Re: [PATCH V9 11/11] ARM64/PCI: Support for ACPI based PCI host controller

[Tomasz Nowicki]

On 23.11.2016 19:22, Bjorn Helgaas wrote:
> On Wed, Nov 23, 2016 at 12:21:03PM +0100, Tomasz Nowicki wrote:
> > Hi Bjorn,
> >
> > On 23.11.2016 00:13, Bjorn Helgaas wrote:
> > > Hi Tomasz,
> > >
> > > On Fri, Jun 10, 2016 at 09:55:19PM +0200, Tomasz Nowicki wrote:
> > > > Implement pci_acpi_scan_root and other arch-specific call so that ARM64
> > > > can start using ACPI to setup and enumerate PCI buses.
> > > >
> > > > Prior to buses enumeration the pci_acpi_scan_root() implementation looks
> > > > for configuration space start address (obtained through ACPI _CBA method or
> > > > MCFG interface). If succeed, it uses ECAM library to create new mapping.
> > > > Then it attaches generic ECAM ops (pci_generic_ecam_ops) which are used
> > > > for accessing configuration space later on.
> > > > ...
> > >
> > > > +static struct acpi_pci_root_ops acpi_pci_root_ops = {
> > > > +	.release_info = pci_acpi_generic_release_info,
> > > > +};
> > > > +
> > > > +/* Interface called from ACPI code to setup PCI host controller */
> > > > struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> > > > {
> > > > -	/* TODO: Should be revisited when implementing PCI on ACPI */
> > > > -	return NULL;
> > > > +	int node = acpi_get_node(root->device->handle);
> > > > +	struct acpi_pci_generic_root_info *ri;
> > > > +	struct pci_bus *bus, *child;
> > > > +
> > > > +	ri = kzalloc_node(sizeof(*ri), GFP_KERNEL, node);
> > > > +	if (!ri)
> > > > +		return NULL;
> > > > +
> > > > +	ri->cfg = pci_acpi_setup_ecam_mapping(root);
> > > > +	if (!ri->cfg) {
> > > > +		kfree(ri);
> > > > +		return NULL;
> > > > +	}
> > > > +
> > > > +	acpi_pci_root_ops.pci_ops = &ri->cfg->ops->pci_ops;
> > >
> > > This has already been merged, but this isn't right, is it?  We're
> > > writing a host controller-specific pointer into the single system-wide
> > > acpi_pci_root_ops, then passing it on to acpi_pci_root_create().
> > >
> > > Today, I think ri->cfg->ops->pci_ops is always &pci_generic_ecam_ops,
> > >from this path:
> > >  ri->cfg = pci_acpi_setup_ecam_mapping
> > >    cfg = pci_ecam_create(..., &pci_generic_ecam_ops)
> > >      cfg = kzalloc(...)
> > >      cfg->ops = ops             # &pci_generic_ecam_ops
> > >
> > > But we're about to merge the ECAM quirks series, which will mean it
> > > may not be &pci_generic_ecam_ops.  Even apart from the ECAM quirks, we
> > > should avoid this pattern of putting device-specific info in a single
> > > shared structure because it's too difficult to verify that it's
> > > correct.
> >
> > Well spotted. I agree, we need to fix this. How about this:
> > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> > index fb439c7..31c0e1c 100644
> > --- a/arch/arm64/kernel/pci.c
> > +++ b/arch/arm64/kernel/pci.c
> > @@ -152,33 +152,35 @@ static void
> > pci_acpi_generic_release_info(struct acpi_pci_root_info *ci)
> >
> >         ri = container_of(ci, struct acpi_pci_generic_root_info, common);
> >         pci_ecam_free(ri->cfg);
> > +       kfree(ci->ops);
> >         kfree(ri);
> >  }
> >
> > -static struct acpi_pci_root_ops acpi_pci_root_ops = {
> > -       .release_info = pci_acpi_generic_release_info,
> > -};
> > -
> >  /* Interface called from ACPI code to setup PCI host controller */
> >  struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> >  {
> >         int node = acpi_get_node(root->device->handle);
> >         struct acpi_pci_generic_root_info *ri;
> >         struct pci_bus *bus, *child;
> > +       struct acpi_pci_root_ops *root_ops;
> >
> >         ri = kzalloc_node(sizeof(*ri), GFP_KERNEL, node);
> >         if (!ri)
> >                 return NULL;
> >
> > +       root_ops = kzalloc_node(sizeof(*root_ops), GFP_KERNEL, node);
> > +       if (!root_ops)
> > +               return NULL;
> > +
> >         ri->cfg = pci_acpi_setup_ecam_mapping(root);
> >         if (!ri->cfg) {
> >                 kfree(ri);
> > +               kfree(root_ops);
> >                 return NULL;
> >         }
> >
> > -       acpi_pci_root_ops.pci_ops = &ri->cfg->ops->pci_ops;
> > -       bus = acpi_pci_root_create(root, &acpi_pci_root_ops, &ri->common,
> > -                                  ri->cfg);
> > +       root_ops->release_info = pci_acpi_generic_release_info;
> > +       root_ops->pci_ops = &ri->cfg->ops->pci_ops;
> > +       bus = acpi_pci_root_create(root, root_ops, &ri->common, ri->cfg);
> >         if (!bus)
> >                 return NULL;
> >
> > Of course, this should be the part of ECAM quirks core patches.
> >
> > The other option we have is to remove "struct pci_ops *pci_ops;"
> > from acpi_pci_root_ops structure and pass struct pci_ops as an extra
> > argument to acpi_pci_root_create(). What do you think?
>
> I think your patch above is fine and avoids the need to change the x86 and
> ia64 code.  Would you mind packaging this up with a changelog and
> signed-off-by?  I can take care of putting it in the ECAM series.

Sure, I have just sent the patch in replay to ECAM quirks V6 patch set.

Let us know when you update your branch so we base our quirks on it.

Thanks,
Tomasz