MIPS: Allow R2 CPUs to turn off generation of 'ehb' instructions.

Some CPUs do not need ehb instructions after writing CP0 registers.
By allowing ehb generation to be overridden in
cpu-feature-overrides.h, we can save a few instructions in the TLB
handler hot paths.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 6 insertions, 1 deletions

diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index c0047f861337..1cba4b2ffd1e 100644
--- a/arch/mips/include/asm/cpu-features.h
+++ b/arch/mips/include/asm/cpu-features.h
@@ -147,6 +147,10 @@
 #define cpu_has_mips_r  (cpu_has_mips32r1 | cpu_has_mips32r2 | \
                          cpu_has_mips64r1 | cpu_has_mips64r2)
 
+#ifndef cpu_has_mips_r2_exec_hazard
+#define cpu_has_mips_r2_exec_hazard cpu_has_mips_r2
+#endif
+
 /*
  * MIPS32, MIPS64, VR5500, IDT32332, IDT32334 and maybe a few other
  * pre-MIPS32/MIPS53 processors have CLO, CLZ.  For 64-bit kernels
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index d9a18b2b7f82..0e34faaadb5c 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -259,7 +259,8 @@ static void __cpuinit build_tlb_write_entry(u32 **p, struct uasm_label **l,
         }
 
         if (cpu_has_mips_r2) {
-                uasm_i_ehb(p);
+                if (cpu_has_mips_r2_exec_hazard)
+                        uasm_i_ehb(p);
                 tlbw(p);
                 return;
         }