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. > 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. Thanks Phil -- 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
