From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-wr0-f177.google.com ([209.85.128.177]:35723 "EHLO mail-wr0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752709AbdHULha (ORCPT ); Mon, 21 Aug 2017 07:37:30 -0400 Received: by mail-wr0-f177.google.com with SMTP id k46so21768240wre.2 for ; Mon, 21 Aug 2017 04:37:30 -0700 (PDT) Subject: Re: [PATCH 1/7 v2] media: vb2: add bidirectional flag in vb2_queue To: Hans Verkuil , Marek Szyprowski , Mauro Carvalho Chehab Cc: Pawel Osciak , Kyungmin Park , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org References: <20170818141606.4835-2-stanimir.varbanov@linaro.org> <20170821090909.32614-1-stanimir.varbanov@linaro.org> From: Stanimir Varbanov Message-ID: <7122444e-a3e5-2fde-f608-a6b2f87eac29@linaro.org> Date: Mon, 21 Aug 2017 14:37:27 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi, On 08/21/2017 01:21 PM, Hans Verkuil wrote: > On 08/21/2017 11:29 AM, Marek Szyprowski wrote: >> Hi Stanimir, >> >> On 2017-08-21 11:09, Stanimir Varbanov wrote: >>> This change is intended to give to the v4l2 drivers a choice to >>> change the default behavior of the v4l2-core DMA mapping direction >>> from DMA_TO/FROM_DEVICE (depending on the buffer type CAPTURE or >>> OUTPUT) to DMA_BIDIRECTIONAL during queue_init time. >>> >>> Initially the issue with DMA mapping direction has been found in >>> Venus encoder driver where the hardware (firmware side) adds few >>> lines padding on bottom of the image buffer, and the consequence >>> is triggering of IOMMU protection faults. >>> >>> This will help supporting venus encoder (and probably other drivers >>> in the future) which wants to map output type of buffers as >>> read/write. >>> >>> Signed-off-by: Stanimir Varbanov >> >> This has been already discussed about a year ago, but it got lost in >> meantime, probably due to lack of users. I hope that this time it >> finally will get into vb2. >> >> For the reference, see https://patchwork.kernel.org/patch/9388163/ > > Interesting. > > Stanimir, I like your implementation better than the macro in the old > patch. But as it said there, videobuf2-dma-sg/contig/vmalloc.c have references > to DMA_FROM_DEVICE that won't work with BIDIRECTIONAL, so those need > to be adapted as well. I missed that when I reviewed your patch :-( Thanks for catching this, I didn't thought too much about usrptr. Sent v3. -- regards, Stan