[MIPS] TX49 MFC0 bug workaround

If mfc0 $12 follows store and the mfc0 is last instruction of a
page and fetching the next instruction causes TLB miss, the result
of the mfc0 might wrongly contain EXL bit.

ERT-TX49H2-027, ERT-TX49H3-012, ERT-TX49HL3-006, ERT-TX49H4-008

Workaround: mask EXL bit of the result or place a nop before mfc0.  It
doesn't harm to always clear those bits, so we change the code to do so.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/include/asm-mips/interrupt.h b/include/asm-mips/interrupt.h
index 0da5818..7743487 100644 (file)
--- a/include/asm-mips/interrupt.h
+++ b/include/asm-mips/interrupt.h
@@ -47,6 +47,17 @@ static inline void local_irq_enable(void)
  * R4000/R4400 need three nops, the R4600 two nops and the R10000 needs
  * no nops at all.
  */
+/*
+ * For TX49, operating only IE bit is not enough.
+ *
+ * If mfc0 $12 follows store and the mfc0 is last instruction of a
+ * page and fetching the next instruction causes TLB miss, the result
+ * of the mfc0 might wrongly contain EXL bit.
+ *
+ * ERT-TX49H2-027, ERT-TX49H3-012, ERT-TX49HL3-006, ERT-TX49H4-008
+ *
+ * Workaround: mask EXL bit of the result or place a nop before mfc0.
+ */
 __asm__ (
        "       .macro  local_irq_disable\n"
        "       .set    push                                            \n"
@@ -55,8 +66,8 @@ __asm__ (
        "       di                                                      \n"
 #else
        "       mfc0    $1,$12                                          \n"
-       "       ori     $1,1                                            \n"
-       "       xori    $1,1                                            \n"
+       "       ori     $1,0x1f                                         \n"
+       "       xori    $1,0x1f                                         \n"
        "       .set    noreorder                                       \n"
        "       mtc0    $1,$12                                          \n"
 #endif
@@ -96,8 +107,8 @@ __asm__ (
        "       andi    \\result, 1                                     \n"
 #else
        "       mfc0    \\result, $12                                   \n"
-       "       ori     $1, \\result, 1                                 \n"
-       "       xori    $1, 1                                           \n"
+       "       ori     $1, \\result, 0x1f                              \n"
+       "       xori    $1, 0x1f                                        \n"
        "       .set    noreorder                                       \n"
        "       mtc0    $1, $12                                         \n"
 #endif
@@ -136,8 +147,8 @@ __asm__ (
 #else
        "       mfc0    $1, $12                                         \n"
        "       andi    \\flags, 1                                      \n"
-       "       ori     $1, 1                                           \n"
-       "       xori    $1, 1                                           \n"
+       "       ori     $1, 0x1f                                        \n"
+       "       xori    $1, 0x1f                                        \n"
        "       or      \\flags, $1                                     \n"
        "       mtc0    \\flags, $12                                    \n"
 #endif