linux-kernel - Re: [PATCH] pci: Add support for creating a generic host

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Message-ID: <7398333.9L5KlyFggU@wuerfel>
Date:	Mon, 03 Feb 2014 19:46:10 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Liviu Dudau <Liviu.Dudau@....com>
Cc:	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH] pci: Add support for creating a generic host_bridge from device tree

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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