Hi Olav, On Fri, Jun 27, 2014 at 11:23:27PM +0100, Olav Haugan wrote: > On 6/25/2014 2:18 AM, Will Deacon wrote: > > Why can't it be dynamically detected? Whilst the StreamIDs are fixed in > > hardware (from the SMMU architecture perspective), the SMRs are completely > > programmable. Why doesn't something like Andreas's proposal work for you? > > The idea there was to find the constant bits among the StreamIDs for a > > master and create the mask accordingly. > > > Lets say I have an IOMMU with 2 masters and 2 SMRn slots with the > following stream IDs coming from the masters: > > Master 1: 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28 > Master 2: 0x30 > > To make this work I would program SMR[0] with StreamID 0x20 and mask 0xF > to ignore lower 4 bits. SMR[1] would just be StreamID 0x30 with mask 0x0. > > However, I could also have an IOMMU with 2 masters and 9 SMRn slots with > the following stream IDs: > > Master 1: 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28 > Master 2: 0x29 > > Here I would program all SMRn and leave the mask to be 0 for all SMRn's. > So how do I detect when to apply a mask or not? You would aim to use the smallest number of SMRs per master possible. You could probably use: Master 1: SMR[0].id == 0x20, SMR[0].mask = 0x07 SMR[1].id == 0x28, SMR[1].mask = 0x00 Master 2: SMR[2].id == 0x29, SMR[2].mask = 0x00 > I am not familiar with Andreas's proposal. Do you have a link? http://marc.info/?l=linux-arm-kernel&m=139110598005846&w=2 Note that since Calxeda went under, Andreas is unfortunately no longer working on this. Will -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html