Commit 809d9a8f authored by Alok Kataria's avatar Alok Kataria Committed by Jesse Barnes
Browse files

x86/PCI: ACPI based PCI gap calculation 



Using ACPI to find free address space allows us to find a gap for the
unallocated PCI resources or MMIO resources for hotplug devices within
the BIOS allowed PCI regions.

It works by evaluating the _CRS object under PCI0 looking for producer
resources.  Then searches the e820 memory space for a gap within these
producer resources.

Signed-off-by: default avatarAlok N Kataria <akataria@vmware.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
parent c300bd2f

arch/x86/pci/acpi.c

+80 −0
Original line number Diff line number Diff line
@@ -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 @@ struct pci_root_info { 
	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 +116,78 @@ adjust_transparent_bridge_resources(struct pci_bus *bus) 
	}

}



static acpi_status search_gap(struct acpi_resource *resource, void *data)

{

	struct acpi_resource_address64 addr;

	acpi_status status;

	struct gap_info *gap = data;

	unsigned long long start_addr, end_addr;



	status = resource_to_addr(resource, &addr);

	if (ACPI_SUCCESS(status) &&

	    addr.resource_type == ACPI_MEMORY_RANGE &&

	    addr.address_length > gap->gapsize) {

		start_addr = addr.minimum + addr.translation_offset;

		/*

		 * We want space only in the 32bit address range

		 */

		if (start_addr < UINT_MAX) {

			end_addr = start_addr + addr.address_length;

			e820_search_gap(&gap->gapstart, &gap->gapsize,

					start_addr, end_addr);

		}

	}



	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)
@@ -215,6 +293,8 @@ struct pci_bus * __devinit pci_acpi_scan_root(struct acpi_device *device, int do 


	if (bus && (pci_probe & PCI_USE__CRS))

		get_current_resources(device, busnum, domain, bus);



	pci_setup_gap(device->handle);

	return bus;

}

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