Re: [PATCH] arm64: make CONFIG_ZONE_DMA user settable

[Catalin Marinas <catalin.marinas@arm.com>]

On Fri, Jul 18, 2014 at 12:58:31PM +0100, Anup Patel wrote:
> On 18 July 2014 16:37, Catalin Marinas <catalin.marinas@arm.com> wrote:
> > From 133656f8378dbb838ad5f12ea29aa9303d7ca922 Mon Sep 17 00:00:00 2001
> > From: Catalin Marinas <catalin.marinas@arm.com>
> > Date: Fri, 18 Jul 2014 11:54:37 +0100
> > Subject: [PATCH] arm64: Create non-empty ZONE_DMA when DRAM starts above 4GB
> >
> > ZONE_DMA is created to allow 32-bit only devices to access memory in the
> > absence of an IOMMU. On systems where the memory starts above 4GB, it is
> > expected that some devices have a DMA offset hardwired to be able to
> > access the bottom of the memory. Linux currently supports DT bindings
> > for the DMA offsets but they are not (easily) available early during
> > boot.
> >
> > This patch tries to guess a DMA offset and assumes that ZONE_DMA
> > corresponds to the 32-bit mask above the start of DRAM.
> >
> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Mark Salter <msalter@redhat.com>
[...]
> Linux-3.16-rcX is broken on X-Gene Mustang because
> on X-Gene Mustang the DRAM starts at 0x4000000000.
> 
> I have tested your patch and the original patch from
> this thread. Both patches fixes the issue for X-Gene
> Mustang and Linux-3.16-rc5 happily boots on X-Gene.
> 
> Can you to send your patch as Linux-3.16-rcX fix?

It needs some more testing and if there is time, yes, otherwise it will
just be cc stable.

> For your patch, you can have:
> Tested-by: Anup Patel <anup.patel@linaro.org>

Thanks.

-- 
Catalin