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>diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 12ab50f..455ee03 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1164,17 +1164,16 @@
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 @@
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);