[POWERPC] Cleanup zImage handling of kernel entry with flat device tree

This makes 2 changes to clean up the flat device tree handling
logic in the zImage wrapper.

First, there were two callbacks from the dt_ops structure used for
producing a final flat tree to pass to the kerne: dt_ops.ft_pack()
which packed the flat tree (possibly a no-op) and dt_ops.ft_addr()
which retreived the address of the final blob.  Since they were only
ever called together, this patch combines the two into a single new
callback, dt_ops.finalize().  This new callback does whatever
platform-dependent things are necessary to produce a final flat device
tree blob, and returns the blob's addres.

Second, the current logic calls the kernel with a flat device tree if
one is build into the zImage wrapper, otherwise it boots the kernel
with a PROM pointer, expecting the kernel to copy the OF device tree
itself.  This approach precludes the possibility of the platform
wrapper code building a flat device tree from whatever
platform-specific information firmware provides.  Thus, this patch
takes the more sensible approach of invoking the kernel with a flat
tree if the dt_ops.finalize callback provides one (by whatever means).

So, the dt_ops.finalize callback can be NULL, or can be a function
which returns NULL.  In either case, the zImage wrapper logic assumes
that this is a platform with OF and invokes the kernel accordingly.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/boot/flatdevtree_misc.c

@@ -33,13 +33,9 @@ static int ft_setprop(const void *phandle, const char *propname,
 	return ft_set_prop(&cxt, phandle, propname, buf, buflen);
 }
 
-static void ft_pack(void)
+static unsigned long ft_finalize(void)
 {
 	ft_end_tree(&cxt);
-}
-
-static unsigned long ft_addr(void)
-{
 	return (unsigned long)cxt.bph;
 }
 
@@ -48,8 +44,7 @@ int ft_init(void *dt_blob, unsigned int max_size, unsigned int max_find_device)
 	dt_ops.finddevice = ft_finddevice;
 	dt_ops.getprop = ft_getprop;
 	dt_ops.setprop = ft_setprop;
-	dt_ops.ft_pack = ft_pack;
-	dt_ops.ft_addr = ft_addr;
+	dt_ops.finalize = ft_finalize;
 
 	return ft_open(&cxt, dt_blob, max_size, max_find_device,
 			platform_ops.realloc);

arch/powerpc/boot/main.c

@@ -298,6 +298,7 @@ void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
 {
 	kernel_entry_t kentry;
 	char cmdline[COMMAND_LINE_SIZE];
+	unsigned long ft_addr = 0;
 
 	memset(__bss_start, 0, _end - __bss_start);
 	memset(&platform_ops, 0, sizeof(platform_ops));
@@ -328,14 +329,20 @@ void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
 		set_cmdline(cmdline);
 	}
 
+	printf("Finalizing device tree...");
+	if (dt_ops.finalize)
+		ft_addr = dt_ops.finalize();
+	if (ft_addr)
+		printf(" flat tree at 0x%lx\n\r", ft_addr);
+	else
+		printf(" using OF tree (promptr=%p)\n\r", promptr);
+
 	if (console_ops.close)
 		console_ops.close();
 
 	kentry = (kernel_entry_t) vmlinux.addr;
-	if (_dtb_end > _dtb_start) {
-		dt_ops.ft_pack();
-		kentry(dt_ops.ft_addr(), 0, NULL);
-	}
+	if (ft_addr)
+		kentry(ft_addr, 0, NULL);
 	else
 		/* XXX initrd addr/size should be passed in properties */
 		kentry(initrd.addr, initrd.size, promptr);

arch/powerpc/boot/ops.h

@@ -35,8 +35,7 @@ struct dt_ops {
 			const int buflen);
 	int	(*setprop)(const void *phandle, const char *name,
 			const void *buf, const int buflen);
-	void	(*ft_pack)(void);
-	unsigned long (*ft_addr)(void);
+	unsigned long (*finalize)(void);
 };
 extern struct dt_ops dt_ops;