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SubjectRe: [PATCH v2 4/4] pci: Add support for creating a generic host_bridge from device tree
Date
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@arm.com>

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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