Re: [PATCH v7 06/17] ARM64 / ACPI: Make PCI optional for ACPI on ARM64

[Hanjun Guo]

On 2015å01æ19æ 18:42, Catalin Marinas wrote:
> On Sun, Jan 18, 2015 at 06:25:53AM +0000, Hanjun Guo wrote:
> > On 2015å01æ16æ 17:49, Catalin Marinas wrote:
> > > On Wed, Jan 14, 2015 at 03:04:54PM +0000, Hanjun Guo wrote:
> > > > --- a/arch/arm64/kernel/pci.c
> > > > +++ b/arch/arm64/kernel/pci.c
> > > > @@ -10,6 +10,7 @@
> > > >     *
> > > >     */
> > > >
> > > > +#include <linux/acpi.h>
> > > >    #include <linux/init.h>
> > > >    #include <linux/io.h>
> > > >    #include <linux/kernel.h>
> > > > @@ -68,3 +69,30 @@ void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
> > > >    	bus->domain_nr = domain;
> > > >    }
> > > >    #endif
> > > > +
> > > > +/*
> > > > + * raw_pci_read/write - Platform-specific PCI config space access.
> > > > + *
> > > > + * Default empty implementation.  Replace with an architecture-specific setup
> > > > + * routine, if necessary.
> > > > + */
> > > > +int raw_pci_read(unsigned int domain, unsigned int bus,
> > > > +		  unsigned int devfn, int reg, int len, u32 *val)
> > > > +{
> > > > +	return -EINVAL;
> > > > +}
> > > > +
> > > > +int raw_pci_write(unsigned int domain, unsigned int bus,
> > > > +		unsigned int devfn, int reg, int len, u32 val)
> > > > +{
> > > > +	return -EINVAL;
> > > > +}
> > > > +
> > > > +#ifdef CONFIG_ACPI
> > > > +/* Root bridge scanning */
> > > > +struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> > > > +{
> > > > +	/* TODO: Should be revisited when implementing PCI on ACPI */
> > > > +	return NULL;
> > > > +}
> > > > +#endif
> [...]
> > > When PCI is enabled and the above functions are compiled in, do they
> > > need to return any useful data or just -EINVAL. Are they ever called?
> >
> > They will be called if PCI root bridge is defined in DSDT, should I
> > print some warning message before it is implemented?
>
> My point: do they need to return real data when a PCI root bridge is
> defined in DSDT or you always expect them to always return some -E*? Can
> you explain why?

Not always return -E* or NULL;

For raw_pci_read/write(), they are needed to access the PCI config space
before the PCI root bus is created. so they will return 0 if access to
PCI config space is ok; pci_acpi_scan_root() will return root bus
pointer if it is successfully created.

Thanks
Hanjun
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