MIPS: clear execution hazard after changing FTLB enable

On current P-series cores from Imagination the FTLB can be enabled or
disabled via a bit in the Config6 register, and an execution hazard is
created by changing the value of bit. The ftlb_disable function already
cleared that hazard but that does no good for other callers. Clear the
hazard in the set_ftlb_enable function that creates it, and only for the
cores where it applies.

This has the effect of reverting c982c6d6c48b ("MIPS: cpu-probe: Remove
cp0 hazard barrier when enabling the FTLB") which was incorrect.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: c982c6d6c48b ("MIPS: cpu-probe: Remove cp0 hazard barrier when enabling the FTLB")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14023/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 5069b5b..dd31754 100644 (file)
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -376,8 +376,6 @@ static int __init ftlb_disable(char *s)
                return 1;
        }
 
-       back_to_back_c0_hazard();
-
        config4 = read_c0_config4();
 
        /* Check that FTLB has been disabled */
@@ -560,6 +558,7 @@ static int set_ftlb_enable(struct cpuinfo_mips *c, enum ftlb_flags flags)
                }
 
                write_c0_config6(config);
+               back_to_back_c0_hazard();
                break;
        case CPU_I6400:
                /* There's no way to disable the FTLB */