From 67d29b5c6c40e91b124695e9250c2fd24915e24a Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Mon, 19 May 2014 18:32:18 -0600 Subject: [PATCH] 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 --- drivers/pci/setup-bus.c | 58 ++++++++++++++++++++++++++++++----------- drivers/pci/setup-res.c | 35 +++++++++++++------------ 2 files changed, 62 insertions(+), 31 deletions(-) diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c index 12ab50ffdfea..455ee0364956 100644 --- a/drivers/pci/setup-bus.c +++ b/drivers/pci/setup-bus.c @@ -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 successful, all non-prefetchable resources + * and any 32-bit prefetchable resources will go in + * the non-prefetchable window. + */ if (ret == 0) { - /* - * Success, with pref mmio64, - * next will size non-pref or - * non-mmio64 */ 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); diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c index 3bdac9dc4a88..3da2542eb4df 100644 --- a/drivers/pci/setup-res.c +++ b/drivers/pci/setup-res.c @@ -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 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)) { - /* - * That failed. - * - * Try 32bit pref - */ 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; } -- 2.30.2