[PATCH] x86_64: Port over e820 gap detection from i386

[linux-2.6.git] / arch / x86_64 / kernel / e820.c

diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
index 657003e461e676fd6388153a72b07b02468749bc..56516ac92e5d4b514d59aec823ea9767729180bf 100644 (file)
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -511,3 +511,62 @@ void __init parse_memopt(char *p, char **from)
        end_user_pfn >>= PAGE_SHIFT;    
 } 
 
+unsigned long pci_mem_start = 0xaeedbabe;
+
+/*
+ * Search for the biggest gap in the low 32 bits of the e820
+ * memory space.  We pass this space to PCI to assign MMIO resources
+ * for hotplug or unconfigured devices in.
+ * Hopefully the BIOS let enough space left.
+ */
+__init void e820_setup_gap(void)
+{
+       unsigned long gapstart, gapsize;
+       unsigned long last;
+       int i;
+       int found = 0;
+
+       last = 0x100000000ull;
+       gapstart = 0x10000000;
+       gapsize = 0x400000;
+       i = e820.nr_map;
+       while (--i >= 0) {
+               unsigned long long start = e820.map[i].addr;
+               unsigned long long end = start + e820.map[i].size;
+
+               /*
+                * Since "last" is at most 4GB, we know we'll
+                * fit in 32 bits if this condition is true
+                */
+               if (last > end) {
+                       unsigned long gap = last - end;
+
+                       if (gap > gapsize) {
+                               gapsize = gap;
+                               gapstart = end;
+                               found = 1;
+                       }
+               }
+               if (start < last)
+                       last = start;
+       }
+
+       if (!found) {
+               gapstart = (end_pfn << PAGE_SHIFT) + 1024*1024;
+               printk(KERN_ERR "PCI: Warning: Cannot find a gap in the 32bit address range\n"
+                      KERN_ERR "PCI: Unassigned devices with 32bit resource registers may break!\n");
+       }
+
+       /*
+        * 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.
+        */
+       pci_mem_start = (gapstart + 0xfffff) & ~0xfffff;
+
+       printk(KERN_INFO "Allocating PCI resources starting at %lx (gap: %lx:%lx)\n",
+               pci_mem_start, gapstart, gapsize);
+}