[PATCH] ppc64: Fix booting on latest G5 models

[Benjamin Herrenschmidt]

Hi !

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 at kernel.crashing.org>

Index: linux-work/arch/ppc64/kernel/prom_init.c
===================================================================
--- linux-work.orig/arch/ppc64/kernel/prom_init.c	2005-05-02 10:48:08.000000000 +1000
+++ linux-work/arch/ppc64/kernel/prom_init.c	2005-05-23 08:23:33.000000000 +1000
@@ -1750,7 +1750,44 @@
 	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 at 0,f8000000"));
+	if ((long)u3 <= 0)
+		return;
+	i2c = call_prom("finddevice", 1, 1, ADDR("/u3 at 0,f8000000/i2c at f8001000"));
+	if ((long)i2c <= 0)
+		return;
+	mpic = call_prom("finddevice", 1, 1, ADDR("/u3 at 0,f8000000/mpic at 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 @@
 	}
 
 	/*
+	 * 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");
Index: linux-work/drivers/i2c/busses/i2c-keywest.c
===================================================================
--- linux-work.orig/drivers/i2c/busses/i2c-keywest.c	2005-05-02 10:48:09.000000000 +1000
+++ linux-work/drivers/i2c/busses/i2c-keywest.c	2005-05-21 08:38:40.000000000 +1000
@@ -516,6 +516,11 @@
 	u32 *psteps, *prate;
 	int rc;
 
+	if (np->n_intrs < 1 || np->n_addrs < 1) {
+		printk(KERN_ERR "%s: Missing interrupt or address !\n",
+		       np->full_name);
+		return -ENODEV;
+	}
 	if (pmac_low_i2c_lock(np))
 		return -ENODEV;