Devicetree

* Re: [PATCH] pci: Add support for creating a generic host_bridge from device tree
From: Tanmay Inamdar @ 2014-02-05 22:26 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Liviu Dudau, devicetree@vger.kernel.org, linaro-kernel, linux-pci,
	Will Deacon, LKML, Catalin Marinas, Bjorn Helgaas, LAKML
In-Reply-To: <7398333.9L5KlyFggU@wuerfel>

Hello Liviu,

I did not get the first email of this particular patch on any of
subscribed mailing lists (don't know why), hence replying here.

+struct pci_host_bridge *
+pci_host_bridge_of_init(struct device *parent, int busno, struct pci_ops *ops,
+ void *host_data, struct list_head *resources)
+{
+ struct pci_bus *root_bus;
+ struct pci_host_bridge *bridge;
+
+ /* first parse the host bridge bus ranges */
+ if (pci_host_bridge_of_get_ranges(parent->of_node, resources))
+ return NULL;
+
+ /* then create the root bus */
+ root_bus = pci_create_root_bus(parent, busno, ops, host_data, resources);
+ if (!root_bus)
+ return NULL;
+
+ bridge = to_pci_host_bridge(root_bus->bridge);
+
+ return bridge;
+}

You are keeping the domain_nr inside pci_host_bridge structure. In
above API, domain_nr is required in 'pci_find_bus' function called
from 'pci_create_root_bus'. Since the bridge is allocated after
creating root bus, 'pci_find_bus' always gets domain_nr as 0. This
will cause problem for scanning multiple domains.

On Mon, Feb 3, 2014 at 10:46 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Monday 03 February 2014 18:33:48 Liviu Dudau wrote:
>> +/**
>> + * 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
>> + *
>> + * 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 will then apply their filtering based on the limitations
>> + * of each platform. One general restriction seems to be the number of IO space
>> + * ranges, the PCI framework makes intensive use of struct resource management,
>> + * and for IORESOURCE_IO types they can only be requested if they are contained
>> + * within the global ioport_resource, so that should be limited to one IO space
>> + * range.
>
> Actually we have quite a different set of restrictions around I/O space on ARM32
> at the moment: Each host bridge can have its own 64KB range in an arbitrary
> location on MMIO space, and the total must not exceed 2MB of I/O space.
>
>> + */
>> +static int pci_host_bridge_of_get_ranges(struct device_node *dev,
>> +                                     struct list_head *resources)
>> +{
>> +     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
>> +              * (some FW try to feed us with non sensical zero sized regions
>> +              * such as power3 which look like some kind of attempt
>> +              * at exposing the VGA memory hole) 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);
>> +
>> +             pci_add_resource_offset(resources, res,
>> +                             range.cpu_addr - range.pci_addr);
>> +     }
>
> I believe of_pci_range_to_resource() will return the MMIO aperture for the
> I/O space window here, which is not what you are supposed to pass into
> pci_add_resource_offset.
>
>> +EXPORT_SYMBOL(pci_host_bridge_of_init);
>
> EXPORT_SYMBOL_GPL
>
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index 6e34498..16febae 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -1787,6 +1787,17 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>>       list_for_each_entry_safe(window, n, resources, list) {
>>               list_move_tail(&window->list, &bridge->windows);
>>               res = window->res;
>> +             /*
>> +              * IO resources are stored in the kernel with a CPU start
>> +              * address of zero. Adjust the data accordingly and remember
>> +              * the offset
>> +              */
>> +             if (resource_type(res) == IORESOURCE_IO) {
>> +                     bridge->io_offset = res->start;
>> +                     res->end -= res->start;
>> +                     window->offset -= res->start;
>> +                     res->start = 0;
>> +             }
>>               offset = window->offset;
>>               if (res->flags & IORESOURCE_BUS)
>
> Won't this break all existing host bridges?
>
>         Arnd
>
> _______________________________________________
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> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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