Re: [PATCH v2 4/4] pci: Add support for creating a generic host_bridge from device tree

[Arnd Bergmann]

On Thursday 27 February 2014 13:06:42 Liviu Dudau wrote:
> Several platforms use a rather generic version of parsing
> the device tree to find the host bridge ranges. Move the common code
> into the generic PCI code and use it to create a pci_host_bridge
> structure that can be used by arch code.
> 
> Based on early attempts by Andrew Murray to unify the code.
> Used powerpc and microblaze PCI code as starting point.
> 
> Signed-off-by: Liviu Dudau <Liviu.Dudau@xxxxxxx>

Please add Benjamin Herrenschmidt to Cc here, I think it would be helpful
to get his input so we can make this work on powerpc as well.

> diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c
> index 06ace62..feb8436 100644
> --- a/drivers/pci/host-bridge.c
> +++ b/drivers/pci/host-bridge.c
> @@ -6,9 +6,13 @@
>  #include <linux/init.h>
>  #include <linux/pci.h>
>  #include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_pci.h>
>  
>  #include "pci.h"
>  
> +static int domain_nr;
> +

For correctness, I think you want an 'atomic_t' here and use
atomic_inc_return() to get a new value.

>  static struct pci_bus *find_pci_root_bus(struct pci_bus *bus)
>  {
>  	while (bus->parent)
> @@ -91,3 +95,133 @@ void pcibios_bus_to_resource(struct pci_bus *bus, struct resource *res,
>  	res->end = region->end + offset;
>  }
>  EXPORT_SYMBOL(pcibios_bus_to_resource);
> +
> +/**
> + * pci_host_bridge_of_get_ranges - Parse PCI host bridge resources from DT
> + * @dev: device node of the host bridge having the range property
> + * @resources: list where the range of resources will be added after DT parsing
> + * @io_base: pointer to a variable that will contain the physical address for
> + * the start of the I/O range.
> + *
> + * If this function returns an error then the @resources list will be freed.
> + *
> + * This function will parse the "ranges" property of a PCI host bridge device
> + * node and setup the resource mapping based on its content. It is expected
> + * that the property conforms with the Power ePAPR document.
> + *
> + * Each architecture is then offered the chance of applying their own
> + * filtering of pci_host_bridge_windows based on their own restrictions by
> + * calling pcibios_fixup_bridge_ranges(). The filtered list of windows
> + * can then be used when creating a pci_host_bridge structure.
> + */
> +static int pci_host_bridge_of_get_ranges(struct device_node *dev,
> +		struct list_head *resources, resource_size_t *io_base)
> +{
> +	struct resource *res;
> +	struct of_pci_range range;
> +	struct of_pci_range_parser parser;
> +	int err;
> +
> +	pr_info("PCI host bridge %s ranges:\n", dev->full_name);
> +
> +	/* Check for ranges property */
> +	err = of_pci_range_parser_init(&parser, dev);
> +	if (err)
> +		return err;
> +
> +	pr_debug("Parsing ranges property...\n");
> +	for_each_of_pci_range(&parser, &range) {
> +		/* Read next ranges element */
> +		pr_debug("pci_space: 0x%08x pci_addr:0x%016llx ",
> +				range.pci_space, range.pci_addr);
> +		pr_debug("cpu_addr:0x%016llx size:0x%016llx\n",
> +					range.cpu_addr, range.size);
> +
> +		/*
> +		 * If we failed translation or got a zero-sized region
> +		 * then skip this range
> +		 */
> +		if (range.cpu_addr == OF_BAD_ADDR || range.size == 0)
> +			continue;
> +
> +		res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> +		if (!res) {
> +			err = -ENOMEM;
> +			goto bridge_ranges_nomem;
> +		}
> +
> +		of_pci_range_to_resource(&range, dev, res);
> +
> +		if (resource_type(res) == IORESOURCE_IO)
> +			*io_base = range.cpu_addr;
> +
> +		pci_add_resource_offset(resources, res,
> +				res->start - range.pci_addr);
> +	}

This is not the correct resource for I/O space at all. Please talk
to Will, I've been over this with him in detail and he probably
understands it now. I assume you are both working in the same
building.

Since this is common PCI code, you could also decide to open-code
the pci_add_resource_offset() function. If you don't do that, I
think you have a memory leak for the resources that you can avoid
by allocating the resource and pci_host_bridge_window structures
together with a single kzalloc.

> +	/* Apply architecture specific fixups for the ranges */
> +	pcibios_fixup_bridge_ranges(resources);
> +
> +	return 0;
> +
> +bridge_ranges_nomem:
> +	pci_free_resource_list(resources);
> +	return err;
> +}
> +
> +/**
> + * of_create_pci_host_bridge - Create a PCI host bridge structure using
> + * information passed in the DT.
> + * @parent: device owning this host bridge
> + * @ops: pci_ops associated with the host controller
> + * @host_data: opaque data structure used by the host controller.
> + *
> + * returns a pointer to the newly created pci_host_bridge structure, or
> + * NULL if the call failed.
> + *
> + * This function will try to obtain the host bridge domain number by
> + * using of_alias_get_id() call with "pci-domain" as a stem. If that
> + * fails, a local allocator will be used that will put each host bridge
> + * in a new domain.
> + */
> +struct pci_host_bridge *
> +of_create_pci_host_bridge(struct device *parent, struct pci_ops *ops, void *host_data)
> +{
> +	int err, domain, busno;
> +	struct resource bus_range;
> +	struct pci_bus *root_bus;
> +	struct pci_host_bridge *bridge;
> +	resource_size_t io_base;
> +	LIST_HEAD(res);
> +
> +	domain = of_alias_get_id(parent->of_node, "pci-domain");
> +	if (domain == -ENODEV)
> +		domain = domain_nr++;
> +
> +	err = of_pci_parse_bus_range(parent->of_node, &bus_range);
> +	if (err) {
> +		dev_info(parent, "No bus range for %s, using default [0-255]\n",
> +			parent->of_node->full_name);
> +		bus_range.start = 0;
> +		bus_range.end = 255;
> +		bus_range.flags = IORESOURCE_BUS;
> +	}
> +	busno = bus_range.start;
> +	pci_add_resource(&res, &bus_range);
> +
> +	/* now parse the rest of host bridge bus ranges */
> +	if (pci_host_bridge_of_get_ranges(parent->of_node, &res, &io_base))
> +		return NULL;
> +
> +	/* then create the root bus */
> +	root_bus = pci_create_root_bus_in_domain(parent, domain, busno,
> +						ops, host_data, &res);
> +	if (!root_bus)
> +		return NULL;

Do we have any code that checks for conflicting domain/bus numbers here?
I guess pci_create_root_bus_in_domain() will fail if you have that.

Since pci_create_root_bus_in_domain() is a new function that you just
introduced, it would be helpful to change the calling conventions
so it returns an error pointer instead of NULL upon failing.
of_create_pci_host_bridge() can do the same, but pci_create_root_bus()
should keep returning NULL so we don't have to change all the
callers.

> +	bridge = to_pci_host_bridge(root_bus->bridge);
> +	bridge->io_base = io_base;
> +
> +	return bridge;
> +}
> +EXPORT_SYMBOL_GPL(of_create_pci_host_bridge);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 1eed009..0c5e269 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -395,6 +395,7 @@ struct pci_host_bridge {
>  	struct device dev;
>  	struct pci_bus *bus;		/* root bus */
>  	int domain_nr;
> +	resource_size_t io_base;	/* physical address for the start of I/O area */
>  	struct list_head windows;	/* pci_host_bridge_windows */
>  	void (*release_fn)(struct pci_host_bridge *);
>  	void *release_data;

What is the io_base used for here?

> @@ -1786,11 +1787,23 @@ static inline struct device_node *pci_bus_to_OF_node(struct pci_bus *bus)
>  	return bus ? bus->dev.of_node : NULL;
>  }
>  
> +struct pci_host_bridge *
> +of_create_pci_host_bridge(struct device *parent, struct pci_ops *ops,
> +			void *host_data);
> +
> +void pcibios_fixup_bridge_ranges(struct list_head *resources);
>  #else /* CONFIG_OF */
>  static inline void pci_set_of_node(struct pci_dev *dev) { }
>  static inline void pci_release_of_node(struct pci_dev *dev) { }
>  static inline void pci_set_bus_of_node(struct pci_bus *bus) { }
>  static inline void pci_release_bus_of_node(struct pci_bus *bus) { }
> +
> +static inline struct pci_host_bridge *
> +pci_host_bridge_of_init(struct device *parent, struct pci_ops *ops,
> +			void *host_data)
> +{
> +	return NULL;
> +}
>  #endif  /* CONFIG_OF */
>  
>  #ifdef CONFIG_EEH
> 

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