linux-kernel - Re: [PATCH v2 2/2] dma-contiguous: Use fallback alloc

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Date:   Wed, 28 Aug 2019 21:23:43 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Nicolin Chen <nicoleotsuka@...il.com>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>, vdumpa@...dia.com,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Tony Lindgren <tony@...mide.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Thierry Reding <treding@...dia.com>,
        Kees Cook <keescook@...omium.org>, iamjoonsoo.kim@....com,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-xtensa@...ux-xtensa.org, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v2 2/2] dma-contiguous: Use fallback alloc_pages for
 single pages

On Wed, Aug 28, 2019 at 7:53 PM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> Hi Christoph,
>
> On Tue, Aug 27, 2019 at 8:55 PM Christoph Hellwig <hch@....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