[PATCH] ppc64: Fix booting on latest G5 models

The latest speedbumped Apple G5 models have a "bug" in the Open Firmware
device tree that lacks the proper interrupt routing information for the
northbridge i2c controller.  Apple's driver silently falls back into a
sub-optimal "polled" mode (heh, maybe they didn't even notice the bug
because of that :), our driver didn't properly check and crashes :(

This patch fixes our driver to not crash, and adds code to the
prom_init() OF trampoline code that detects the "bug" and adds the
missing information back for this chipset revision.  This fixes booting
and thermal control on these models.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 43 insertions, 1 deletions

diff --git a/arch/ppc64/kernel/prom_init.c b/arch/ppc64/kernel/prom_init.c
index 35ec42de962..6f79b7b9b44 100644
--- a/arch/ppc64/kernel/prom_init.c
+++ b/arch/ppc64/kernel/prom_init.c
@@ -1750,7 +1750,44 @@ static void __init flatten_device_tree(void)
         prom_printf("Device tree struct  0x%x -> 0x%x\n",
                     RELOC(dt_struct_start), RELOC(dt_struct_end));
 
- }
+}
+
+
+static void __init fixup_device_tree(void)
+{
+        unsigned long offset = reloc_offset();
+        phandle u3, i2c, mpic;
+        u32 u3_rev;
+        u32 interrupts[2];
+        u32 parent;
+
+        /* Some G5s have a missing interrupt definition, fix it up here */
+        u3 = call_prom("finddevice", 1, 1, ADDR("/u3@0,f8000000"));
+        if ((long)u3 <= 0)
+                return;
+        i2c = call_prom("finddevice", 1, 1, ADDR("/u3@0,f8000000/i2c@f8001000"));
+        if ((long)i2c <= 0)
+                return;
+        mpic = call_prom("finddevice", 1, 1, ADDR("/u3@0,f8000000/mpic@f8040000"));
+        if ((long)mpic <= 0)
+                return;
+
+        /* check if proper rev of u3 */
+        if (prom_getprop(u3, "device-rev", &u3_rev, sizeof(u3_rev)) <= 0)
+                return;
+        if (u3_rev != 0x35)
+                return;
+        /* does it need fixup ? */
+        if (prom_getproplen(i2c, "interrupts") > 0)
+                return;
+        /* interrupt on this revision of u3 is number 0 and level */
+        interrupts[0] = 0;
+        interrupts[1] = 1;
+        prom_setprop(i2c, "interrupts", &interrupts, sizeof(interrupts));
+        parent = (u32)mpic;
+        prom_setprop(i2c, "interrupt-parent", &parent, sizeof(parent));
+}
+
 
 static void __init prom_find_boot_cpu(void)
 {
@@ -1920,6 +1957,11 @@ unsigned long __init prom_init(unsigned long r3, unsigned long r4, unsigned long
         }
 
         /*
+         * Fixup any known bugs in the device-tree
+         */
+        fixup_device_tree();
+
+        /*
          * Now finally create the flattened device-tree
          */
         prom_printf("copying OF device tree ...\n");