[PATCH] ppc64: DART iommu allocation fix

The current code allocating the DART has a couple of bugs, first
it's called on all machines including the ones who have no DART
(oops), and then it tries to access the device-tree using the
"of_chosen" pointer before it was initialized.

The enclosed patch fixes these.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ppc64/kernel/pmac_setup.c

@@ -447,6 +447,14 @@ static int __init pmac_probe(int platform)
 	if (platform != PLATFORM_POWERMAC)
 		return 0;
 
+	/*
+	 * On U3, the DART (iommu) must be allocated now since it
+	 * has an impact on htab_initialize (due to the large page it
+	 * occupies having to be broken up so the DART itself is not
+	 * part of the cacheable linar mapping
+	 */
+	alloc_u3_dart_table();
+
 	return 1;
 }
 

arch/ppc64/kernel/prom.c

@@ -83,6 +83,7 @@ extern unsigned long klimit;
 static int __initdata dt_root_addr_cells;
 static int __initdata dt_root_size_cells;
 static int __initdata iommu_is_off;
+int __initdata iommu_force_on;
 typedef u32 cell_t;
 
 #if 0
@@ -876,9 +877,11 @@ static int __init early_init_dt_scan_chosen(unsigned long node,
 		return 0;
 	systemcfg->platform = *prop;
 
-	/* check if iommu is forced off */
+	/* check if iommu is forced on or off */
 	if (get_flat_dt_prop(node, "linux,iommu-off", NULL) != NULL)
 		iommu_is_off = 1;
+	if (get_flat_dt_prop(node, "linux,iommu-force-on", NULL) != NULL)
+		iommu_force_on = 1;
 
 #ifdef CONFIG_PPC_PSERIES
 	/* To help early debugging via the front panel, we retreive a minimal

arch/ppc64/kernel/setup.c

@@ -406,16 +406,6 @@ void __init early_setup(unsigned long dt_ptr)
 
 	DBG("Found, Initializing memory management...\n");
 
-#ifdef CONFIG_U3_DART
-	/*
-	 * On U3, the DART (iommu) must be allocated now since it
-	 * has an impact on htab_initialize (due to the large page it
-	 * occupies having to be broken up so the DART itself is not
-	 * part of the cacheable linar mapping
-	 */
-	alloc_u3_dart_table();
-#endif /* CONFIG_U3_DART */
-
 	/*
 	 * Initialize stab / SLB management
 	 */

arch/ppc64/kernel/u3_iommu.c

@@ -47,6 +47,7 @@
 
 #include "pci.h"
 
+extern int iommu_force_on;
 
 /* physical base of DART registers */
 #define DART_BASE        0xf8033000UL
@@ -305,8 +306,7 @@ void __init alloc_u3_dart_table(void)
 	/* Only reserve DART space if machine has more than 2GB of RAM
 	 * or if requested with iommu=on on cmdline.
 	 */
-	if (lmb_end_of_DRAM() <= 0x80000000ull &&
-	    get_property(of_chosen, "linux,iommu-force-on", NULL) == NULL)
+	if (lmb_end_of_DRAM() <= 0x80000000ull && !iommu_force_on)
 		return;
 
 	/* 512 pages (2MB) is max DART tablesize. */