On Wednesday 26 March 2014 09:55:04 Phil.Edworthy@xxxxxxxxxxx wrote: > Hi Arnd, > > On: 25/03/2014 18:42, Arnd wrote: > > Subject: Re: [PATCH v5 6/9] ARM: shmobile: Add PCIe device tree nodes > for R8A7790 > > > > On Tuesday 25 March 2014 16:56:41 Phil Edworthy wrote: > > > + /* Map all possible DDR as inbound ranges */ > > > + dma-ranges = <0x42000000 0 0x40000000 0 0x40000000 0 > 0x80000000 > > > + 0x43000000 1 0x80000000 1 0x80000000 0 > 0x80000000>; > > > > Typo: 0x43000000 should be 0x42000000 I guess. > I used 0x43000000 as this is a 64-bit type. The OF PCI range code > currently treats both 32 and 64-bit types the same way, but I thought it > would be good to set this in case we ever need to use it. Ah, I forgot about the space identifier. It looks correct then, but it seems a little strange to use a 32-bit identifier in one case and a 64-bit one in the other. > > Since you control the mapping, I wonder if you could also do this as > > > > dma-ranges = <0x42000000 0 0x00000000 0 0x40000000 0 > 0x80000000 > > 0x43000000 0 0x80000000 1 0x80000000 0 > 0x80000000>; > > > > i.e. map all the RAM into PCI bus addresses below the 32-bit boundary. > > This would be really nice from the perspective that now all PCI > > devices could access all of RAM without using an IOMMU or the > > relying on 64-bit master capability. > > > > The downside of this is that you'd probably need a custom dma_map_ops > > wrapper. > Since the OF PCi range code treats both 32 and 64-bit types the same way, > my PCIe driver only creates 64-bit mappings. In addition, the PCIe > controller has to use a 64-bit mapping for anything over 2GiB. Based on > this, I think it's sensible to leave the mappings as 1-to-1. I'm not following, sorry. What is the hardware requirement in the controller? Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
