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: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Bjorn Helgaas
parent
d3689df044
commit
67d29b5c6c
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@ -1164,17 +1164,16 @@ void __ref __pci_bus_size_bridges(struct pci_bus *bus,
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additional_io_size = pci_hotplug_io_size;
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additional_mem_size = pci_hotplug_mem_size;
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}
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/*
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* Follow thru
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*/
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/* Fall through */
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default:
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pbus_size_io(bus, realloc_head ? 0 : additional_io_size,
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additional_io_size, realloc_head);
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/* If the bridge supports prefetchable range, size it
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separately. If it doesn't, or its prefetchable window
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has already been allocated by arch code, try
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non-prefetchable range for both types of PCI memory
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resources. */
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/*
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* If there's a 64-bit prefetchable MMIO window, compute
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* the size required to put all 64-bit prefetchable
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* resources in it.
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*/
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b_res = &bus->self->resource[PCI_BRIDGE_RESOURCES];
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mask = IORESOURCE_MEM;
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prefmask = IORESOURCE_MEM | IORESOURCE_PREFETCH;
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@ -1184,29 +1183,58 @@ void __ref __pci_bus_size_bridges(struct pci_bus *bus,
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prefmask, prefmask,
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realloc_head ? 0 : additional_mem_size,
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additional_mem_size, realloc_head);
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/*
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* If successful, all non-prefetchable resources
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* and any 32-bit prefetchable resources will go in
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* the non-prefetchable window.
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*/
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if (ret == 0) {
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/*
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* Success, with pref mmio64,
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* next will size non-pref or
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* non-mmio64 */
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mask = prefmask;
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type2 = prefmask & ~IORESOURCE_MEM_64;
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type3 = prefmask & ~IORESOURCE_PREFETCH;
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}
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}
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/*
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* If there is no 64-bit prefetchable window, compute the
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* size required to put all prefetchable resources in the
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* 32-bit prefetchable window (if there is one).
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*/
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if (!type2) {
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prefmask &= ~IORESOURCE_MEM_64;
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ret = pbus_size_mem(bus, prefmask, prefmask,
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prefmask, prefmask,
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realloc_head ? 0 : additional_mem_size,
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additional_mem_size, realloc_head);
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if (ret == 0) {
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/* Success, next will size non-prefetch. */
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/*
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* If successful, only non-prefetchable resources
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* will go in the non-prefetchable window.
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*/
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if (ret == 0)
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mask = prefmask;
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} else
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else
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additional_mem_size += additional_mem_size;
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type2 = type3 = IORESOURCE_MEM;
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}
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/*
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* Compute the size required to put everything else in the
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* non-prefetchable window. This includes:
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*
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* - all non-prefetchable resources
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* - 32-bit prefetchable resources if there's a 64-bit
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* prefetchable window or no prefetchable window at all
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* - 64-bit prefetchable resources if there's no
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* prefetchable window at all
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*
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* Note that the strategy in __pci_assign_resource() must
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* match that used here. Specifically, we cannot put a
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* 32-bit prefetchable resource in a 64-bit prefetchable
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* window.
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*/
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pbus_size_mem(bus, mask, IORESOURCE_MEM, type2, type3,
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realloc_head ? 0 : additional_mem_size,
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additional_mem_size, realloc_head);
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@ -209,20 +209,25 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev,
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min = (res->flags & IORESOURCE_IO) ? PCIBIOS_MIN_IO : PCIBIOS_MIN_MEM;
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/* First, try exact prefetching match.. */
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/*
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* First, try exact prefetching match. Even if a 64-bit
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* prefetchable bridge window is below 4GB, we can't put a 32-bit
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* prefetchable resource in it because pbus_size_mem() assumes a
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* 64-bit window will contain no 32-bit resources. If we assign
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* things differently than they were sized, not everything will fit.
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*/
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ret = pci_bus_alloc_resource(bus, res, size, align, min,
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IORESOURCE_PREFETCH | IORESOURCE_MEM_64,
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pcibios_align_resource, dev);
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if (ret == 0)
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return 0;
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/*
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* If the prefetchable window is only 32 bits wide, we can put
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* 64-bit prefetchable resources in it.
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*/
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if ((res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) ==
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(IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) {
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/*
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* That failed.
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*
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* Try 32bit pref
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*/
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ret = pci_bus_alloc_resource(bus, res, size, align, min,
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IORESOURCE_PREFETCH,
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pcibios_align_resource, dev);
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@ -230,18 +235,16 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev,
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return 0;
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}
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if (res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) {
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/*
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* That failed.
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*
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* But a prefetching area can handle a non-prefetching
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* window (it will just not perform as well).
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*
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* Also can put 64bit under 32bit range. (below 4g).
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*/
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/*
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* If we didn't find a better match, we can put any memory resource
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* in a non-prefetchable window. If this resource is 32 bits and
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* non-prefetchable, the first call already tried the only possibility
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* so we don't need to try again.
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*/
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if (res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64))
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ret = pci_bus_alloc_resource(bus, res, size, align, min, 0,
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pcibios_align_resource, dev);
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}
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return ret;
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}
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