From: arnd@arndb•de (Arnd Bergmann)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: relax conditions required for enabling Contiguous Memory Allocator
Date: Mon, 20 Aug 2012 20:01:23 +0000 [thread overview]
Message-ID: <201208202001.23443.arnd@arndb.de> (raw)
In-Reply-To: <1345443372-3824-1-git-send-email-m.szyprowski@samsung.com>
On Monday 20 August 2012, Marek Szyprowski wrote:
> Contiguous Memory Allocator requires only paging and MMU enabled not
> particular CPU architectures, so there is no need for strict dependency
> on CPU type. This enables to use CMA on some older ARM v5 systems which
> also might need large contiguous blocks for the multimedia processing hw
> modules.
>
> Reported-by: Prabhakar Lad <prabhakar.csengg@gmail•com>
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung•com>
The patch looks simple, but I want a better explanation for it.
When we went through all possible cases, we decided that:
* ARMv6+ need CMA to avoid the double mapping problem.
* ARMv4/v5 cannot generally use CMA because it doesn't work
together with DMABOUNCE. I don't remember if it was the
only problem, but I definitely remember this was intentional.
* We want a common kernel for all ARMv6+ eventually, and a
separate kernel for all ARMv4/v5 ones.
If the reasoning has changed, please try to explain the full
situation. On a related topic, what happened to the idea that
ARMv6+ is broken without CMA? I noticed that it's optional
now.
Arnd
next prev parent reply other threads:[~2012-08-20 20:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-20 6:16 [PATCH] ARM: relax conditions required for enabling Contiguous Memory Allocator Marek Szyprowski
2012-08-20 11:29 ` Prabhakar Lad
2012-08-20 20:01 ` Arnd Bergmann [this message]
2012-08-21 12:12 ` Russell King - ARM Linux
2012-08-21 14:47 ` Marek Szyprowski
2012-08-21 14:46 ` Marek Szyprowski
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