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

[Rob Herring]

On Tue, Sep 23, 2014 at 2:01 PM, Liviu Dudau <Liviu.Dudau@xxxxxxx> 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@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Grant Likely <grant.likely@xxxxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Signed-off-by: Liviu Dudau <Liviu.Dudau@xxxxxxx>

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.

> +       if (!value || len < sizeof(*value))
> +               return -EINVAL;
> +
> +       domain = (u16)be32_to_cpup(value);

of_property_read_u32 would not work here?

> +
> +       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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