Subject: [PATCH] RBTX4927: linux-2.6.24-rc4 hang on boot

From: Frank Rowand <[email-masked]>
Date: Tue, 11 Dec 2007 10:16:27 -0500

In linux-2.6.24-rc4 the Toshiba RBTX4927 hangs on boot.

The cause is that plat_time_init() from arch/mips/tx4927/common/tx4927_setup.c
does not override the __weak plat_time_init() from arch/mips/kernel/time.c.
This is due to a compiler bug in gcc 4.1.1.  The bug is reported to not exist
in earlier versions of gcc, and to be fixed in 4.1.2.  The problem is that
the __weak plat_time_init() is empty and thus gets optimized out of
existence (thus the linker is never given the option to replace the
__weak function).

For more info on the gcc bug see

   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27781

The attached patch is one workaround.  Another possible workaround
would be to change the __weak plat_time_init() to be a non-empty
function.

Signed-off-by: Frank Rowand <[email-masked]>

---
 arch/mips/kernel/Makefile |    4 	4 +	0 -	0 !
 1 files changed, 4 insertions(+)

Index: linux-2.6.24-rc4/arch/mips/kernel/Makefile
===================================================================
--- linux-2.6.24-rc4.orig/arch/mips/kernel/Makefile
+++ linux-2.6.24-rc4/arch/mips/kernel/Makefile
@@ -83,6 +83,10 @@ obj-$(CONFIG_EARLY_PRINTK)	+= early_prin
 
 CFLAGS_cpu-bugs64.o	= $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
 
+# workaround for http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27781,
+# which impacts plat_time_init() for tx4927, gcc 4.1.1
+CFLAGS_time.o			+= -fno-unit-at-a-time
+
 obj-$(CONFIG_HAVE_STD_PC_SERIAL_PORT)	+= 8250-platform.o
 
 EXTRA_CFLAGS += -Werror

---

From: Ralf Baechle <[email-masked]>
Date: Fri, 14 Dec 2007 00:03:48 +0000

> existence (thus the linker is never given the option to replace the

You meant the call to plat_time_init() from time_init() gets optimized away.

> would be to change the __weak plat_time_init() to be a non-empty

The __weak definition of plat_time_init was only ever meant to be a
migration helper to keep platforms that don't have a plat_time_init
compiling.  A few greps says that all platforms now supply their own
plat_time_init() so the weak definition is no longer needed.  So I
instead delete it.

  Ralf