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 49C6C38552F; Tue, 3 Mar 2026 08:57:34 +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=1772528254; cv=none; b=CVbCJ03iSCQkCs9SovR1B9TQkPX4cX4gVHx3cVHxrCLfA58xcCdwgPsyGix5pT/SMaShzXjI6+XwqcXWZwI+C4MNOVgktdGlLmo3/T2I6qAzOu3D7KbiWDOgL7XPnSV/t/JycGNrL9UBGJpKIyVnuD0X/Ms11k8UFgpC//ZvGJk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772528254; c=relaxed/simple; bh=KulhFkadCwBsmVUEcbSD4peLvLMdzJNrHT+Iiz3ob9A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mPHk+qAarjzxTZ4wBDLfXKl2J4C22RXxwAkxu9hWglC+CJcvCQyJrbPfKRDKAK0NCeww9/MAaf0/9M/NJooR+R5z3klqW8zDfO8kWREaI4NyBsU0ySXc1j8q4xM2yO97cYT0Kqk1GiJvA3+tkRJkSOWamiwD6qOlfNJXF/WJ4Fs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rU+Ih78T; 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="rU+Ih78T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5E76C19425; Tue, 3 Mar 2026 08:57:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772528254; bh=KulhFkadCwBsmVUEcbSD4peLvLMdzJNrHT+Iiz3ob9A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=rU+Ih78T7EOoLYCGqRgx6jNA22Fi92dBiAxVgB/yNJ4xXHGjsjGynQjkVicwZzaA1 I5r3k1XYoyN/7PAbzYMvwkMsCj9oSBsRV7sOlPn0oTmXWQ2m9MYMxIkmgmKIAoCeBt 9QJZ3Iqrw+KwEvPFJhUBA/nMIUtAr8sgzulSkpyD21c/sH8q2Diw7UxS4R3sKxnHC5 8xWdcpBp6wKnOowaDNUHj/OjSaVa+ih/lsH7L9uwrY5E46odlltoIlUuCqKbZCN1wp UtF+aBQaL+412kW7FfFS7xEWvwizsPQ/kc8QugLRPZgY0iAlGF0YMyFp3KXb4/gtsc VFoFf1TxZjOwg== Message-ID: Date: Tue, 3 Mar 2026 09:57:29 +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 v2 1/9] dt-bindings: dma: nvidia,tegra186-gpc-dma: Add iommu-map property To: Akhil R Cc: Frank.Li@kernel.org, conor+dt@kernel.org, devicetree@vger.kernel.org, dmaengine@vger.kernel.org, jonathanh@nvidia.com, krzk+dt@kernel.org, ldewangan@nvidia.com, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, p.zabel@pengutronix.de, robh@kernel.org, thierry.reding@kernel.org, vkoul@kernel.org References: <20260303-famous-fearless-asp-1240cb@quoll> <20260303084005.57114-1-akhilrajeev@nvidia.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 03/03/2026 09:40, Akhil R wrote: > On Tue, 3 Mar 2026 07:39:58 +0100 Krzysztof Kozlowski wrote: >> On Mon, Mar 02, 2026 at 06:02:31PM +0530, Akhil R wrote: >>> Add iommu-map property to specify separate stream IDs for each DMA >>> channel. This enables each channel to be in its own IOMMU domain, >>> keeping memory isolated from other devices sharing the same DMA >>> controller. >>> >>> Signed-off-by: Akhil R >>> --- >>> .../devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml b/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml >>> index 0dabe9bbb219..1e7b5ddd4658 100644 >>> --- a/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml >>> +++ b/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml >>> @@ -14,6 +14,7 @@ description: | >>> maintainers: >>> - Jon Hunter >>> - Rajesh Gumasta >>> + - Akhil R >>> >>> allOf: >>> - $ref: dma-controller.yaml# >>> @@ -51,6 +52,10 @@ properties: >>> iommus: >>> maxItems: 1 >>> >>> + iommu-map: >>> + minItems: 1 >>> + maxItems: 32 >> >> Why is this flexible? If it is, means usually items are distinctive, so >> I would expect defining/listing them. If they are not distinctive, >> commit msg is incorrect. If the list is as simple as 1-to-1 channel >> mapping, just add it in the description how they are ordered. > > Yes, it is a 1-to-1 channel mapping to an IOMMU ID. The intent of making > it flexible is to allow non-consecutive IOMMU ID assignments as well. You cannot skip items if these have such meaning of mapping per channel. The list order is the ABI - index of the list is the channel here. > This is particularly needed in virtualised environments where the > hypervisor may reserve certain stream IDs, and the guest VM can map only > the permitted ones. Shall I add a description here mentioning this > use-case? You can also look at recent works for iris video codec from Qualcomm solving something similar. Best regards, Krzysztof