(sorry for replying to a months old thread) On Mon, Apr 07, 2014 at 06:58:24PM +0100, Bjorn Helgaas wrote: > On Mon, Apr 7, 2014 at 5:36 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > > I think migrating other architectures to use the same code should be > > a separate effort from adding a generic implementation that can be > > used by arm64. It's probably a good idea to have patches to convert > > arm32 and/or microblaze. > > Let me reiterate that I am 100% in favor of replacing arch-specific > code with more generic implementations. > > However, I am not 100% in favor of doing it as separate efforts > (although maybe I could be convinced). The reasons I hesitate are > that (1) if only one architecture uses a new "generic" implementation, > we really don't know whether it is generic enough, (2) until I see the > patches to convert other architectures, I have to assume that I'm the > one who will write them, and (3) as soon as we add the code to > drivers/pci, it becomes partly my headache to maintain it, even if > only one arch benefits from it. I agree and understand your point. > Please don't think I'm questioning anyone's intent or good will. It's > just that I understand the business pressures, and I know how hard it > can be to justify this sort of work to one's management, especially > after the immediate problem has been solved. But, unfortunately, that's something we failed to address in reasonable time (even though I was one of the proponents of the generic PCIe implementation). This work is very likely to slip further into the late part of this year and I am aware that several ARM partners are blocked on the (upstream) availability of PCIe support for the arm64 kernel. Although a bit late, I'm raising this now and hopefully we'll come to a conclusion soon. Delaying arm64 PCIe support even further is not a real option, which leaves us with: 1. Someone else (with enough PCIe knowledge) volunteering to take over soon or 2. Dropping Liviu's work and going for an arm64-specific implementation (most likely based on the arm32 implementation, see below) First option is ideal but there is work to do as laid out by Arnd here: http://article.gmane.org/gmane.linux.kernel/1679304 The latest patches from Liviu are here (they only target arm64 and there are additional comments to be addressed from the above thread): http://linux-arm.org/git?p=linux-ld.git;a=shortlog;h=refs/heads/for-upstream/pci-next The main reason for the second option is timing. We could temporarily move Liviu's code under arch/arm64 with the hope that we generalise it later. However, the risk is even higher that once the code is in mainline, the generic implementation won't happen. In which case, I don't see much point in departing from the arm32 PCI API, making bios32 clone the best second option. For the alternative implementation above, we already have a heavily cut down version of the arm32 PCI support but only tested in a virtual environment so far: https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/log/?h=pci/bios32 In conclusion, unless someone volunteers for the first option fairly soon, we'll post the alternative patches for review and take it from there. Thanks. -- Catalin -- 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
