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

Masahiro Yamada
2019-08-28T12:24:56Z

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.

Thanks.

--
Best Regards
Masahiro Yamada