[PATCH] PPC64: close firmware stdin

We recently found a problem that was causing memory corruption during boot
on IBM POWER5 machines.  The problem was that the if you have a USB
keyboard and it is set to the input device for the firmware, it will still
be active when the kernel is started.  That means that the OHCI controller
has pointers to various memory areas that it polls for transfers to do. 
When we start using that same memory in the kernel, bad things can happen. 
(This isn't a problem on powermacs because the Apple OF implements a
"quiesce" call which turns off all the devices it is using.)

This patch fixes the problem by calling the Open Firmware "close" method
for the input device.  Stephen Rothwell and I have verified that doing this
fixes the problem on the POWER5 machine where we observed it.  I verified
that this patch doesn't cause any problems on powermacs.

I think this patch should go into 2.6.10 since it fixes a nasty memory
corruption bug that can cause rather subtle and hard-to-diagnose problems
during boot.  (The symptom on the POWER5 machine with the particular kernel
that we were using was that reading /proc/net/tcp would oops, due to one of
the pointers in tcp_ehash being corrupted.)
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ppc64/kernel/prom_init.c

@@ -1108,6 +1108,16 @@ static void __init prom_init_stdout(void)
 	}
 }
 
+static void __init prom_close_stdin(void)
+{
+	unsigned long offset = reloc_offset();
+	struct prom_t *_prom = PTRRELOC(&prom);
+	ihandle val;
+
+	if (prom_getprop(_prom->chosen, "stdin", &val, sizeof(val)) > 0)
+		call_prom("close", 1, 0, val);
+}
+
 static int __init prom_find_machine_type(void)
 {
 	unsigned long offset = reloc_offset();
@@ -1686,6 +1696,9 @@ unsigned long __init prom_init(unsigned long r3, unsigned long r4, unsigned long
        	prom_printf("copying OF device tree ...\n");
        	flatten_device_tree();
 
+	/* in case stdin is USB and still active on IBM machines... */
+	prom_close_stdin();
+
 	/*
 	 * Call OF "quiesce" method to shut down pending DMA's from
 	 * devices etc...