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Subject: Re: [PATCH 2/5] iommu/mediatek: Add mt8173 IOMMU driver
From: Yingjoe Chen <yingjoe.chen@mediatek.com>
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Date: Mon, 9 Mar 2015 22:46:29 +0800
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On Mon, 2015-03-09 at 20:11 +0900, Tomasz Figa wrote:
<...>
> > +/*
> > + * pimudev is a global var for dma_alloc_coherent.
> > + * It is not accepatable, we will delete it if "domain_alloc" is enabled
> > + */
> > +static struct device *pimudev;
> 
> This is indeed not acceptable. Could you replace dma_alloc_coherent()
> with something that doesn't require device pointer, e.g.
> alloc_pages()? (Although that would require you to handle cache
> maintenance in the driver, due to cached memory allocated.) I need to
> think about a better solution for this.

Hi,

For 2nd level page table, we use cached memory now. Currently we are
using __dma_flush_range to flush the cache, which is also unacceptable.

For proper cache management, we'll need to use dma_map_single or
dma_sync_*, which still need a deivce*.

Joe.C