Messages in this thread |  | | Date | Thu, 20 Mar 2014 16:36:52 +0100 | From | Ben Dooks <> | Subject | Re: DMABOUNCE in pci-rcar |
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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@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?
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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