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

From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
	Tony Lindgren <tony@atomide.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Max Filippov <jcmvbkbc@gmail.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Russell King <linux@armlinux.org.uk>,
	Thierry Reding <treding@nvidia.com>,
	linux-xtensa@linux-xtensa.org, Kees Cook <keescook@chromium.org>,
	Nicolin Chen <nicoleotsuka@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Chris Zankel <chris@zankel.net>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	David Woodhouse <dwmw2@infradead.org>,
	linux-mmc <linux-mmc@vger.kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	iommu@lists.linux-foundation.org, iamjoonsoo.kim@lge.com,
	Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v2 2/2] dma-contiguous: Use fallback alloc_pages for single pages
Date: Tue, 27 Aug 2019 18:03:14 +0900	[thread overview]
Message-ID: <CAK7LNAQZ+bueZZzSoMADmgLjWNvijHRV=wLQzN_kvLG3b5Uu+w@mail.gmail.com> (raw)
In-Reply-To: <20190827075021.GA953@lst.de>

On Tue, Aug 27, 2019 at 4:50 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Tue, Aug 27, 2019 at 04:45:20PM +0900, Masahiro Yamada wrote:
> > On Mon, Aug 26, 2019 at 4:33 PM Christoph Hellwig <hch@lst.de> wrote:
> > >
> > > On Mon, Aug 26, 2019 at 11:05:00AM +0900, Masahiro Yamada wrote:
> > > > This is included in v5.3-rc6
> > > > so I tested it.
> > >
> > > So there is no allocation failure, but you get I/O errors later?
> >
> > Right.
> >
> > >
> > > Does the device use a device-private CMA area?
> >
> > Not sure.
> > My driver is drivers/mmc/host/sdhci-cadence.c
> > It reuses routines in drivers/mmc/host/sdhci.c
> >
> >
> >
> > >  Does it work with Linux
> > > 5.2 if CONFIG_DMA_CMA is disabled?
> >
> > No.
> > 5.2 + disable CONFIG_DMA_CMA
> > failed in the same way.
>
> So it seems like the device wants CMA memory.   I guess the patch
> below will fix it, but that isn't the solution.  Can you try it
> to confirm?  In the end it probably assumes a dma mask it doesn't
> set that the CMA memory satisfies or something similar.


Thanks for the pointer.


> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> index 69cfb4345388..bd2f24aa7f19 100644
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -236,7 +236,7 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
>
>         if (dev && dev->cma_area)
>                 cma = dev->cma_area;
> -       else if (count > 1)
> +       else
>                 cma = dma_contiguous_default_area;
>
>         /* CMA can be used only in the context which permits sleeping */

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.

diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
index 163d1cf4367e..504459395c39 100644
--- a/drivers/mmc/host/sdhci-cadence.c
+++ b/drivers/mmc/host/sdhci-cadence.c
@@ -237,6 +237,7 @@ static const struct sdhci_ops sdhci_cdns_ops = {

 static const struct sdhci_pltfm_data sdhci_cdns_pltfm_data = {
        .ops = &sdhci_cdns_ops,
+       .quirks2 = SDHCI_QUIRK2_BROKEN_64_BIT_DMA,
 };

 static int sdhci_cdns_set_tune_val(struct sdhci_host *host, unsigned int val)







-- 
Best Regards
Masahiro Yamada
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