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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 6FC85C432BE for ; Tue, 3 Aug 2021 08:12:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5307F60F35 for ; Tue, 3 Aug 2021 08:12:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234435AbhHCIMi (ORCPT ); Tue, 3 Aug 2021 04:12:38 -0400 Received: from lb2-smtp-cloud8.xs4all.net ([194.109.24.25]:36927 "EHLO lb2-smtp-cloud8.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234248AbhHCIMf (ORCPT ); Tue, 3 Aug 2021 04:12:35 -0400 Received: from cust-b5b5937f ([IPv6:fc0c:c16d:66b8:757f:c639:739b:9d66:799d]) by smtp-cloud8.xs4all.net with ESMTPA id ApXCmT3NXXTlcApXDmkLwO; Tue, 03 Aug 2021 10:12:23 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xs4all.nl; s=s2; t=1627978343; bh=nJAT4/TY9kAvr0jgZL4sTyPUkvxuezWK4PADS7XhJmE=; h=Subject:To:From:Message-ID:Date:MIME-Version:Content-Type:From: Subject; b=s4P2peHCmMtkOB6hlRicbMb/PhZ5RiRVCJADXDKDXkWXsHiokl8y5MshvaVg7S4Et AmPFV7DewYB4gsPWPAt9EYIKv92gvslx5MSV9lCIGOAbfIAmL/11ctTvLzRRS/oHa7 aTsYUvYbiH13jSMHILR0Y6BKXLG7hh7mmZ74eLt0UGag3/KBcW3ew6H8fUgesWuvqh 7/pdo9B8c9UIMsFjoHooBH8+Uo8OqccnvnETbDKNKINby5xxABvqGHAgc99U9hE7P8 8+FvbO6qf7EkAVXYp7NuWyQtxCUsl8KkyYrYL8QZHSMNWIWL5qhIHXQSH1C9iPD8h7 3QauOTpZiPCaw== Subject: Re: [PATCHv4 5/8] videobuf2: add V4L2_MEMORY_FLAG_NON_COHERENT flag To: Sergey Senozhatsky , Tomasz Figa Cc: Dafna Hirschfeld , Ricardo Ribalda , Christoph Hellwig , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210727070517.443167-1-senozhatsky@chromium.org> <20210727070517.443167-6-senozhatsky@chromium.org> From: Hans Verkuil Message-ID: <45dbd3f1-778b-eb6c-94b3-51e8a92429b6@xs4all.nl> Date: Tue, 3 Aug 2021 10:12:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210727070517.443167-6-senozhatsky@chromium.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4xfL9glTvDB4IJVNjXR/BbbplpliCXT7ZRiUm3ex+DKhuzQvOevne25CJdJ0yxy2idMFon6V9BnducT0FYnzUwcn+EELFJb5A+8IsC0eRllSqYpmVLpHuG yWWpm2YRkcTy0eBjb0qV+YTJn8iJ/t838Km1ZJ3TNTmztldLdfyEBNLewZoTdhQbgg9R5x1O7IRhEQzhs7SF2KJ13tPEbpcv/O7XO50FthJrM5usAtE6YYGE yESOIXrUw+XvJEtlF4+1N0nimaCcPgpneeKyd3r1iX+L/PAmalu3mafiMlFOVtYqgQc7nwi3MOM9DWYg2IMVsYplQY6nQdRV+KPkgrGF7dhp1mocLOZokEat iG8OqoTjjvhojmhJz39iBeEJiaBCGFBa1zXdPauSZBiMun0t1cRLd+rdjlLQW8Yf11jiTzV9zNvw4dKQUGc8TvRL4fZXL2P5K02IxU7vUAnm0hYww0IZYO4P CTpfRsevLMXEreFB8HQLjdSVWZOFaKYGxbsmTcgrO6owPAgm74DNATDAUVX4vN6gmjg12JWSJ+sDNyip Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/07/2021 09:05, Sergey Senozhatsky wrote: > By setting or clearing V4L2_MEMORY_FLAG_NON_COHERENT flag clearing -> clearing the > user-space should be able to hint vb2 that either a non-coherent either a -> either > (if supported) or coherent memory should be used for the buffer > allocation. Regards, Hans > > Signed-off-by: Sergey Senozhatsky > --- > .../userspace-api/media/v4l/buffer.rst | 40 ++++++++++++++++++- > .../media/v4l/vidioc-reqbufs.rst | 5 ++- > include/uapi/linux/videodev2.h | 2 + > 3 files changed, 43 insertions(+), 4 deletions(-) > > diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst > index e991ba73d873..4638ec64db00 100644 > --- a/Documentation/userspace-api/media/v4l/buffer.rst > +++ b/Documentation/userspace-api/media/v4l/buffer.rst > @@ -676,8 +676,6 @@ Buffer Flags > > \normalsize > > -.. _memory-flags: > - > enum v4l2_memory > ================ > > @@ -701,6 +699,44 @@ enum v4l2_memory > - 4 > - The buffer is used for :ref:`DMA shared buffer ` I/O. > > +.. _memory-flags: > + > +Memory Consistency Flags > +------------------------ > + > +.. raw:: latex > + > + \small > + > +.. tabularcolumns:: |p{7.0cm}|p{2.1cm}|p{8.4cm}| > + > +.. cssclass:: longtable > + > +.. flat-table:: > + :header-rows: 0 > + :stub-columns: 0 > + :widths: 3 1 4 > + > + * .. _`V4L2-MEMORY-FLAG-NON-COHERENT`: > + > + - ``V4L2_MEMORY_FLAG_NON_COHERENT`` > + - 0x00000001 > + - A buffer is allocated either in coherent (it will be automatically > + coherent between the CPU and the bus) or non-coherent memory. The > + latter can provide performance gains, for instance the CPU cache > + sync/flush operations can be avoided if the buffer is accessed by the > + corresponding device only and the CPU does not read/write to/from that > + buffer. However, this requires extra care from the driver -- it must > + guarantee memory consistency by issuing a cache flush/sync when > + consistency is needed. If this flag is set V4L2 will attempt to > + allocate the buffer in non-coherent memory. The flag takes effect > + only if the buffer is used for :ref:`memory mapping ` I/O and the > + queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS > + ` capability. > + > +.. raw:: latex > + > + \normalsize > > Timecodes > ========= > diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst > index 50ea72043bb0..e59306aba2b0 100644 > --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst > +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst > @@ -158,8 +158,9 @@ aborting or finishing any DMA in progress, an implicit > - This capability is set by the driver to indicate that the queue supports > cache and memory management hints. However, it's only valid when the > queue is used for :ref:`memory mapping ` streaming I/O. See > - :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE ` and > - :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN `. > + :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE `, > + :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN ` and > + :ref:`V4L2_MEMORY_FLAG_NON_COHERENT `. > > .. raw:: latex > > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > index 9260791b8438..9d11e1d9c934 100644 > --- a/include/uapi/linux/videodev2.h > +++ b/include/uapi/linux/videodev2.h > @@ -956,6 +956,8 @@ struct v4l2_requestbuffers { > __u32 reserved[1]; > }; > > +#define V4L2_MEMORY_FLAG_NON_COHERENT (1 << 0) > + > /* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */ > #define V4L2_BUF_CAP_SUPPORTS_MMAP (1 << 0) > #define V4L2_BUF_CAP_SUPPORTS_USERPTR (1 << 1) >