Messages in this thread | | | Date | Thu, 20 Mar 2014 18:25:25 +0100 | From | Ben Dooks <> | Subject | Re: DMABOUNCE in pci-rcar |
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On 20/03/14 17:41, Arnd Bergmann wrote: > On Thursday 20 March 2014 17:12:43 Ben Dooks wrote: >> On 20/03/14 17:09, Arnd Bergmann wrote: >>> On Thursday 20 March 2014 16:04:36 Ben Dooks wrote: > >>>> 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. >>> >>> Did it work before these patches got applied initially? >> >> It did, but I cannot remember if we where limiting DRAM to 1GiB >> or not. > > I would assume you did, or you happened to never actually use > memory higher than that for DMA during tests. > >>>> 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? >>> >>> You can solve the case for dma_alloc_coherent() this way, or by >>> setting the mask correctly. It won't help you for dma_map_* though, >>> which still requires someone to add support for swiotlb or using >>> an IOMMU if present. >> >> We do not have an IOMMU present at the moment. Not sure how >> to go about setting a mask on a pci-probed device. > > Ah, right. The mask is a problem because PCI devices assume that > they can do DMA to any 32-bit masked address without calling > dma_set_mask. Your trick to describe the system memory at a different > physical alias would solve this part. Another option might be to > add a quirk in the OHCI/EHCI drivers, if you are able to detect > this special case from the PCI IDs. Whether we can allow the PCI host > controller to just set a mask is an open question. If we decide to go > that route, you should be able to do it using the add_bus() callback > in the host controller driver. However, it would be a departure from > the normal way of doing PCI DMA, and I can't foresee what the implications > would be.
So doing:
static void pci_rcar_fixup(struct pci_dev *dev) { if (dev->bus->ops == &rcar_pci_ops) { dev_info(&dev->dev, "applying new dma mask\n"); dev->dma_mask = DMA_BIT_MASK(31); } }
DECLARE_PCI_FIXUP_EARLY(PCI_ANY_ID, PCI_ANY_ID, pci_rcar_fixup);
Did not work for me :(
-- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius
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