From: Arnd Bergmann <arnd@arndb.de>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Will Deacon <Will.Deacon@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Ding Tianhong <dingtianhong@huawei.com>
Subject: Re: For the problem when using swiotlb
Date: Mon, 24 Nov 2014 21:12:09 +0100 [thread overview]
Message-ID: <2166613.l2i4mdmtLA@wuerfel> (raw)
In-Reply-To: <20141121180925.GG19783@e104818-lin.cambridge.arm.com>
On Friday 21 November 2014 18:09:25 Catalin Marinas wrote:
> On Fri, Nov 21, 2014 at 05:51:19PM +0000, Catalin Marinas wrote:
> > On Fri, Nov 21, 2014 at 05:04:28PM +0000, Arnd Bergmann wrote:
> > > On Friday 21 November 2014 16:57:09 Catalin Marinas wrote:
> > > > There is a scenario where smaller mask would work on arm64. For example
> > > > Juno, you can have 2GB of RAM in the 32-bit phys range (starting at
> > > > 0x80000000). A device with 31-bit mask and a dma_pfn_offset of
> > > > 0x80000000 would still work (there isn't any but just as an example). So
> > > > the check in dma_alloc_coherent() would be something like:
> > > >
> > > > phys_to_dma(top of ZONE_DMA) - dma_pfn_offset <= coherent_dma_mask
> > > >
> > > > (or assuming RAM starts at 0 and ignoring dma_pfn_offset for now)
> > > >
> > > > If the condition above fails, dma_alloc_coherent() would no longer fall
> > > > back to swiotlb but issue a dev_warn() and return NULL.
> > >
> > > Ah, that looks like it should work on all architectures, very nice.
> > > How about checking this condition, and then printing a small warning
> > > (dev_warn, not WARN_ON) and setting the dma_mask pointer to NULL?
> >
> > I would not add the above ZONE_DMA check to of_dma_configure(). For
> > example on arm64, we may not support a small coherent_dma_mask but the
> > same value for dma_mask could be fine via swiotlb bouncing (or IOMMU).
> > However, that's an arch-specific decision. Maybe after the above setting
> > of dev->coherent_dma_mask in of_dma_configure(), we could add:
> >
You seem to implement the opposite:
> + /*
> + * If the bus dma-ranges property specifies a size smaller than 4GB,
> + * the device would not be capable of accessing the whole 32-bit
> + * space, so reduce the default coherent_dma_mask accordingly.
> + */
> + if (size && size < (1ULL << 32))
> + dev->coherent_dma_mask = DMA_BIT_MASK(ilog2(size));
> +
> + /*
> + * Set dma_mask to coherent_dma_mask by default if the architecture
> + * code has not set it and DMA on such mask is supported.
> + */
> + if (!dev->dma_mask && dma_supported(dev, dev->coherent_dma_mask))
> + dev->dma_mask = &dev->coherent_dma_mask;
> }
>
Here, coherent_dma_mask wouldn't work while dma_mask might be
fine in case of swiotlb, but you set a nonzero coherent_dma_mask
and an invalid dma_mask.
Arnd
next prev parent reply other threads:[~2014-11-24 20:12 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-17 11:56 For the problem when using swiotlb Ding Tianhong
2014-11-17 12:18 ` Arnd Bergmann
2014-11-17 18:09 ` Catalin Marinas
2014-11-19 3:17 ` Ding Tianhong
2014-11-19 8:45 ` Arnd Bergmann
2014-11-19 11:29 ` Catalin Marinas
2014-11-19 12:48 ` Arnd Bergmann
2014-11-19 15:46 ` Catalin Marinas
2014-11-19 15:56 ` Arnd Bergmann
2014-11-21 11:06 ` Catalin Marinas
2014-11-21 11:26 ` Arnd Bergmann
2014-11-21 11:36 ` Catalin Marinas
2014-11-21 12:27 ` Arnd Bergmann
2014-11-20 2:57 ` Ding Tianhong
2014-11-20 7:40 ` Arnd Bergmann
2014-11-20 8:34 ` Ding Tianhong
2014-11-20 9:02 ` Arnd Bergmann
2014-11-20 9:21 ` Ding Tianhong
2014-11-21 9:35 ` Catalin Marinas
2014-11-21 10:32 ` Catalin Marinas
2014-11-21 12:48 ` Arnd Bergmann
2014-11-21 16:57 ` Catalin Marinas
2014-11-21 17:04 ` Arnd Bergmann
2014-11-21 17:51 ` Catalin Marinas
2014-11-21 18:09 ` Catalin Marinas
2014-11-24 20:12 ` Arnd Bergmann [this message]
2014-11-25 10:58 ` Catalin Marinas
2014-11-25 11:29 ` Russell King - ARM Linux
2014-11-25 12:23 ` Catalin Marinas
2014-11-27 2:36 ` Ding Tianhong
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2166613.l2i4mdmtLA@wuerfel \
--to=arnd@arndb.de \
--cc=Will.Deacon@arm.com \
--cc=catalin.marinas@arm.com \
--cc=dingtianhong@huawei.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).