DMABOUNCE in pci-rcar

[Russell King - ARM Linux]

On Thu, Mar 20, 2014 at 04:04:36PM +0100, Ben Dooks wrote:
> On 26/02/14 20:57, Arnd Bergmann wrote:
>> On Wednesday 26 February 2014 12:48:17 Bjorn Helgaas wrote:
>>> On Mon, Feb 24, 2014 at 4:00 AM, Arnd Bergmann <arnd at arndb.de> wrote:
>>>> Hi Magnus,
>>>>
>>>> I noticed during randconfig testing that you enabled DMABOUNCE for the
>>>> pci-rcar-gen2 driver as posted in this patch https://lkml.org/lkml/2014/2/5/30
>>>>
>>>> I didn't see the original post unfortunately, but I fear we have to
>>>> revert it and come up with a better solution, ...
>>>
>>> Sounds like I should drop the following patches from my pci/host-rcar
>>> branch for now?
>>>
>>>    PCI: rcar: Add DMABOUNCE support
>>>    PCI: rcar: Enable BOUNCE in case of HIGHMEM
>>>    PCI: rcar: Make the Kconfig dependencies more generic
>>
>> Sounds good to me. The last patch is actually fine, but you'll have to
>> fix the context to apply it without the other two.
>
> As a note, if we now boot a Lager with DT on 3.14-rc3 series the USB
> controllers no longer work with full 2GiB RAM enabled in the device
> tree.
>
> Could we work around this by having 1GiB of memory defined in the
> 32bit memory and then add the rest of the 3GiB from the >32bit
> area via LPAE? Will the kernel ever try to allocate DMA memory from
> anything >32bit?

Ignore highmem.  What is the actual hardware restriction concerning memory
it can access?

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