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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 27552C2D0EC for ; Tue, 7 Apr 2020 23:59:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F15D720720 for ; Tue, 7 Apr 2020 23:59:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="dmHuwCoU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726512AbgDGX67 (ORCPT ); Tue, 7 Apr 2020 19:58:59 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:18946 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726407AbgDGX66 (ORCPT ); Tue, 7 Apr 2020 19:58:58 -0400 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 07 Apr 2020 16:57:14 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Tue, 07 Apr 2020 16:58:57 -0700 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Tue, 07 Apr 2020 16:58:57 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL109.nvidia.com (172.20.187.15) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 7 Apr 2020 23:58:56 +0000 Received: from [10.2.171.175] (10.124.1.5) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 7 Apr 2020 23:57:43 +0000 Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver From: Sowjanya Komatineni To: Dmitry Osipenko , , , , , , CC: , , , , , References: <1585963507-12610-1-git-send-email-skomatineni@nvidia.com> <23bfab09-b464-6e51-9843-06d13000e9b9@nvidia.com> <08cd31d5-e8b9-4d3a-fb0e-0e4462947d96@nvidia.com> <12a834ac-52b1-6dc0-7d3a-3e6a1fa85a2a@gmail.com>

<760d071e-0cbc-b3eb-9231-fb9f9ecb44a6@nvidia.com> <9e317f65-8a02-3b15-cfec-8e0d8374130e@gmail.com> <97b35910-4c93-123a-43a0-eb14476ed0f3@nvidia.com> <84ad4e2d-6ac1-e1f4-1c55-5edaae850631@nvidia.com> <15a879b3-8fb9-6821-3cdc-104ba583ac12@gmail.com> <0c425505-347f-7418-af7e-d121fe0d06dc@nvidia.com> <1a31cd60-739f-0660-1c45-31487d2f2128@nvidia.com> <603084a5-249a-4fe2-3646-e9335ef9ab43@nvidia.com> Message-ID: Date: Tue, 7 Apr 2020 16:57:42 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <603084a5-249a-4fe2-3646-e9335ef9ab43@nvidia.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) 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=1586303834; bh=WYYijVJNHfLwjTCH3gNwu8d4A+RLe1YduJ1izGmTGaY=; 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=dmHuwCoULE5BLIDblMLpSgxcHMBKRoftC7H99Z24OQk02WAtj0mCIdy8eQcXX9D2Q CxFpEwlTzVR9sNKcB/tmSyT6VW0af0UGqw1ifekOjAodceqhNYfEi8n3/6FYqSAH4/ iOCZJReh/KRpbzI0frdMT3rH8OibhzX4Qnioyi12vqeCir3uW0ve7+i6nspHvwptrH 2IlU8dnpB3Q6zTkLqoy3yKwdDWO5kNBO+01i1jlIrBehRX85Cy7fbG3wC5YqpDe7f0 U+1KysPlnIpdD8OqQH6AOpvU+54+64jf4P7LbWEpx1tiN+3BCaDlEl8SmZuap1IM3y onRaRvqcBcnMw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/7/20 4:38 PM, Sowjanya Komatineni wrote: > > On 4/7/20 4:36 PM, Sowjanya Komatineni wrote: >> >> On 4/7/20 4:12 PM, Dmitry Osipenko wrote: >>> External email: Use caution opening links or attachments >>> >>> >>> 08.04.2020 01:22, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>> On 4/7/20 3:08 PM, Dmitry Osipenko wrote: >>>>> External email: Use caution opening links or attachments >>>>> >>>>> >>>>> 08.04.2020 00:08, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>>> ... >>>>>>>> I think you need a semaphore with resource count =3D 2. >>>>>>> we hold on to issuing capture if more than 2 buffers are queued=20 >>>>>>> and it >>>>>>> continues only after fifo has min 1 slot empty >>>>>> Just want to close on this part of feedback. Hope above=20 >>>>>> explanation is >>>>>> clear regarding triggering/issuing at max 2 frame capture to VI=20 >>>>>> HW and >>>>>> also regarding capture threads where they use=20 >>>>>> wait_event_interruptible >>>>>> to prevent blocking waiting for buffers to be available for=20 >>>>>> captures. >>>>>> >>>>>> So no changes related to this part are needed in v7. >>>>> =C2=A0 From what I see in the code, you "hold on" by making kthread t= o=20 >>>>> spin in >>>>> a busy-loop while caps_inflight >=3D SYNCPT_FIFO_DEPTH. So some chang= e >>>>> should be needed to prevent this. >>>>> >>>>> The wait_event_interruptible seems should be okay. >>>> We don't want to prevent that as we already have buffers available for >>>> capture so as soon as VI HW issuing single shot is done and when min 1 >>>> slot is empty we should continue with issuing for another capture. >>>> >>>> As long as buffers are available, we should continue to capture and >>>> should not hold >>>> >>> I suppose that taking a shot takes at least few milliseconds, which >>> should be unacceptable to waste. >> As long as buffers are in queue we have to keep processing each=20 >> buffer and between buffers obviously we have to wait for previous=20 >> frames to finish and this why we have separate thread for frame=20 >> finish where we can have next buffer capture ready and issue while=20 >> previous frame memory write happens Also we specified numbers buffers as 3 to vb2 queue. So this is rare=20 case but to prevent issuing more than 2 at a time as VI HW is only=20 double buffered and syncpt fifo max depth is 2 added this to be safer.