linux-kernel - Re: [PATCH v5 2/3] media: dt-bindings: media: mediatek: Remove "dma-ranges" property for decoder

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Date:   Mon, 5 Dec 2022 17:32:14 -0300
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Allen-KH Cheng <allen-kh.cheng@...iatek.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, yunfei.dong@...iatek.com
Subject: Re: [PATCH v5 2/3] media: dt-bindings: media: mediatek: Remove
 "dma-ranges" property for decoder

On Mon, Nov 28, 2022 at 10:38:31PM +0800, Allen-KH Cheng wrote:
> Since commit f1ad5338a4d5 ("of: Fix "dma-ranges" handling for bus
> controllers") was merge, we don't need a dma-ranges property for IOMMU
> in mediatek video codec.

This description isn't right, as it gives the impression that the mentioned
commit removed the need for having a dma-ranges property, but that isn't the
case, the property wasn't needed even before that commit. That commit did
however expose the fact that having this property didn't make sense in the first
place.

Here's a suggestion:

	The decoder nodes already make use of the iommus property to configure the IOMMU
	for address translations, so also having a dma-ranges property doesn't make
	sense.

	In fact, after commit f1ad5338a4d5 ("of: Fix "dma-ranges" handling for bus
	controllers"), having a dma-ranges property causes IOMMU faults.

	Remove the dma-ranges property and update the example.

Reviewed-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

Thanks,
Nícolas