[PATCH] PCI: disable decoding while sizing BARs

[Bjorn Helgaas]

While sizing BARs, devices are temporarily assigned ranges
that may conflict with other things in the system, like IOSAPICs.
Here's a detailed description of a hang that results from leaving
device decoding enabled while sizing the BARs:

    https://lists.linuxia64.org/archives//linux-ia64/2002-April/003302.html

This patch applies to current 2.4 BitKeeper.

--- linux-2.4/drivers/pci/pci.c	2002-12-16 10:44:21.000000000 -0700
+++ testing/drivers/pci/pci.c	2002-12-16 17:22:26.000000000 -0700
@@ -1058,8 +1058,14 @@
 {
 	unsigned int pos, reg, next;
 	u32 l, sz;
+	u16 cmd;
 	struct resource *res;
 
+	/* Disable I/O & memory decoding while we size the BARs. */
+	pci_read_config_word(dev, PCI_COMMAND, &cmd);
+	pci_write_config_word(dev, PCI_COMMAND,
+		cmd & ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY));
+
 	for(pos=0; pos<howmany; pos = next) {
 		next = pos+1;
 		res = &dev->resource[pos];
@@ -1131,6 +1137,8 @@
 			res->end = res->start + (unsigned long) sz;
 		}
 	}
+
+	pci_write_config_word(dev, PCI_COMMAND, cmd);
 }
 
 void __devinit pci_read_bridge_bases(struct pci_bus *child)