MIPS: asm: pgtable: Add c0 hazards on HTW start/stop sequences

When we use htw_{start,stop}() outside of htw_reset(), we need
to ensure that c0 changes have been propagated properly before
we attempt to continue with subsequence memory operations.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: <stable@vger.kernel.org> # 3.17+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9114/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index 62a6ba383d4f..45d7fd5e1466 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -99,16 +99,20 @@ extern void paging_init(void);
 
 #define htw_stop()                                                      \
 do {                                                                    \
-        if (cpu_has_htw)                                                \
+        if (cpu_has_htw) {                                              \
                 write_c0_pwctl(read_c0_pwctl() &                        \
                                ~(1 << MIPS_PWCTL_PWEN_SHIFT));          \
+                back_to_back_c0_hazard();                               \
+        }                                                               \
 } while(0)
 
 #define htw_start()                                                     \
 do {                                                                    \
-        if (cpu_has_htw)                                                \
+        if (cpu_has_htw) {                                              \
                 write_c0_pwctl(read_c0_pwctl() |                        \
                                (1 << MIPS_PWCTL_PWEN_SHIFT));           \
+                back_to_back_c0_hazard();                               \
+        }                                                               \
 } while(0)
 
 
@@ -116,9 +120,7 @@ do {									\
 do {                                                                    \
         if (cpu_has_htw) {                                              \
                 htw_stop();                                             \
-                back_to_back_c0_hazard();                               \
                 htw_start();                                            \
-                back_to_back_c0_hazard();                               \
         }                                                               \
 } while(0)