On Tue, Sep 18, 2012 at 12:34 PM, Thierry Reding <thierry.red...@avionic-design.de> wrote: > On Tue, Sep 18, 2012 at 11:21:21AM -0600, Bjorn Helgaas wrote: >> On Fri, Sep 14, 2012 at 3:11 PM, Thierry Reding >> <thierry.red...@avionic-design.de> wrote: >> > In order to allow drivers to specify private data for each controller, >> > this commit adds a private_data field to the struct hw_pci. This field >> > is an array of nr_controllers pointers that will be used to initialize >> > the private_data field of the corresponding controller's pci_sys_data >> > structure. >> >> I guess you aren't changing the design here because struct hw_pci >> already includes "nr_controllers," but having nr_controllers and a >> private_data[] array sounds like something that might make it hard to >> hot-add a host bridge after boot. > > What I do in the Tegra PCIe driver is to pass each of the root ports to > pci_common_init() individually because they can be enabled or disabled > by device tree data. I suppose to some degree you can consider that hot- > adding. Not that Tegra is likely to ever need to support that. I don't > know how likely it is for any ARM platform to ever need support for hot- > adding a host bridge. > > Eventually I think it would be advantageous for this to be generalized > further such that PCI initialization can be shared across architectures. > That's probably not an easy task so I was going to start by making > incremental changes that enable the Tegra code to work and, if time > allows, help further with subsequent improvements. > > It also seems that parts of the PCI core aren't ready yet for hot-adding > host bridges. One thing I came across while working on the Tegra code is > that MSI setup and teardown needs to be done by the arch_setup_msi_irq() > and arch_teardown_msi_irq() respectively, which are expected to be > builtin. That was also the last issue that keeps the Tegra PCIe driver > from being built as a module. I think that will also make it impossible > to hot-add host bridges. On x86 this seems to be handled by platform > code, but on Tegra for example MSI setup and teardown is tightly coupled > to the PCIe controller. That was one of the things I thought I could > take a look at eventually, but getting Tegra support cleaned up is > higher priority right now.
The PCI core doesn't support hot-add of host bridges yet, but there's a lot of work in that area right now, which is why it's on my mind :) I'm not suggesting you change anything here; just keep it in the back of your mind for the future. Thanks for the arch_setup_msi_irq() tip; I'll look into that. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
