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 8BFD431C567; Thu, 8 Oct 2026 22:58:55 +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=1791500336; cv=none; b=RjNHYxdIHXNcoDEyZHpkJfZT1p+wzP6l/QWgIsiDN4xm1GBkUFzLiWQPWjfjIEhr8rjeulp0BNYwA0L55I8GeXQfNiZ76VI7BSLQjE7EvIqXkAottNMdRsUrisRFWVr+T4YX7Ga9g8lUNHS+1bGBk4JeEntSWc8Q1BGSLCPyW1E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791500336; c=relaxed/simple; bh=Etn31UNku7VCsJLoEXol2PzDljV1RmMABZd3Im1OZYM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VdWPTydrhOiAul4/U2pfaZ3THXg+dXzG4TbhHjvd/rDAieh13+u9RRj2UPwxrgWNUbAg+2hEX0A7TUkuQKzone9jZC5Q92t3XCMWgeSeDu8C2GFmo8XPBZG8v/MuAhS5WhYXzphCqKxLKtBH56NeWYGR1ZVtXTHTXTHXYnKMRjU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mx5lVjhK; 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="mx5lVjhK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 329221F000FF; Thu, 8 Oct 2026 22:58:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791500335; bh=4dyYpzzqWX64rhPXAppTWubez23gpMFqzDA0FYPPM6o=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=mx5lVjhKlkAPc7pNGHfFdLepNOmkjA0EnqfXcX1UjaMemOqPDxpnmzkNUKGcYncMk TTs3YFNCV5a/TQIU05YB4ID0U+7+w4PYcPzL0UhXLvnDQQA/AqZrPkGJdynmHJ2SV+ JjcM55O7alNZvtGXzlXjTJSptt3H8tDGgNyqvff9O33JO7pFLERp4rnM0baAIrq4HY ME0Gdc9EpzrHOTWC/HrffGrujB2rT6FKnXSso6x2qeQZWtH/Wst6STs6uaa67EEg6F GL5olwoaEFD6XKKXm3K+MQb+Uk38oKvNw9dKCy9QuCLXncHy6wKos/ideIdok7HUx1 BLQiys+0iiK3Q== Message-ID: Date: Thu, 8 Oct 2026 23:58:48 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 02/13] dt-bindings: media: qcom,sm8550-iris: Add context bank subnodes To: Vikash Garodia , Dikshita Agarwal , Abhinav Kumar , Mauro Carvalho Chehab , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Stanimir Varbanov , Neil Armstrong , Dmitry Baryshkov , Bryan O'Donoghue , Stephan Gerhold , "Joerg Roedel (AMD)" , Will Deacon , Robin Murphy , Abel Vesa Cc: linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Konrad Dybcio , Krzysztof Kozlowski , iommu@lists.linux.dev, Krzysztof Kozlowski , Vishnu Reddy References: <20260926-vpu_iommu_iova_handling-v5-0-0322ca5dc10c@oss.qualcomm.com> <20260926-vpu_iommu_iova_handling-v5-2-0322ca5dc10c@oss.qualcomm.com> From: Bryan O'Donoghue Content-Language: en-GB Autocrypt: addr=bod@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 26/09/2026 07:34, Vikash Garodia wrote: > The VPU issues DMA through several SMMU streams, and the hardware does > not give every stream the same addressable range. The non-pixel stream > cannot address the low 600MB of IOVA space, while the pixel stream can > address the full range: > +-----------------------------------------------------------+ > | non-pixel stream addressable range (600 MB - 3.5 GB) | > | 0x25800000 - 0xe0000000 | > +-----------------------------------------------------------+ > | pixel stream addressable range (0 - 3.5 GB) | > | 0x00000000 - 0xe0000000 | > +-----------------------------------------------------------+ > A single "iommus" property on the video-codec node puts every stream in > one IOMMU domain sharing one IOVA allocator, so nothing restricts a > non-pixel buffer to avoid 0 to 600MB. Once an allocation lands below > that boundary the hardware faults, which shows up as unhandled SMMU page > faults and spontaneous reboots: > https://gitlab.freedesktop.org/drm/msm/-/work_items/100 > > Given that the address range restriction is for specific VPU stream, it > should be ideally be moved to that stream. To achieve the same, a subset > of streams is now represented as subnodes, so that each can be > associated with its respective addressable range. The design was > discussed and agreed by mainatiners here > https://lore.kernel.org/all/c7b956a9-d3e8-4e18-b780-5d08f5cd2ca1@kernel.org > > In the past, this limitation was addressed with an iommu-map approach, > with the iris driver dynamically creating the devices. That approach was > later concluded to be a hack to avoid having subnodes, and was NAKed by > the iommu maintainers. It was discussed in detail here: > https://lore.kernel.org/all/c7b956a9-d3e8-4e18-b780-5d08f5cd2ca1@kernel.org/ > > Update example to the subnode form. Doing so, it picks up the supporting > properties needed on the video-codec node, address-cells, size-cells and > dma-ranges to declare 1:1 DMA translation into the parent. > > Reviewed-by: Krzysztof Kozlowski > Co-developed-by: Vishnu Reddy > Signed-off-by: Vishnu Reddy > Signed-off-by: Vikash Garodia Reviewed-by: Bryan O'Donoghue