From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 37F661096F; Thu, 9 Oct 2025 00:26:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759969615; cv=none; b=nxYl0Wuf+mxSh8nbKREYg3T+u+dUKaWlmaySyl/Hq8+9JJIEhOcvNK2453K/oGnHD6Nb2ynvFZXdlbZl5LzLWJCvYuMGDvIIy9nNc4PqC4Kn0nOW1hhdytjYRzVezS4GAWO2TVf7cKznluqbW3TZtcErag2h3oh8V4H3jiP/GrM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759969615; c=relaxed/simple; bh=NTZOj9046h7xAft3krHWfXm/mCYPdn9MS2UGaxNZUto=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kF2lQYh0cuZyhX5N7Ac66d7ehFOCUnmDLi12yap26E/tFDSyjJGyxsijLfwkkEXPw+/83vjW2n+NRZylvBIkWaoQq5vYL1Wev4y6gETf7varWuhOdTEktuPqvqueeRbu1vZbTs5kfSTgj9F5MLWZSBVt4yJ3oh7YOMOgGMRw+ro= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=goMbxqXr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="goMbxqXr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1B9B4C4CEE7; Thu, 9 Oct 2025 00:26:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759969614; bh=NTZOj9046h7xAft3krHWfXm/mCYPdn9MS2UGaxNZUto=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=goMbxqXr4MWFYmCePEx7Xg7V26wqq/gs4vIWNe6wIVggKbHkW6+DqbcHi7tDvtRIF 9DaPYBpQo6B3Ifc3a0UHmNX8ALV68uPzznohRAJYjG73s0PYWsp8uTbxd5qut1l1X9 4EPPtzxg/sclnOPdqMi5WlsEdvvlNEbhveL9e136Krg9LogQwbojJzLVmDTkHiVyMv jx8mWIP7Lru8RL+IniPW8vMu+ggm12zs1QPjkmvxP9dDZ2Mp6Plc1VnSA/rdWgx/cW 7D661dH39RjFrztPPG3688LFI69WRL2DzeEXISx5/08OjrmeUe8mhFfVGH1Q/LtlUg uuT9qTCKUfCZA== Message-ID: <1d36569c-55b9-4390-87d1-fd0c2f837014@kernel.org> Date: Thu, 9 Oct 2025 09:26:43 +0900 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: [RFC PATCH 0/3] Introduce iommu-map-masked for platform devices To: Rob Herring , Charan Teja Kalla Cc: joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, saravanak@google.com, conor+dt@kernel.org, mchehab@kernel.org, bod@kernel.org, krzk+dt@kernel.org, abhinav.kumar@linux.dev, vikash.garodia@oss.qualcomm.com, dikshita.agarwal@oss.qualcomm.com, linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev References: <20250928171718.436440-1-charan.kalla@oss.qualcomm.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 29/09/2025 05:23, Rob Herring wrote: > On Sun, Sep 28, 2025 at 12:17 PM Charan Teja Kalla > wrote: >> >> This series introduces a new iommu property called iommu-map-masked(may >> be there is a better name), which is used to represent the IOMMU >> specifier pairs for each function of a __multi-functional platform >> device__, where each function can emit unique master id(s) that can be >> associated with individual translation context. >> >> Currently, the iommu configuration - at least for arm architecture- >> requires all the functions of a platform device will be represented >> under single dt node thus endup in using only a single translation >> context. >> >> A simple solution to associate individual translation context for each >> function of a device can be through creating per function child nodes in >> the device tree, but dt is only to just represent the soc layout to >> linux kernel. >> >> Supporting such cases requires a new iommu property called, >> iommu-map-masked(taking cue from iommu-map for pci devices) and syntax >> is: >> iommu-map-masked = , >> ; >> NOTE: As an RFC, it is considered that this property always expects 4 >> cells. >> >> During the probe phase of the driver for a multi-functional device >> behind an IOMMU, a child device is instantiated for each FUNCTION_ID. >> The call to of_dma_configure_id() on each child sets up the IOMMU >> configuration, ensuring that each function of the device is associated >> with a distinct translation context. >> >> This property can also be used in association with 'iommus=' when dt >> bindings requires the presence of 'iommus=', example[2]. For these >> cases, representation will be(on arm64): >> iommus = <&iommu sid mask>; //for default function. >> iommu-map-masked = ;//additional >> function. > > Where does the FUNCTION_ID value come from? > > Why can't you just have multiple "iommus" entries where the index > defines the default and any FUNCTION_ID entries? What's in each index > is specific to the device. We discussed the problem earlier and that is what I asked them to do. Apparently I was just ignored so now two maintainers say the same. We can get ignored still and the third maintainer will have to tell this. Best regards, Krzysztof