system freezing activates >>> >>> 3. "finish" thread wakes up and freezes >> >> finish thread will wake up only when done list is not=20 >> empty/kthread_stop/wake even from capture start thread. >> >> Also when I said will allow try_to_free when done list is empty I=20 >> meant to have this at end of capture_done() in finish thread >> >>> >>> 4. "start" thread issues capture and freezes >>> >>> And again, I assume that system's freezing should wake >>> wait_event_interruptible(), otherwise it won't be possible to freeze >>> idling threads at all and freezing should fail (IIUC). >> >> Based on kernel doc on freezing, looks like when we mark thread as=20 >> freezable, freeze state happens when we explicitly call try_to_freeze. >> >> I don't think its other way where freeze causes=20 >> wait_event_interruptible to wake up. Based on my understanding when we mark thread as freezable, with wait_event_freezable() - after wait event, it invokes=20 try_to_freeze(). So frozen state enters unconditionally with this. with wait_event_interruptible - we do try_to_freeze when its safe to=20 enter frozen state. https://www.kernel.org/doc/Documentation/power/freezing-of-tasks.txt >> >>> And in this case synchronization between start/finish threads should be >>> needed in regards to freezing. >> >> Was thinking to have counter to track outstanding frame w.r.t single=20 >> shot issue b/w start and finish and allow to freeze only when no=20 >> outstanding frames in process. >> >> This will make sure freeze will not happen when any buffers are in=20 >> progress >> >>> Note that this could be a wrong assumption, I'm not closely familiar >>> with how freezer works. > > kthread_start can unconditionally allow try_to_freeze before start of=20 > frame capture > > We can compute captures inflight w.r.t single shot issued during=20 > capture start and finished frames by kthread_finish and allow=20 > kthread_finish to freeze only when captures inflight is 0. > > This allows freeze to happen b/w frames but not in middle of frame > >