Re: DMABOUNCE in pci-rcar
From: Ben Dooks
Date: Thu Mar 20 2014 - 11:37:28 EST
On 20/03/14 16:26, Russell King - ARM Linux wrote:
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@xxxxxxxx> 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?
If the window is set to 2GiB it can only access 2GiB aligned to 2GiB
boundary, however DRAM spans a 2GiB boundary (being at 1-3GiB)
--
Ben Dooks http://www.codethink.co.uk/
Senior Engineer Codethink - Providing Genius
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