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 C5AA13F3286; Thu, 6 Aug 2026 09:36:54 +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=1786009016; cv=none; b=jx43wNo4zKr5fvAwGWid/c7vIuNrmjRVQtpD5etGikFYc20iD8rzpMi7L5KSXfqUkHXFKjRWWAghEZFafCK8jTdgwAQfbBxYwgtBp2vEKDiHQdP7u2JKc/ozzPI5PIxTbBIuOQSK6Ma3Y4QMGWc9XnekTTjXPHGcr5fA/lr5fgg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786009016; c=relaxed/simple; bh=/9Q5cG8ldbWnfIdg/Wv2LI2RYtQy4M3JgGt631OvMTI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mEk5GXgqtkp/WCIGxD64pVlacgXN6Sqjzt1BsYhCMbGqHBoc/V9a+b9p4ap51YyqnQd2GFejcWO18tQSEQm4x+JsvnuhM/SaDrkbxhguQTnyzEij6MGn4dlibHAErx+J1kwCFOTV/CItjVQchOWm7PvfuDyYzv9G4pz+vWIYw8k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=n5VLFUn1; 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="n5VLFUn1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 419E91F00A3A; Thu, 6 Aug 2026 09:36:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786009013; bh=rdPdqJV4mQ10FVUkWhMaqcDT56k5KTr7Ol9Micjxtf0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=n5VLFUn1qPcd7F41K0Bk8ZxLGk7G/Meyn99kZEhB2bsx6COgjrbp2Gu2wnHNsSPGs PwiTSmHY9KLvPb9P1l+5Oaa2wkCtJhuUPcSAWfqrHCxCQ9pLiqadhHWxISiI7oex5z AigrxvSIkw1A+DOM5Aerr1m60B2cF98+kG/ic3HTyr4QZU0cwmWvkCTIdgEi3RRi7V 0HXhBzcrcqetsgyFAkIFW22ewfeRAvLbuwgRHTHmoUNa6/FBjA4i94rqJ5xw6Pr54j BSF1OgrWnlfPdeUv1zDnxfLObiSlG/v3hayVNwLSoTMUQ+mQhHdws0Xt2p5pnkNkaj Pa/nxdPpPb34g== Message-ID: <9921567d-4b3a-43b6-bf5e-eb0e92102e34@kernel.org> Date: Thu, 6 Aug 2026 11:36:45 +0200 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 v2 01/12] dt-bindings: media: qcom,venus: Add context bank subnodes to common schema To: Dmitry Baryshkov Cc: Vikash Garodia , Dikshita Agarwal , Abhinav Kumar , Bryan O'Donoghue , Mauro Carvalho Chehab , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Stanimir Varbanov , Neil Armstrong , Bryan O'Donoghue , Stephan Gerhold , linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Konrad Dybcio , stable@vger.kernel.org, Daniel J Blueman References: <20260731-vpu_iommu_iova_handling-v2-0-da52b5228dbd@oss.qualcomm.com> <20260731-vpu_iommu_iova_handling-v2-1-da52b5228dbd@oss.qualcomm.com> <20260805-dark-voracious-jacamar-6aae4c@quoll> <7a546bc6-a2b4-457d-ac27-05fc1cfe17f5@kernel.org> <163c24ba-6b78-44bb-afe9-3dcbb4d47475@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 06/08/2026 11:22, Dmitry Baryshkov wrote: > On Thu, Aug 06, 2026 at 11:11:09AM +0200, Krzysztof Kozlowski wrote: >> On 06/08/2026 10:46, Dmitry Baryshkov wrote: >>> >>>> dma-ranges tell how this bus - so venus/iris - performs DMA translation >>>> in respective to parent. Address/size-cells are obviously also needed if >>>> this is a bus with addressing. >>>> >>>> But there are no children with addressing, thus what sort of bus would >>>> it be? >>>> >>>> It looks to me that having here both: >>>> 1. dma-ranges + address/size-cells >>>> 2. children without bus addressing >>>> is some sort of abuse of the DT syntax. It is allowed, but does not >>>> really represent hardware. >>>> >>>> IOW, dma-ranges alone feels okay, although unusual, and it states proper >>>> DMA translation for this bus. If you add address/size-cells, it means >>>> this bus HAS addressing and thus YOU MUST use addressing. >>>> >>>> If my understanding is correct, then solution would be to add addressing >>>> to the children (so unit address and "reg" property) or drop >>>> address/size-cells as Rob pointed out. [1] >>> >>> Doesn't dma-ranges require address/size cells? In the end, how can you >> >> I think it does not require, at least how I understood the DT spec, >> unless you provide actual addresses to the property. >> >> IOW, this requires address/size-cells: >> dma-ranges = <0 0 0 0 0x10 0>; >> >>> specify the DMA address if the device doesn't have addressing at all (or >>> MMIO-style addressing)? >> >> Yeah, that's why having here children without bus addressing is >> confusing. I would interpret it that, children are not on MMIO bus, thus >> the venus/iris is some sort of proprietary bus with no mapping between >> parent MMIO and children nodes. >> >> If there is no mapping, then we do not have 'ranges' property. But I >> could imagine that such no-mapping bus still provides access to system RAM? >> >> Actually this feels like a huge stretch, so I tend to think that the >> only reasonable option is to have children with MMIO, which would make >> it explicit: Venus/iris is a bus which provides translation of both MMIO >> and DMA addresses to the parent. > > But there are no separate addresses for those subnodes. Would you prefer There might be some or maybe these should be the addresses of DMA? > them to duplicate the addresses of the parent node? Or would the > 'ranges' be enough? I made mistake earlier - 'dma-ranges' without values is not described in DT spec explicitly, but should be treated as 'ranges' without values, thus direct mapping from parent to the child. So it also requires address/size-cells, just like 'dma-ranges = '. And dtc checks/reports that. I think therefore now that the binding is unusual (because no bus addresses of children) but actually correct. > > Or, thinking about it, if Venus / Iris have 32-bit addressing, then > dma-range should probably define the limited DMA range. That's another point which I also raised to Vikash already - mapping should be restricted to 32-bit if this is how the child devices operate. Best regards, Krzysztof