Re: [PATCH v4 4/6] of/pci: add of_pci_dma_configure() update dma configuration

[Bjorn Helgaas <bhelgaas@google.com>]

On Mon, Jan 26, 2015 at 5:25 PM, Murali Karicheri <m-karicheri2@ti.com> wrote:
> On 01/23/2015 06:41 PM, Bjorn Helgaas wrote:
>>
>> On Fri, Jan 23, 2015 at 05:32:37PM -0500, Murali Karicheri wrote:
>>>
>>> Add of_pci_dma_configure() to allow updating the dma configuration
>>> of the pci device using the configuration from DT of the parent of
>>> the root bridge device.
>>>
>>> Cc: Joerg Roedel<joro@8bytes.org>
>>> Cc: Grant Likely<grant.likely@linaro.org>
>>> Cc: Rob Herring<robh+dt@kernel.org>
>>> Cc: Bjorn Helgaas<bhelgaas@google.com>
>>> Cc: Will Deacon<will.deacon@arm.com>
>>> Cc: Russell King<linux@arm.linux.org.uk>
>>> Cc: Arnd Bergmann<arnd@arndb.de>
>>> Cc: Suravee Suthikulpanit<Suravee.Suthikulpanit@amd.com>
>>>
>>> Signed-off-by: Murali Karicheri<m-karicheri2@ti.com>
>>> ---
>>>   drivers/of/of_pci.c    |   39 +++++++++++++++++++++++++++++++++++++++
>>>   include/linux/of_pci.h |   12 ++++++++++++
>>>   2 files changed, 51 insertions(+)
>>>
>>> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
>>> index 88471d3..34878c9 100644
>>> --- a/drivers/of/of_pci.c
>>> +++ b/drivers/of/of_pci.c
>>> @@ -2,6 +2,7 @@
>>>   #include<linux/export.h>
>>>   #include<linux/of.h>
>>>   #include<linux/of_address.h>
>>> +#include<linux/of_device.h>
>>>   #include<linux/of_pci.h>
>>>   #include<linux/slab.h>
>>>
>>> @@ -229,6 +230,44 @@ parse_failed:
>>>         return err;
>>>   }
>>>   EXPORT_SYMBOL_GPL(of_pci_get_host_bridge_resources);
>>> +
>>> +/**
>>> + * of_get_pci_root_bridge_parent - get the OF node of the root bridge's
>>> parent
>>> + * @dev: ptr to pci_dev struct of the pci device
>>> + *
>>> + * This function will traverse the bus up to the root bus starting with
>>> + * the child and return the OF node ptr to root bridge device's parent
>>> device.
>>> + */
>>> +struct device_node *of_get_pci_root_bridge_parent(struct pci_dev *dev)
>>
>>
>> I'm not an OF person, but this interface seems like it might be too
>> special-purpose.  Maybe it would be enough to add
>> "of_get_pci_root_bridge()", and the caller could do this:
>>
>>      struct device *bridge = of_get_pci_root_bridge(dev);
>>      struct device_node *parent_np = bridge->parent->of_node;
>>
>> Also, the name "of_get_..." suggests that it increments a refcount, as
>> of_get_parent() does.  But you aren't doing anything with the refcount.
>>
>> But I guess an "of_get_pci_root_bridge()" isn't doing anything OF-related,
>> so maybe we should just add a "pci_get_host_bridge(struct pci_dev *)"
>> to PCI instead.
>
>
> Bjorn,
>
> Thanks for the comment.
>
> I think adding pci_get_host_bridge() is a good idea. There is already
> similar function in host-bridge.c. I have added this function re-using
> existing function find_pci_root_bus(). See the incremental diff below after
> this change. Does this look good?

I like the implementation, but I think either we need to take a
reference on the host bridge, or change the name to  something like
"pci_find_host_bridge()", because using "_get_" is conventional for
functions that acquire a reference.

Since host bridges are hot-pluggable, at least in theory, I vote for
taking a reference.  Then of course, you'd have to add code to drop
the reference when you're finished with it.

Bjorn

> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> index 34878c9..77b15b5 100644
> --- a/drivers/of/of_pci.c
> +++ b/drivers/of/of_pci.c
> @@ -232,26 +232,6 @@ parse_failed:
>  EXPORT_SYMBOL_GPL(of_pci_get_host_bridge_resources);
>
>  /**
> - * of_get_pci_root_bridge_parent - get the OF node of the root bridge's
> parent
> - * @dev: ptr to pci_dev struct of the pci device
> - *
> - * This function will traverse the bus up to the root bus starting with
> - * the child and return the OF node ptr to root bridge device's parent
> device.
> - */
> -struct device_node *of_get_pci_root_bridge_parent(struct pci_dev *dev)
> -{
> -       struct pci_bus *bus = dev->bus;
> -       struct device *bridge;
> -
> -       while (!pci_is_root_bus(bus))
> -               bus = bus->parent;
> -       bridge = bus->bridge;
> -
> -       return bridge->parent->of_node;
> -}
> -EXPORT_SYMBOL_GPL(of_get_pci_root_bridge_parent);
> -
> -/**
>   * of_pci_dma_configure - Setup DMA configuration
>   * @dev: ptr to pci_dev struct of the pci device
>   *
> @@ -261,10 +241,9 @@ EXPORT_SYMBOL_GPL(of_get_pci_root_bridge_parent);
>  void of_pci_dma_configure(struct pci_dev *pci_dev)
>  {
>         struct device *dev = &pci_dev->dev;
> -       struct device_node *parent_np;
> +       struct device *bridge = pci_get_host_bridge(pci_dev);
>
> -       parent_np = of_get_pci_root_bridge_parent(pci_dev);
> -       of_dma_configure(dev, parent_np);
> +       of_dma_configure(dev, bridge->parent->of_node);
>  }
>  EXPORT_SYMBOL_GPL(of_pci_dma_configure);
>
> diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c
> index 0e5f3c9..9803aa6 100644
> --- a/drivers/pci/host-bridge.c
> +++ b/drivers/pci/host-bridge.c
> @@ -23,6 +23,13 @@ static struct pci_host_bridge
> *find_pci_host_bridge(struct pci_bus *bus)
>         return to_pci_host_bridge(root_bus->bridge);
>  }
>
> +struct device *pci_get_host_bridge(struct pci_dev *dev)
> +{
> +       struct pci_bus *root_bus = find_pci_root_bus(dev->bus);
> +
> +       return root_bus->bridge;
> +}
> +
>  void pci_set_host_bridge_release(struct pci_host_bridge *bridge,
>                                  void (*release_fn)(struct pci_host_bridge
> *),
>                                  void *release_data)
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 9603094..5bcdfa6 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -513,6 +513,8 @@ static inline struct pci_dev *pci_upstream_bridge(struct
> pci_dev *dev)
>         return dev->bus->self;
>  }
>
> +struct device *pci_get_host_bridge(struct pci_dev *dev);
> +
>  #ifdef CONFIG_PCI_MSI
>  static inline bool pci_dev_msi_enabled(struct pci_dev *pci_dev)
>  {
> @@ -1823,6 +1825,7 @@ int pci_vpd_find_tag(const u8 *buf, unsigned int off,
> unsigned int len, u8 rdt);
>  int pci_vpd_find_info_keyword(const u8 *buf, unsigned int off,
>                               unsigned int len, const char *kw);
>
>  /* PCI <-> OF binding helpers */
>  #ifdef CONFIG_OF
>  struct device_node;
>
>
>>
>> Bjorn
>>
>>> +{
>>> +       struct pci_bus *bus = dev->bus;
>>> +       struct device *bridge;
>>> +
>>> +       while (!pci_is_root_bus(bus))
>>> +               bus = bus->parent;
>>> +       bridge = bus->bridge;
>>> +
>>> +       return bridge->parent->of_node;
>>> +}
>>> +EXPORT_SYMBOL_GPL(of_get_pci_root_bridge_parent);
>>> +
>>> +/**
>>> + * of_pci_dma_configure - Setup DMA configuration
>>> + * @dev: ptr to pci_dev struct of the pci device
>>> + *
>>> + * Function to update PCI devices's DMA configuration using the same
>>> + * info from the OF node of root host bridge's parent.
>>> + */
>>> +void of_pci_dma_configure(struct pci_dev *pci_dev)
>>> +{
>>> +       struct device *dev =&pci_dev->dev;
>>>
>>> +       struct device_node *parent_np;
>>> +
>>> +       parent_np = of_get_pci_root_bridge_parent(pci_dev);
>>> +       of_dma_configure(dev, parent_np);
>>> +}
>>> +EXPORT_SYMBOL_GPL(of_pci_dma_configure);
>>> +
>>>   #endif /* CONFIG_OF_ADDRESS */
>>>
>>>   #ifdef CONFIG_PCI_MSI
>>> diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
>>> index ce0e5ab..0465a2a 100644
>>> --- a/include/linux/of_pci.h
>>> +++ b/include/linux/of_pci.h
>>> @@ -16,6 +16,8 @@ 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);
>>> +struct device_node *of_get_pci_root_bridge_parent(struct pci_dev *dev);
>>> +void of_pci_dma_configure(struct pci_dev *pci_dev);
>>>   #else
>>>   static inline int of_irq_parse_pci(const struct pci_dev *pdev, struct
>>> of_phandle_args *out_irq)
>>>   {
>>> @@ -50,6 +52,16 @@ of_get_pci_domain_nr(struct device_node *node)
>>>   {
>>>         return -1;
>>>   }
>>> +
>>> +static inline struct device_node
>>> +*of_get_pci_root_bridge_parent(struct pci_dev *dev)
>>> +{
>>> +       return NULL;
>>> +}
>>> +
>>> +static inline void of_pci_dma_configure(struct pci_dev *pci_dev)
>>> +{
>>> +}
>>>   #endif
>>>
>>>   #if defined(CONFIG_OF_ADDRESS)
>>> --
>>> 1.7.9.5
>>>
>
>
> --
> Murali Karicheri
> Linux Kernel, Texas Instruments