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

From: Yong Wu <[email-masked]>
Date: Sat, 22 May 2021 17:50:59 +0800

On Fri, 2021-05-21 at 16:06 +0800, Tzung-Bi Shih wrote:
> On Fri, May 21, 2021 at 3:02 PM Irui Wang <[email-masked]> 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/[email-masked]/
> 
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