From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 26372395AE2; Thu, 13 Aug 2026 09:19:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786612764; cv=none; b=tabu2+dZqb8HAoSlDnxG5dO3j2QT96xdSDjek8ZR/5PuTjH8Av0/0P2wV9ExjPfzZy9TVwNkwfeJMvAF0UNcrRFecJN0FkRgV07jQZBOeelQexJuD5BAxPqVCcBCvsnJndvFlDdaGzrqFArjv/R45Z4YfIXEmyELSvR/GdBg4Oo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786612764; c=relaxed/simple; bh=Rvlb7d3DPVUO7Rfg/xBsTOVbCksTf2KV0DpMm1IVZm8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kW+QE/Ye3aj6BIdBVHl/9M80GsEvmzUxHgCk+SU2aCEjCzCKoLpiojEJyvB4PS6tquxL+TxuUbxBVQAaIvSUasU5yv8MMR7fXSi8gXbVtimvtOobTN67j0y74eab4y8MBEyQ8E3ZRPhek/Cahai4tGrRwIvxKHSlagft/tlho5A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jaYTaSeR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jaYTaSeR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D7EF1F000E9; Thu, 13 Aug 2026 09:19:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786612762; bh=GUbO6EHJZBA9Gb3pwMZqnqkK8tW44x4tkSu21Kl/zb4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=jaYTaSeR3VOJwqy6bt12Os4MdE953BmT3uquBsYvLODJLuE7OLPn6qtJ9jL6p5kc1 46eRqaOTMEQphlGbCnFcKi1LIDPnvqq0/yez/BR08XnjFC/5kJqeohArDWiLodTGx9 mn03W0AM39Ht8NSbisjdcisNicSZdj9FcRmqTfEmReDWKaRBHZMeemZpwLiVDUhBKV KhSfMsgfDb/6F6O2dbGHeX56O39YHGPUifImpiIe1M++jPqkrfelEyfJx6hKhIN0Zu uHaYw4d//lIm+bY+GvafkMI1QTrl2UFFf78o1qjwXKA/kMzr7EFRa1PMNbf24O5RxJ EWQJQn86IsLCA== Date: Thu, 13 Aug 2026 11:19:10 +0200 From: Krzysztof Kozlowski To: Vishnu Reddy Cc: Bryan O'Donoghue , Vikash Garodia , Dikshita Agarwal , Mauro Carvalho Chehab , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Stanimir Varbanov , Mansur Alisha Shaik , Bjorn Andersson , Konrad Dybcio , Abhinav Kumar , Hans Verkuil , Stefan Schmidt , Hans Verkuil , linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/4] dt-bindings: media: qcom,sc7280-venus: Add dma-coherent property Message-ID: <20260813-prompt-peculiar-chimera-7d7dab@quoll> References: <20260801-iris-fixes-dma-pseq-fint-v1-0-aba0cb22f6ab@oss.qualcomm.com> <20260801-iris-fixes-dma-pseq-fint-v1-1-aba0cb22f6ab@oss.qualcomm.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260801-iris-fixes-dma-pseq-fint-v1-1-aba0cb22f6ab@oss.qualcomm.com> On Sat, Aug 01, 2026 at 01:07:27PM +0530, Vishnu Reddy wrote: > While testing with some higher resolution clips, the venus hardware > triggers a fault due to wrong input data being received. Corruption > was also observed in the captured output when the client dumped it > to a file. > > On debugging, this was traced to the venus node not declaring > dma-coherent. As a result, DMA buffers shared between the CPU and the > venus video hardware/controller are not guaranteed to be I/O coherent: > CPU writes to an input buffer can remain in CPU caches without being > visible to the video hardware when it reads the same buffer, so the > hardware receives input data that does not match what the CPU wrote. > Likewise, on the capture path, data written by the video hardware to > the output buffer may not be visible to the CPU, so the client reads > stale or partial data, resulting in corruption. > > Add the dma-coherent property to the venus node so that DMA buffers > shared between the CPU and the video hardware and controller remain > coherent. This is confusing - dma-coherent saves you from syncing the buffers, so how could it solve the issue? You basically skip certain cache sync operations, not add them. Best regards, Krzysztof