linux-kernel - Re: [PATCH 1/5] dt-bindings: media: mtk-vcodec: Add dma-ranges property

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Date:   Mon, 1 Mar 2021 14:45:29 +0800
From:   Irui Wang <irui.wang@...iatek.com>
To:     Rob Herring <robh@...nel.org>
CC:     Alexandre Courbot <acourbot@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Fritz Koenig" <frkoenig@...omium.org>,
        Tzung-Bi Shih <tzungbi@...omium.org>,
        Maoguang Meng <maoguang.meng@...iatek.com>,
        Longfei Wang <longfei.wang@...iatek.com>,
        Yunfei Dong <yunfei.dong@...iatek.com>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH 1/5] dt-bindings: media: mtk-vcodec: Add dma-ranges
 property

On Wed, 2021-02-10 at 16:53 -0600, Rob Herring wrote:
> On Wed, Feb 03, 2021 at 04:37:48PM +0800, Irui Wang wrote:
> > Adds dma-ranges property for DMA addresses translation.
> > 
> > Signed-off-by: Irui Wang <irui.wang@...iatek.com>
> > ---
> >  Documentation/devicetree/bindings/media/mediatek-vcodec.txt | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/media/mediatek-vcodec.txt b/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> > index f85276e629bf..e4644f8caee9 100644
> > --- a/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> > +++ b/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> > @@ -23,6 +23,8 @@ Required properties:
> >  - iommus : should point to the respective IOMMU block with master port as
> >    argument, see Documentation/devicetree/bindings/iommu/mediatek,iommu.txt
> >    for details.
> > +- dma-ranges : describes how the physical address space of the IOMMU maps
> > +  to memory.
> 
> dma-ranges is supposed to be in a bus/parent node.
Dear Rob,

The mt8192 iommu support 0~16GB iova. We separate it to four banks:
0~4G; 4G~8G; 8G~12G; 12G~16G.

The "dma-ranges" could be used to adjust the bank we locate.
If we don't set this property. The default range always is 0~4G.

Here we don't have actual bus/parent concept here.  And the iova
requirement is for our HW. Thus put the property in our node.

Is this OK? If this is ok for you, I will put this message in the commit
message and binding in next version.

Regards
> 
> >  One of the two following nodes:
> >  - mediatek,vpu : the node of the video processor unit, if using VPU.
> >  - mediatek,scp : the node of the SCP unit, if using SCP.
> > -- 
> > 2.25.1
> >