[RFC v5 1/8] PCI: Introduce domain_nr in pci_host_bridge

[Boqun Feng]

On Tue, Jul 20, 2021 at 05:49:25PM -0500, Bjorn Helgaas wrote:
> On Tue, Jul 20, 2021 at 09:44:22PM +0800, Boqun Feng wrote:
> > Currently we retrieve the PCI domain number of the host bridge from the
> > bus sysdata (or pci_config_window if PCI_DOMAINS_GENERIC=y). Actually
> > we have the information at PCI host bridge probing time, and it makes
> > sense that we store it into pci_host_bridge. One benefit of doing so is
> > the requirement for supporting PCI on Hyper-V for ARM64, because the
> > host bridge of Hyper-V doesn't have pci_config_window, whereas ARM64 is
> > a PCI_DOMAINS_GENERIC=y arch, so we cannot retrieve the PCI domain
> > number from pci_config_window on ARM64 Hyper-V guest.
> > 
> > As the preparation for ARM64 Hyper-V PCI support, we introduce the
> > domain_nr in pci_host_bridge and a sentinel value to allow drivers to
> > set domain numbers properly at probing time. Currently
> > CONFIG_PCI_DOMAINS_GENERIC=y archs are only users of this
> > newly-introduced field.
> > 
> > Signed-off-by: Boqun Feng <boqun.feng at gmail.com>
> 
> Once all the issues are ironed out, Lorenzo should probably merge this
> since it's primarily Hyper-V stuff, but I'm OK with this part:
> 
> Acked-by: Bjorn Helgaas <bhelgaas at google.com>
> 

Thanks!

> But fix the comment issue below.
> 

Just send a v5.1 for this patch with the comment fixed and your
Acked-by.

Regards,
Boqun

> > ---
> >  drivers/pci/probe.c |  6 +++++-
> >  include/linux/pci.h | 10 ++++++++++
> >  2 files changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 79177ac37880..60c50d4f156f 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -594,6 +594,7 @@ static void pci_init_host_bridge(struct pci_host_bridge *bridge)
> >  	bridge->native_pme = 1;
> >  	bridge->native_ltr = 1;
> >  	bridge->native_dpc = 1;
> > +	bridge->domain_nr = PCI_DOMAIN_NR_NOT_SET;
> >  
> >  	device_initialize(&bridge->dev);
> >  }
> > @@ -898,7 +899,10 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
> >  	bus->ops = bridge->ops;
> >  	bus->number = bus->busn_res.start = bridge->busnr;
> >  #ifdef CONFIG_PCI_DOMAINS_GENERIC
> > -	bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
> > +	if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
> > +		bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
> > +	else
> > +		bus->domain_nr = bridge->domain_nr;
> >  #endif
> >  
> >  	b = pci_find_bus(pci_domain_nr(bus), bridge->busnr);
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 540b377ca8f6..2c413a64d168 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -526,6 +526,15 @@ static inline int pci_channel_offline(struct pci_dev *pdev)
> >  	return (pdev->error_state != pci_channel_io_normal);
> >  }
> >  
> > +/*
> > +* Currently in ACPI spec, for each PCI host bridge, PCI Segment Group number is
> > +* limited to a 16-bit value, therefore (int)-1 is not a valid PCI domain number,
> > +* and can be used as a sentinel value indicating >domain_nr is not set by the
> > +* driver (and CONFIG_PCI_DOMAINS_GENERIC=y archs will set it with
> > +* pci_bus_find_domain_nr()).
> > +*/
> 
> Fix comment indentation (follow style of other comments in this file).
> 
> s/>domain_nr/->domain_nr/
> 
> > +#define PCI_DOMAIN_NR_NOT_SET (-1)
> > +
> >  struct pci_host_bridge {
> >  	struct device	dev;
> >  	struct pci_bus	*bus;		/* Root bus */
> > @@ -533,6 +542,7 @@ struct pci_host_bridge {
> >  	struct pci_ops	*child_ops;
> >  	void		*sysdata;
> >  	int		busnr;
> > +	int		domain_nr;
> >  	struct list_head windows;	/* resource_entry */
> >  	struct list_head dma_ranges;	/* dma ranges resource list */
> >  	u8 (*swizzle_irq)(struct pci_dev *, u8 *); /* Platform IRQ swizzler */
> > -- 
> > 2.30.2
> >