On Sat, Feb 15, 2014 at 02:03:26PM +0100, Arnd Bergmann wrote: > On Friday 14 February 2014 22:00:47 Liviu Dudau wrote: > > > > What I'm going to suggest in my v2 patch (hope to send it before Monday) > > is a new API in the generic PCI code that will allow you to create a > > host bridge in a new domain or in the existing domain, with the management > > of the domain number being done in the generic code. > > > > Something like: > > > > int create_hostbridge_in_new_domain(....); > > int create_hostbridge(....); > > > > with the functions being wrappers around the pci_hostbridge_of_init function > > that I'm introducing. > > > > What do you think? > > Not sure. It would still keep the decision about whether to use a > new domain or not in the host bridge driver, but that doesn't seem > like the right place. The same driver might be used in different > ways based on what is around it. > > I've also had a look at the MIPS implementation now, which has its > own way of dealing with this, see arch/mips/pci/pci.c. > > There was also an interesting comment in the MIPS header file: > > /* For compatibility with current (as of July 2003) pciutils > and XFree86. Eventually will be removed. */ > unsigned int need_domain_info; > > This is over ten years old, so I wonder if we can start assuming that > domains work out of the box now. All references to problems from > PCI domains are about old code (ca. pre-2007) that doesn't understand > nonzero domains and that has since been fixed. I am pretty sure we > don't need to ever worry about stuffing multiple host bridges into > a domain other than the first one, and I also doubt we have to worry > about the problem at all on arm64 as we won't run old binaries on it > (or arm32 compat mode binaries that need to manage PCI devices). > > Can anyone with more experience on the subject than me (Bjorn, > Russell, Jason, ...) think of a reason why we would not want to > just use a new domain for every host bridge we find? With ACPI on x86 and ia64, we currently use _SEG directly as the Linux PCI domain. Are you proposing that we make the Linux PCI domain independent of _SEG? It will look sort of funny to have things like this: ACPI: PCI Root Bridge [L000] (_SEG 0 domain 0000 [bus 00-1b]) ACPI: PCI Root Bridge [L001] (_SEG 0 domain 0001 [bus 1c-37]) ACPI: PCI Root Bridge [L002] (_SEG 0 domain 0002 [bus 38-53]) where the firmware had _SEG==0 for all the bridges and assigned non-overlapping bus number ranges, but since nothing in PCI really depends on the domain, I guess it should work. Bjorn -- 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
