On 20/09/16 16:03, Magnus Damm wrote: > Hi Robin, > > Thanks for your feedback!! > > On Tue, Sep 20, 2016 at 10:18 PM, Robin Murphy <robin.murphy@xxxxxxx> wrote: >> Hi Magnus, >> >> On 20/09/16 13:41, Magnus Damm wrote: >>> From: Magnus Damm <damm+renesas@xxxxxxxxxxxxx> >>> >>> Update the IPMMU driver to return -ENODEV when adding devices >>> not hooked up a particular IPMMU instance. >>> >>> Currently the ->add_device() callback implementation in the IPMMU >>> driver returns -ENODEV for devices with no "iommus" property, >>> however the function ipmmu_find_utlbs() may return -EINVAL. >> >> If there were no "iommus" property at all, of_parse_phandle_with_args() >> should return -ENOENT - that probably does want to be caught and passed >> back as -ENODEV to imply an untranslated device. On the other hand, >> -EINVAL would stem from the existence of the property, but in a somehow >> erroneous manner - other than the "args.np != mmu->dev->of_node" check >> (which could legitimately fail and be safely ignored if there are >> multiple IOMMUs in the system), any other reason implies a DT error >> which probably shouldn't be papered over. > > Regarding -ENOENT to -ENODEV, I agree but I believe this case is > already handled. The ->add_device() callback seems to be using > of_count_phandle_with_args() to check for the presence of "iommus" > property before calling ipmmu_find_utlbs(). So for the case with no > "iommus" property at all it is returned as -ENODEV as you suggest. Ah, right you are, I missed that there was a separate check earlier. > The ->add_device() callback has the ret variable initialised to > -ENODEV by default. In case there is only one IPMMU device on the > ipmmu_device list and it matches the struct device passed to the > ipmmu_add_device() function then all is fine. However when there are > more than one IPMMU device on the ipmmu_device list then > ipmmu_find_utlbs() may return -EINVAL. Judging by the code this seems > to happen when the order of the IPMMU devices on the "iommus" property > does not match the IPMMU order on the ipmmu_device list. > > Hm, I wonder if all this should be replaced with ->xlate() somehow? Ideally, yes - the core code already has most of this covered, so taking advantage of it would be good. I think the only slight hiccup is that the 32-bit DMA code is then going to call attach_dev() with a domain you probably don't want, before you get your add_device() call. Other than handling that vs. group-based default domains for 64-bit, though, there shouldn't be anything else to special-case, I don't think. I'm finally starting to have a look into converting the arch/arm code over to use groups and default domains sensibly, but I suspect that's ultimately going to have some dependency on the probe deferral stuff, rather than introduce the same bus notifier bodge we currently have on arm64. Robin. > > Thanks, > > / magnus >
