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SubjectRe: [PATCH 2/2] acpi based pci gap caluculation v2
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On Tue, 2008-06-24 at 11:48 -0700, Alok Kataria wrote:
> Evaluates the _CRS object under PCI0 looking for producer resources.
> Then searches the e820 memory space for a gap within these producer resources.
>
> Allows us to find a gap for the unclaimed pci resources or MMIO resources
> for hotplug devices within the BIOS allowed pci regions.
>
> v1->v2: Some changes in the print strings.
> Also note the prototype for e820_search_gap has changes in this
> iteration, but the return value is ignored while calling it over here.
>
> Signed-off-by: Alok N Kataria <akataria@vmware.com>
>
> Index: linux-x86-tree.git/arch/x86/pci/acpi.c
> ===================================================================
> --- linux-x86-tree.git.orig/arch/x86/pci/acpi.c 2008-06-23 17:24:07.000000000 -0700
> +++ linux-x86-tree.git/arch/x86/pci/acpi.c 2008-06-24 10:57:43.000000000 -0700
> @@ -4,6 +4,7 @@
> #include <linux/irq.h>
> #include <linux/dmi.h>
> #include <asm/numa.h>
> +#include <asm/e820.h>
> #include "pci.h"
>
> struct pci_root_info {
> @@ -14,6 +15,11 @@
> int busnum;
> };
>
> +struct gap_info {
> + unsigned long gapstart;
> + unsigned long gapsize;
> +};
> +
> static acpi_status
> resource_to_addr(struct acpi_resource *resource,
> struct acpi_resource_address64 *addr)
> @@ -110,6 +116,70 @@
> }
> }
>
> +static acpi_status search_gap(struct acpi_resource *resource, void *data)
> +{
> + struct acpi_resource_address64 addr;
> + acpi_status status;
> + struct gap_info *gap = data;
> +
> + status = resource_to_addr(resource, &addr);
> + if (ACPI_SUCCESS(status) &&
> + addr.resource_type == ACPI_MEMORY_RANGE &&
> + addr.address_length > gap->gapsize) {
> + e820_search_gap(&gap->gapstart, &gap->gapsize,
> + (addr.minimum + addr.translation_offset));
> + }
> +
> + return AE_OK;
> +}
> +
> +/*
> + * Search for a hole in the 32 bit address space for PCI to assign MMIO
> + * resources for hotplug or unconfigured resources.
> + * We query the CRS object of the PCI root device to look for possible producer
> + * resources in the tree and consider these while calulating the start address
> + * for this hole.
> + */
> +static void pci_setup_gap(acpi_handle *handle)
> +{
> + struct gap_info gap;
> + acpi_status status;
> +
> + gap.gapstart = 0;
> + gap.gapsize = 0x400000;
> +
> + status = acpi_walk_resources(handle, METHOD_NAME__CRS,
> + search_gap, &gap);
> +
> + if (ACPI_SUCCESS(status)) {
> + unsigned long round;
> +
> + if (!gap.gapstart) {
> + printk(KERN_ERR "ACPI: Warning: Cannot find a gap "
> + "in the 32bit address range for PCI\n"
> + "ACPI: PCI devices may collide with "
> + "hotpluggable memory address range\n");
> + }
> + /*
> + * Round the gapstart, uses the same logic as in
> + * e820_gap_setup
> + */
> + round = 0x100000;
> + while ((gap.gapsize >> 4) > round)
> + round += round;
> + /* Fun with two's complement */
> + pci_mem_start = (gap.gapstart + round) & -round;
> +
> + printk(KERN_INFO "ACPI: PCI resources should "
> + "start at %lx (gap: %lx:%lx)\n",
> + pci_mem_start, gap.gapstart, gap.gapsize);
> + } else {
> + printk(KERN_ERR "ACPI: Error while searching for gap in "
> + "the 32bit address range for PCI\n");
> + }
> +}
> +
> +
> static void
> get_current_resources(struct acpi_device *device, int busnum,
> int domain, struct pci_bus *bus)
> @@ -220,6 +290,8 @@
>
> if (bus && (pci_probe & PCI_USE__CRS))
> get_current_resources(device, busnum, domain, bus);
> +
> + pci_setup_gap(device->handle);
> return bus;
> }
It seems reasonable.
But if the resource obtained from the PCI0 _CRS method is incorrect, we
will get the incorrect pci_mem_start.

At the same time after the patch is applied, pci_mem_start will be
parsed in two different ways. If the result is different, maybe the
incorrect pci_mem_start will be used.

Best regards.
Yakui
>
>
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