Re: [PATCH 2/2] arm-nommu: Add use_reserved_mem() to check if device support reserved memory

[dillon min]

Hi Vladimir,

I tested your changes, it's working fine on stm32f429-disco(armv7m,
without cache) board.
you can submit a separate patch for dma-direct support on non-mmu
platform, i will drop mine.

thanks.

best regards.

Dillon,
On Wed, Jun 10, 2020 at 1:34 AM Christoph Hellwig <hch@xxxxxx> wrote:
>
> On Tue, Jun 09, 2020 at 05:25:04PM +0100, Vladimir Murzin wrote:
> > Even though commit mentions ARM, I do not see how mmap would continue
> > to work for NOMMU with dma-direct. ARM NOMMU needs it's own DMA operations
> > only in cases where caches are implemented or active, in other cases it
> > fully relies on dma-direct.
>
> > It looks to me that we either should provide NOMMU variant for mmap in
> > dma/direct or (carefully) fix dma/mapping.
>
> I think dma-direct is the right place, the common helpers in
> dma/mapping.c are basically the red headed stepchilds for misc
> IOMMU drivers not covered by dma-iommu only.

Yes, thanks Christoph's input.