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

[Bjorn Helgaas <bhelgaas@google.com>]

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

> +{
> +	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
>