[PATCH v5 4/4] Loongson-2F: Fixup of problems introduced by -mfix-loongson2f-jump

[Wu Zhangjin <wuzhangjin@gmail.com>]

From: Wu Zhangjin <wuzhangjin@gmail.com>

Changes from old revisions:

  o Incorporated with the feedbacks from Ralf Baechle and used the
  option CONFIG_CPU_JUMP_WORKAROUNDS introduced by "Loongson: Add
  CPU_LOONGSON2F_WORKAROUNDS".

The -mfix-loongson2f-jump option provided by the latest binutils(in the cvs
repository) have fixed the Out-of-order Issue of Loongson-2F described in
Chapter 15 of "Loongson2F User Manual"[1,2], but introduced some problems.

The option changes all of the jumping target to "addr & 0xcfffffff" through the
at($1) register, but for the REBOOT address of loongson-2F: 0xbfc00000, this is
totally wrong, so, this patch try to avoid the problem via telling the
assembler not to use at($1) register.

[1] Loongson2F User Manual(Chinese Version)
http://www.loongson.cn/uploadfile/file/200808211
[2] English Version of Chapter 15:
http://groups.google.com.hk/group/loongson-dev/msg/e0d2e220958f10a6?dmode=source

Reported-and-tested-by: Liu Shiwei <liushiwei@gmail.com>
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
 arch/mips/loongson/common/reset.c |   20 +++++++++++++++++++-
 1 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/arch/mips/loongson/common/reset.c 
b/arch/mips/loongson/common/reset.c
index 4bd9c18..9e10d62 100644
--- a/arch/mips/loongson/common/reset.c
+++ b/arch/mips/loongson/common/reset.c
@@ -16,13 +16,31 @@
 
 #include <loongson.h>
 
+static inline void loongson_reboot(void)
+{
+#ifndef CONFIG_CPU_JUMP_WORKAROUNDS
+       ((void (*)(void))ioremap_nocache(LOONGSON_BOOT_BASE, 4)) ();
+#else
+       void (*func)(void);
+
+       func = (void *)ioremap_nocache(LOONGSON_BOOT_BASE, 4);
+
+       __asm__ __volatile__(
+       "       .set    noat                                            \n"
+       "       jr      %[func]                                         \n"
+       "       .set    at                                              \n"
+       : /* No outputs */
+       : [func] "r" (func));
+#endif
+}
+
 static void loongson_restart(char *command)
 {
        /* do preparation for reboot */
        mach_prepare_reboot();
 
        /* reboot via jumping to boot base address */
-       ((void (*)(void))ioremap_nocache(LOONGSON_BOOT_BASE, 4)) ();
+       loongson_reboot();
 }
 
 static void loongson_poweroff(void)
-- 
1.7.0.1