Re: [PATCH v12 08/12] PCI: OF: Introduce helper function for retrieving PCI domain numbers

[liviu@dudau.co.uk]

On Fri, Sep 26, 2014 at 01:20:39PM -0500, Rob Herring wrote:
> On Tue, Sep 23, 2014 at 2:01 PM, Liviu Dudau <Liviu.Dudau@arm.com> wrote:
> > Add pci_get_new_domain_nr() to allocate a new domain number
> > and of_get_pci_domain_nr() to retrieve the PCI domain number
> > of a given device from DT. Host bridge drivers or architecture
> > specific code can choose to implement their PCI domain number
> > policy using these two functions.
> >
> > Using of_get_pci_domain_nr() guarantees a stable PCI domain
> > number on every boot provided that all host bridge controllers
> > are assigned a number in the device tree using "linux,pci-domain"
> > property. Mix use of pci_get_new_domain_nr() and of_get_pci_domain_nr()
> > is not recommended as it can lead to potentially conflicting
> > domain numbers being assigned to root busses behind different
> > host bridges.
> >
> > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Grant Likely <grant.likely@linaro.org>
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
> 
> Looks pretty good, but a couple of comments that can be addressed as
> follow-up patches.
> 
> > ---
> >  drivers/of/of_pci.c    | 25 +++++++++++++++++++++++++
> >  drivers/pci/pci.c      |  9 +++++++++
> >  include/linux/of_pci.h |  7 +++++++
> >  include/linux/pci.h    |  3 +++
> >  4 files changed, 44 insertions(+)
> >
> > diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> > index 8481996..82d172f 100644
> > --- a/drivers/of/of_pci.c
> > +++ b/drivers/of/of_pci.c
> > @@ -89,6 +89,31 @@ int of_pci_parse_bus_range(struct device_node *node, struct resource *res)
> >  }
> >  EXPORT_SYMBOL_GPL(of_pci_parse_bus_range);
> >
> > +/**
> > + * This function will try to obtain the host bridge domain number by
> > + * finding a property called "linux,pci-domain" of the given device node.
> > + *
> > + * @node: device tree node with the domain information
> > + *
> > + * Returns the associated domain number from DT in the range [0-0xffff], or
> > + * a negative value if the required property is not found.
> > + */
> > +int of_get_pci_domain_nr(struct device_node *node)
> > +{
> > +       const __be32 *value;
> > +       int len;
> > +       u16 domain;
> > +
> > +       value = of_get_property(node, "linux,pci-domain", &len);
> 
> This needs to be documented.

I would say needs agreed on *and* documented.

> 
> > +       if (!value || len < sizeof(*value))
> > +               return -EINVAL;
> > +
> > +       domain = (u16)be32_to_cpup(value);
> 
> of_property_read_u32 would not work here?

It should, I guess, but I want to limit the domain number range to 16 bits.

Best regards,
Liviu

> 
> > +
> > +       return domain;
> > +}
> > +EXPORT_SYMBOL_GPL(of_get_pci_domain_nr);
> > +
> >  #ifdef CONFIG_PCI_MSI
> >
> >  static LIST_HEAD(of_pci_msi_chip_list);
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 2c9ac70..d36f35f 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -4406,6 +4406,15 @@ static void pci_no_domains(void)
> >  #endif
> >  }
> >
> > +#ifdef CONFIG_PCI_DOMAINS
> > +static atomic_t __domain_nr = ATOMIC_INIT(-1);
> > +
> > +int pci_get_new_domain_nr(void)
> > +{
> > +       return atomic_inc_return(&__domain_nr);
> > +}
> > +#endif
> > +
> >  /**
> >   * pci_ext_cfg_avail - can we access extended PCI config space?
> >   *
> > diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
> > index dde3a4a..71062e9 100644
> > --- a/include/linux/of_pci.h
> > +++ b/include/linux/of_pci.h
> > @@ -15,6 +15,7 @@ struct device_node *of_pci_find_child_device(struct device_node *parent,
> >  int of_pci_get_devfn(struct device_node *np);
> >  int of_irq_parse_and_map_pci(const struct pci_dev *dev, u8 slot, u8 pin);
> >  int of_pci_parse_bus_range(struct device_node *node, struct resource *res);
> > +int of_get_pci_domain_nr(struct device_node *node);
> >  #else
> >  static inline int of_irq_parse_pci(const struct pci_dev *pdev, struct of_phandle_args *out_irq)
> >  {
> > @@ -43,6 +44,12 @@ of_pci_parse_bus_range(struct device_node *node, struct resource *res)
> >  {
> >         return -EINVAL;
> >  }
> > +
> > +static inline int
> > +of_get_pci_domain_nr(struct device_node *node)
> > +{
> > +       return -1;
> > +}
> >  #endif
> >
> >  #if defined(CONFIG_OF) && defined(CONFIG_PCI_MSI)
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index a494e5d..150da2d 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1285,10 +1285,12 @@ void pci_cfg_access_unlock(struct pci_dev *dev);
> >   */
> >  #ifdef CONFIG_PCI_DOMAINS
> >  extern int pci_domains_supported;
> > +int pci_get_new_domain_nr(void);
> >  #else
> >  enum { pci_domains_supported = 0 };
> >  static inline int pci_domain_nr(struct pci_bus *bus) { return 0; }
> >  static inline int pci_proc_domain(struct pci_bus *bus) { return 0; }
> > +static inline int pci_get_new_domain_nr(void) { return -ENOSYS; }
> >  #endif /* CONFIG_PCI_DOMAINS */
> >
> >  /*
> > @@ -1417,6 +1419,7 @@ static inline struct pci_dev *pci_get_bus_and_slot(unsigned int bus,
> >
> >  static inline int pci_domain_nr(struct pci_bus *bus) { return 0; }
> >  static inline struct pci_dev *pci_dev_get(struct pci_dev *dev) { return NULL; }
> > +static inline int pci_get_new_domain_nr(void) { return -ENOSYS; }
> >
> >  #define dev_is_pci(d) (false)
> >  #define dev_is_pf(d) (false)
> > --
> > 2.1.0
> >
> --
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