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MIPS: Fix execution hazard during watchpoint register probe

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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@imgtec.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/5474/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2013-06-15 15:34:40 +00:00 committed by Ralf Baechle
parent c37441c127
commit c5e1503fd0
1 changed files with 8 additions and 0 deletions
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8
arch/mips/kernel/watch.c
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@ -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)