Writing a value to a WatchLo* register creates an execution hazard, so if its value is then read before that hazard is cleared then said value may be invalid. The mips_probe_watch_registers function must therefore clear the execution hazard between setting the match bits in a WatchLo* register & reading the register back in order to check which are set. This fixes intermittent incorrect watchpoint register probing on some MIPS cores such as interAptiv & proAptiv. Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx> Reviewed-by: James Hogan <james.hogan@xxxxxxxxxx> Acked-by: Steven J. Hill <Steven.Hill@xxxxxxxxxx> --- arch/mips/kernel/watch.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/mips/kernel/watch.c b/arch/mips/kernel/watch.c index 7726f61..cbdc4de 100644 --- a/arch/mips/kernel/watch.c +++ b/arch/mips/kernel/watch.c @@ -111,6 +111,7 @@ __cpuinit void mips_probe_watch_registers(struct cpuinfo_mips *c) * disable the register. */ write_c0_watchlo0(7); + back_to_back_c0_hazard(); t = read_c0_watchlo0(); write_c0_watchlo0(0); c->watch_reg_masks[0] = t & 7; @@ -121,12 +122,14 @@ __cpuinit void mips_probe_watch_registers(struct cpuinfo_mips *c) c->watch_reg_use_cnt = 1; t = read_c0_watchhi0(); write_c0_watchhi0(t | 0xff8); + back_to_back_c0_hazard(); t = read_c0_watchhi0(); c->watch_reg_masks[0] |= (t & 0xff8); if ((t & 0x80000000) == 0) return; write_c0_watchlo1(7); + back_to_back_c0_hazard(); t = read_c0_watchlo1(); write_c0_watchlo1(0); c->watch_reg_masks[1] = t & 7; @@ -135,12 +138,14 @@ __cpuinit void mips_probe_watch_registers(struct cpuinfo_mips *c) c->watch_reg_use_cnt = 2; t = read_c0_watchhi1(); write_c0_watchhi1(t | 0xff8); + back_to_back_c0_hazard(); t = read_c0_watchhi1(); c->watch_reg_masks[1] |= (t & 0xff8); if ((t & 0x80000000) == 0) return; write_c0_watchlo2(7); + back_to_back_c0_hazard(); t = read_c0_watchlo2(); write_c0_watchlo2(0); c->watch_reg_masks[2] = t & 7; @@ -149,12 +154,14 @@ __cpuinit void mips_probe_watch_registers(struct cpuinfo_mips *c) c->watch_reg_use_cnt = 3; t = read_c0_watchhi2(); write_c0_watchhi2(t | 0xff8); + back_to_back_c0_hazard(); t = read_c0_watchhi2(); c->watch_reg_masks[2] |= (t & 0xff8); if ((t & 0x80000000) == 0) return; write_c0_watchlo3(7); + back_to_back_c0_hazard(); t = read_c0_watchlo3(); write_c0_watchlo3(0); c->watch_reg_masks[3] = t & 7; @@ -163,6 +170,7 @@ __cpuinit void mips_probe_watch_registers(struct cpuinfo_mips *c) c->watch_reg_use_cnt = 4; t = read_c0_watchhi3(); write_c0_watchhi3(t | 0xff8); + back_to_back_c0_hazard(); t = read_c0_watchhi3(); c->watch_reg_masks[3] |= (t & 0xff8); if ((t & 0x80000000) == 0) -- 1.8.3.1
