[PATCH] Update PCI IOMEM allocation start

This fixes the problem with "Averatec 6240 pcmcia_socket0: unable to
apply power", which was due to the CardBus IOMEM register region being
allocated at an address that was actually inside the RAM window that had
been reserved for video frame-buffers in an UMA setup.

The BIOS _should_ have marked that region reserved in the e820 memory
descriptor tables, but did not.

It is fixed by rounding up the default starting address of PCI memory
allocations, so that we leave a bigger gap after the final known memory
location.  The amount of rounding depends on how big the unused memory
gap is that we can allocate IOMEM from.

Based on example code by Linus.

Acked-by: Greg KH <greg@kroah.com>
Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
index 116ac5f..bb0ae18 100644
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -567,7 +567,7 @@ unsigned long pci_mem_start = 0xaeedbabe;
  */
 __init void e820_setup_gap(void)
 {
-	unsigned long gapstart, gapsize;
+	unsigned long gapstart, gapsize, round;
 	unsigned long last;
 	int i;
 	int found = 0;
@@ -604,14 +604,14 @@ __init void e820_setup_gap(void)
 	}
 
 	/*
-	 * Start allocating dynamic PCI memory a bit into the gap,
-	 * aligned up to the nearest megabyte.
-	 *
-	 * Question: should we try to pad it up a bit (do something
-	 * like " + (gapsize >> 3)" in there too?). We now have the
-	 * technology.
+	 * See how much we want to round up: start off with
+	 * rounding to the next 1MB area.
 	 */
-	pci_mem_start = (gapstart + 0xfffff) & ~0xfffff;
+	round = 0x100000;
+	while ((gapsize >> 4) > round)
+		round += round;
+	/* Fun with two's complement */
+	pci_mem_start = (gapstart + round) & -round;
 
 	printk(KERN_INFO "Allocating PCI resources starting at %lx (gap: %lx:%lx)\n",
 		pci_mem_start, gapstart, gapsize);