# Re: \[PATCH 06/12\] dma-mapping: improve selection of dma\_declare\_coherent availability

- From: Christoph Hellwig \<hch@lst.de\>
- Date: 2019-02-13 18:24:39 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2019/02/5513423
- Thread: https://ratatoskr.run/linux-arm-kernel/2019/02/5509108/t.md

```text
On Tue, Feb 12, 2019 at 02:40:23PM -0600, Rob Herring wrote:
> > diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
> > index 3607fd2810e4..f8c66a9472a4 100644
> > --- a/drivers/of/Kconfig
> > +++ b/drivers/of/Kconfig
> > @@ -43,6 +43,7 @@ config OF_FLATTREE
> >
> >  config OF_EARLY_FLATTREE
> >         bool
> > +       select DMA_DECLARE_COHERENT
> 
> Is selecting DMA_DECLARE_COHERENT okay on UML? We run the unittests with UML.

No, that will fail with undefined references to memunmap.

I gues this needs to be

	select DMA_DECLARE_COHERENT if HAS_DMA

> Maybe we should just get rid of OF_RESERVED_MEM. If we support booting
> from DT, then it should always be enabled anyways.

Fine with me.  Do you want me to respin the series to just remove
it?
```