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Commit 67d29b5c authored by Bjorn Helgaas's avatar Bjorn Helgaas
Browse files

PCI: Add resource allocation comments 



Add comments in the code to match the allocation strategy of 7c671426dfc3
("PCI: Restrict 64-bit prefetchable bridge windows to 64-bit resources").

No functional change.

Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent d3689df0

drivers/pci/setup-bus.c

+43 −15
Original line number Diff line number Diff line
@@ -1164,17 +1164,16 @@ void __ref __pci_bus_size_bridges(struct pci_bus *bus, 
			additional_io_size  = pci_hotplug_io_size;

			additional_mem_size = pci_hotplug_mem_size;

		}

		/*

		 * Follow thru

		 */

		/* Fall through */

	default:

		pbus_size_io(bus, realloc_head ? 0 : additional_io_size,

			     additional_io_size, realloc_head);

		/* If the bridge supports prefetchable range, size it

		   separately. If it doesn't, or its prefetchable window

		   has already been allocated by arch code, try

		   non-prefetchable range for both types of PCI memory

		   resources. */



		/*

		 * If there's a 64-bit prefetchable MMIO window, compute

		 * the size required to put all 64-bit prefetchable

		 * resources in it.

		 */

		b_res = &bus->self->resource[PCI_BRIDGE_RESOURCES];

		mask = IORESOURCE_MEM;

		prefmask = IORESOURCE_MEM | IORESOURCE_PREFETCH;
@@ -1184,29 +1183,58 @@ void __ref __pci_bus_size_bridges(struct pci_bus *bus, 
				  prefmask, prefmask,

				  realloc_head ? 0 : additional_mem_size,

				  additional_mem_size, realloc_head);

			if (ret == 0) {



			/*

				 * Success, with pref mmio64,

				 * next will size non-pref or

				 * non-mmio64 */

			 * If successful, all non-prefetchable resources

			 * and any 32-bit prefetchable resources will go in

			 * the non-prefetchable window.

			 */

			if (ret == 0) {

				mask = prefmask;

				type2 = prefmask & ~IORESOURCE_MEM_64;

				type3 = prefmask & ~IORESOURCE_PREFETCH;

			}

		}



		/*

		 * If there is no 64-bit prefetchable window, compute the

		 * size required to put all prefetchable resources in the

		 * 32-bit prefetchable window (if there is one).

		 */

		if (!type2) {

			prefmask &= ~IORESOURCE_MEM_64;

			ret = pbus_size_mem(bus, prefmask, prefmask,

					 prefmask, prefmask,

					 realloc_head ? 0 : additional_mem_size,

					 additional_mem_size, realloc_head);

			if (ret == 0) {

				/* Success, next will size non-prefetch. */



			/*

			 * If successful, only non-prefetchable resources

			 * will go in the non-prefetchable window.

			 */

			if (ret == 0)

				mask = prefmask;

			} else

			else

				additional_mem_size += additional_mem_size;



			type2 = type3 = IORESOURCE_MEM;

		}



		/*

		 * Compute the size required to put everything else in the

		 * non-prefetchable window.  This includes:

		 *

		 *   - all non-prefetchable resources

		 *   - 32-bit prefetchable resources if there's a 64-bit

		 *     prefetchable window or no prefetchable window at all

		 *   - 64-bit prefetchable resources if there's no

		 *     prefetchable window at all

		 *

		 * Note that the strategy in __pci_assign_resource() must

		 * match that used here.  Specifically, we cannot put a

		 * 32-bit prefetchable resource in a 64-bit prefetchable

		 * window.

		 */

		pbus_size_mem(bus, mask, IORESOURCE_MEM, type2, type3,

				realloc_head ? 0 : additional_mem_size,

				additional_mem_size, realloc_head);

drivers/pci/setup-res.c

+19 −16
Original line number Diff line number Diff line
@@ -209,20 +209,25 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, 


	min = (res->flags & IORESOURCE_IO) ? PCIBIOS_MIN_IO : PCIBIOS_MIN_MEM;



	/* First, try exact prefetching match.. */

	/*

	 * First, try exact prefetching match.  Even if a 64-bit

	 * prefetchable bridge window is below 4GB, we can't put a 32-bit

	 * prefetchable resource in it because pbus_size_mem() assumes a

	 * 64-bit window will contain no 32-bit resources.  If we assign

	 * things differently than they were sized, not everything will fit.

	 */

	ret = pci_bus_alloc_resource(bus, res, size, align, min,

				     IORESOURCE_PREFETCH | IORESOURCE_MEM_64,

				     pcibios_align_resource, dev);

	if (ret == 0)

		return 0;



	if ((res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) ==

	     (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) {

	/*

		 * That failed.

		 *

		 * Try 32bit pref

	 * If the prefetchable window is only 32 bits wide, we can put

	 * 64-bit prefetchable resources in it.

	 */

	if ((res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) ==

	     (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) {

		ret = pci_bus_alloc_resource(bus, res, size, align, min,

					     IORESOURCE_PREFETCH,

					     pcibios_align_resource, dev);
@@ -230,18 +235,16 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, 
			return 0;

	}



	if (res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) {

	/*

		 * That failed.

		 *

		 * But a prefetching area can handle a non-prefetching

		 * window (it will just not perform as well).

		 *

		 * Also can put 64bit under 32bit range. (below 4g).

	 * If we didn't find a better match, we can put any memory resource

	 * in a non-prefetchable window.  If this resource is 32 bits and

	 * non-prefetchable, the first call already tried the only possibility

	 * so we don't need to try again.

	 */

	if (res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64))

		ret = pci_bus_alloc_resource(bus, res, size, align, min, 0,

					     pcibios_align_resource, dev);

	}



	return ret;

}