Re: [PATCH 1/1] powerpc/64: Adjust order in pcibios_init()

[Oliver <oohall@gmail.com>]

On Fri, Feb 22, 2019 at 2:24 PM Sam Bobroff <sbobroff@linux.ibm.com> wrote:
>
> Hey all,
>
> After some consideration, I've decided to post a v2 of this patch that
> will make it a bit safer (although I haven't seen any problems with it)
> and make it a little easier to refactor some of the EEH code that
> interacts with the hooks.

Can you be a little more specific?

> Cheers,
> Sam.
>
> On Thu, Feb 14, 2019 at 04:14:42PM +1100, Sam Bobroff wrote:
> > The pcibios_init() function for 64 bit PowerPC currently calls
> > pci_bus_add_devices() before pcibios_resource_survey(), which seems
> > incorrect because it adds devices and attempts to bind their drivers
> > before allocating their resources (although no problems seem to be
> > apparent).
> >
> > So move the call to pci_bus_add_devices() to after
> > pcibios_resource_survey().
> >
> > This will also allow the ppc_md.pcibios_bus_add_device() hooks to
> > perform actions that depend on PCI resources, both during rescanning
> > (where this is already the case) and at boot time, which should
> > support improvements and refactoring.
> >
> > Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
> > ---
> > Hi everyone,
> >
> > I've tested this on a P9 for both the host and a KVM guest, and the change
> > hasn't caused any differences in PCI resource assignments or the general boot
> > messages.
> >
> > I've also had a go at inspecting most of the code used by pci_bus_add_devices()
> > and pcibios_resource_survey() and it doesn't look like there are going to be
> > any changes in behaviour caused by reordering.  It might be worth mentioning
> > that the hotplug path (see pcibios_finish_adding_to_bus()) already does
> > resource allocation before calling pci_bus_add_devices().
> >
> > However, it would be great if someone could test this change on some older
> > hardware or comment on wether we should make the same change on 32 bit machines.
> >
> > Cheers,
> > Sam.
> >
> >  arch/powerpc/kernel/pci_64.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
> > index 9d8c10d55407..1ce28888dbdb 100644
> > --- a/arch/powerpc/kernel/pci_64.c
> > +++ b/arch/powerpc/kernel/pci_64.c
> > @@ -58,14 +58,16 @@ static int __init pcibios_init(void)
> >       pci_add_flags(PCI_ENABLE_PROC_DOMAINS | PCI_COMPAT_DOMAIN_0);
> >
> >       /* Scan all of the recorded PCI controllers.  */
> > -     list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
> > +     list_for_each_entry_safe(hose, tmp, &hose_list, list_node)
> >               pcibios_scan_phb(hose);
> > -             pci_bus_add_devices(hose->bus);
> > -     }
> >
> >       /* Call common code to handle resource allocation */
> >       pcibios_resource_survey();
> >
> > +     /* Add devices. */
> > +     list_for_each_entry_safe(hose, tmp, &hose_list, list_node)
> > +             pci_bus_add_devices(hose->bus);
> > +
> >       printk(KERN_DEBUG "PCI: Probing PCI hardware done\n");
> >
> >       return 0;
> > --
> > 2.19.0.2.gcad72f5712
> >