Re: [PATCH v2 2/2] dma-contiguous: Use fallback alloc_pages for single pages

Masahiro Yamada
2019-08-29T11:47:04Z

On Wed, Aug 28, 2019 at 9:23 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> On Wed, Aug 28, 2019 at 7:53 PM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
> >
> > Hi Christoph,
> >
> > On Tue, Aug 27, 2019 at 8:55 PM Christoph Hellwig <hch@lst.de> wrote:
> > >
> > > On Tue, Aug 27, 2019 at 06:03:14PM +0900, Masahiro Yamada wrote:
> > > > Yes, this makes my driver working again
> > > > when CONFIG_DMA_CMA=y.
> > > >
> > > >
> > > > If I apply the following, my driver gets back working
> > > > irrespective of CONFIG_DMA_CMA.
> > >
> > > That sounds a lot like the device simply isn't 64-bit DMA capable, and
> > > previously always got CMA allocations under the limit it actually
> > > supported. I suggest that you submit this quirk to the mmc maintainers.
> >
> >
> > I tested v5.2 and my MMC host controller works with
> > dma_address that exceeds 32-bit physical address.
> >
> > So, I believe my MMC device is 64-bit DMA capable.
> >
> > I am still looking into the code
> > to find out what was changed.
>
>
> I retract this comment.
>
> Prior to bd2e75633c8012fc8a7431c82fda66237133bf7e,
> the descriptor table for ADMA is placed within the
> 32-bit phys address range, not exceeds the 32-bit limit.
>
> Probably, my device is not 64-bit capable.
>
> I will talk to the hardware engineer,
> and check the hardware spec just in case.
>

After looking more into my hardware,
I found out how to fix my driver:
https://lore.kernel.org/patchwork/patch/1121600/

--
Best Regards
Masahiro Yamada