From: eric.y.miao@gmail.com (Eric Miao)
To: linux-arm-kernel@lists.infradead.org
Subject: CONSISTENT_DMA_SIZE limitations
Date: Wed, 28 Apr 2010 14:47:02 +0800 [thread overview]
Message-ID: <n2rf17812d71004272347m63c1f3f3k71005f720110822e@mail.gmail.com> (raw)
In-Reply-To: <v2taec7e5c31004272325x9e5958ddp34d7db1ff3477f4d@mail.gmail.com>
On Wed, Apr 28, 2010 at 2:25 PM, Magnus Damm <magnus.damm@gmail.com> wrote:
> Hi everyone,
>
> Are there any special CONSISTENT_DMA_SIZE limitiations in the latest
> upstrem ARM kernel?
>
> On SH-Mobile ARM a single 256 MB I/O window is mapped virt:phys 1:1 at
> 0xe6000000 -> 0xf5ffffff at ->map_io() time.
>
> The virtual area on top of the I/O window at 0xf6000000 -> 0xffdfffff
> seems suitable for consistent dma mappings. Extending
> CONSISTENT_DMA_SIZE from the default 2MB to 158 MB makes efficient use
> of the entire range. Empty 2MB space is left at the top as usual.
>
> Extending CONSISTENT_DMA_SIZE seems like a good idea to me, but I'm
> not sure if doing so will break something else. Perhaps I need to
> rework some code in arch/arm/mm/dma-mapping.c?
>
Hi Magnus,
For a hackish way of enabling something, I don't think that's a bad idea
to extend CONSISTENT_DMA_SIZE. And it's often seen by framebuffer
and video/graphics related drivers, which is normally hungry for large
amount of consistent memory. However, I'm a little bit concerned about
such usage, (esp. I'm not sure how this is done in ARMv7), my preference
would be:
1) either use the dma API
2) or reserve a large chunk of memory during boot and get it remapped later
> I'm asking because most platforms only export up to 14 MB, and
> Documentation/arm/memory.txt mentions 0xff000000 -> 0xffbfffff as
> reserved.
>
> Thanks!
>
> / magnus
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
next prev parent reply other threads:[~2010-04-28 6:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-28 6:25 CONSISTENT_DMA_SIZE limitations Magnus Damm
2010-04-28 6:47 ` Eric Miao [this message]
2010-04-28 7:07 ` Shilimkar, Santosh
2010-04-28 7:53 ` Magnus Damm
2010-04-28 7:08 ` Magnus Damm
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=n2rf17812d71004272347m63c1f3f3k71005f720110822e@mail.gmail.com \
--to=eric.y.miao@gmail.com \
--cc=linux-arm-kernel@lists.infradead.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).