Re: [PATCH 00/11] ARM: PrimeCell DMA Interface v5

[Dan Williams]

On Sat, May 1, 2010 at 3:44 PM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> On Sat, May 01, 2010 at 03:00:09PM -0700, Dan Williams wrote:
>> Just to clarify are you nak'ing these patches for upstream inclusion
>> until this testing occurs?  Or do we just need a !ARCH_VERSATILE
>> somewhere to allow any incompatibilities to be worked out later
>> in-tree?
>
> What I don't want to do is to get into the situation where we throw
> this patchset into the kernel and then find that we have to invent a
> whole new implementation in the various primecell drivers to support
> the Versatile hardware.
>
> Versatile has some MUXing on three of the DMA signals, so (eg) we
> really don't want UARTs claiming DMAs just because they're in existence
> and not in use - that would prevent DMAs from being used for (eg) AACI
> or MMC.
>
> The alternative is that we could just take the attitude that Versatile/
> Realview will never have DMA support implemented, but that seems rather
> silly, as they've tended to be the first platforms I get new CPU
> architectures for.  (This is why DMA coherency stuff on new architectures
> tends to be left for others to do...)

Ok, it will be good to have this approach vetted on a challenging
arch.  We'll see where things stand when the merge window opens.

--
Dan
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