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>

diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index c0047f8..1cba4b2 100644 (file)
--- 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 d9a18b2..0e34faa 100644 (file)
--- 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;
        }