linux-kernel - Re: [PATCH v4,3/6] media: mtk-vcodec: Support 4GB~8GB range iova space for venc

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Date:   Sat, 22 May 2021 17:50:59 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Tzung-Bi Shih <tzungbi@...gle.com>
CC:     Irui Wang <irui.wang@...iatek.com>,
        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>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomasz Figa <tfiga@...gle.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Maoguang Meng <maoguang.meng@...iatek.com>,
        "Longfei Wang" <longfei.wang@...iatek.com>,
        Yunfei Dong <yunfei.dong@...iatek.com>,
        Fritz Koenig <frkoenig@...omium.org>,
        Tzung-Bi Shih <tzungbi@...omium.org>,
        <linux-media@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
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        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
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        <linux-arm-kernel@...ts.infradead.org>,
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        <linux-mediatek@...ts.infradead.org>,
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Subject: Re: [PATCH v4,3/6] media: mtk-vcodec: Support 4GB~8GB range iova
 space for venc

On Fri, 2021-05-21 at 16:06 +0800, Tzung-Bi Shih wrote:
> On Fri, May 21, 2021 at 3:02 PM Irui Wang <irui.wang@...iatek.com> wrote:
> > +       if (of_get_property(pdev->dev.of_node, "dma-ranges", NULL))
> > +               dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(34));
> > +
> 
> From your previous dt-bindings patch[1], it has 4 banks.
> > 0~4G; 4G~8G; 8G~12G; 12G~16G.
> 
> But, the code treats it as a boolean.  I.e. 0~4GB if non-existent;
> otherwise, 4GB~8GB.

Here DMA_BIT_MASK(34) means dma address support 34bits(16GB).

The code is ok for me. Only the commit message should not say 4G-8G. it
could be something like:

Use the dma_set_mask_and_coherent helper to set venc DMA bit mask to
support 34bits iova space(16GB) that the mt8192 iommu HW support. Whole
the iova range separate to 0~4G/4G~8G/8G~12G/12G~16G, Regarding which
iova range VENC actually locate, it depend on the dma-ranges property of
the venc dtsi node.

> 
> [1]: https://patchwork.linuxtv.org/project/linux-media/patch/20210521070139.20644-3-irui.wang@mediatek.com/
> 
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