of/flattree: use callback to setup initrd from /chosen

At present, the fdt code sets the kernel-wide initrd_start and
initrd_end variables when parsing /chosen. On ARM, we only set these
once the bootmem has been reserved.

This change adds an arch hook to setup the initrd from the device
tree:

 void early_init_dt_setup_initrd_arch(unsigned long start,
				      unsigned long end);

The arch-specific code can then setup the initrd however it likes.

Compiled on powerpc, with CONFIG_BLK_DEV_INITRD=y and =n.
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/microblaze/kernel/prom.c

@@ -118,6 +118,16 @@ void __init early_init_devtree(void *params)
 	pr_debug(" <- early_init_devtree()\n");
 }
 
+#ifdef CONFIG_BLK_DEV_INITRD
+void __init early_init_dt_setup_initrd_arch(unsigned long start,
+		unsigned long end)
+{
+	initrd_start = (unsigned long)__va(start);
+	initrd_end = (unsigned long)__va(end);
+	initrd_below_start_ok = 1;
+}
+#endif
+
 /*******
  *
  * New implementation of the OF "find" APIs, return a refcounted

arch/powerpc/kernel/prom.c

@@ -510,6 +510,16 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 	memstart_addr = min((u64)memstart_addr, base);
 }
 
+#ifdef CONFIG_BLK_DEV_INITRD
+void __init early_init_dt_setup_initrd_arch(unsigned long start,
+		unsigned long end)
+{
+	initrd_start = (unsigned long)__va(start);
+	initrd_end = (unsigned long)__va(end);
+	initrd_below_start_ok = 1;
+}
+#endif
+
 static void __init early_reserve_mem(void)
 {
 	u64 base, size;

drivers/of/fdt.c

@@ -384,28 +384,23 @@ unsigned long __init unflatten_dt_node(unsigned long mem,
  */
 void __init early_init_dt_check_for_initrd(unsigned long node)
 {
-	unsigned long len;
+	unsigned long start, end, len;
 	u32 *prop;
 
 	pr_debug("Looking for initrd properties... ");
 
 	prop = of_get_flat_dt_prop(node, "linux,initrd-start", &len);
-	if (prop) {
-		initrd_start = (unsigned long)
-				__va(of_read_ulong(prop, len/4));
+	if (!prop)
+		return;
+	start = of_read_ulong(prop, len/4);
 
 	prop = of_get_flat_dt_prop(node, "linux,initrd-end", &len);
-		if (prop) {
-			initrd_end = (unsigned long)
-				__va(of_read_ulong(prop, len/4));
-			initrd_below_start_ok = 1;
-		} else {
-			initrd_start = 0;
-		}
-	}
+	if (!prop)
+		return;
+	end = of_read_ulong(prop, len/4);
 
-	pr_debug("initrd_start=0x%lx  initrd_end=0x%lx\n",
-		 initrd_start, initrd_end);
+	early_init_dt_setup_initrd_arch(start, end);
+	pr_debug("initrd_start=0x%lx  initrd_end=0x%lx\n", start, end);
 }
 #else
 inline void early_init_dt_check_for_initrd(unsigned long node)

include/linux/of_fdt.h

@@ -80,6 +80,16 @@ extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
 extern void early_init_dt_add_memory_arch(u64 base, u64 size);
 extern u64 dt_mem_next_cell(int s, u32 **cellp);
 
+/*
+ * If BLK_DEV_INITRD, the fdt early init code will call this function,
+ * to be provided by the arch code. start and end are specified as
+ * physical addresses.
+ */
+#ifdef CONFIG_BLK_DEV_INITRD
+extern void early_init_dt_setup_initrd_arch(unsigned long start,
+					    unsigned long end);
+#endif
+
 /* Early flat tree scan hooks */
 extern int early_init_dt_scan_root(unsigned long node, const char *uname,
 				   int depth, void *data);