diff options
| author | Paul Walmsley <paul@pwsan.com> | 2013-07-30 12:38:45 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2013-07-31 11:12:59 +0100 |
| commit | 067e710b9a982a92cc8294d7fa0f1e924c65bba1 (patch) | |
| tree | e452b342468aae990be5bfc28062d082ab643622 /arch/arm | |
| parent | bed859c1eea89feaba2acbb57d967a6d6f68af09 (diff) | |
ARM: 7801/1: v6: prevent gcc 4.5 from reordering extended CP15 reads above is_smp() test
Commit 621a0147d5c921f4cc33636ccd0602ad5d7cbfbc ("ARM: 7757/1: mm:
don't flush icache in switch_mm with hardware broadcasting") breaks
the boot on OMAP2430SDP with omap2plus_defconfig. Tracked to an
undefined instruction abort from the CP15 read in
cache_ops_need_broadcast(). It turns out that gcc 4.5 reorders the
extended CP15 read above the is_smp() test. This breaks ARM1136 r0
cores, since they don't support several CP15 registers that later ARM
cores do. ARM1136JF-S TRM section 3.2.1 "Register allocation" has the
details.
So mark the extended CP15 read as clobbering memory, which prevents
the compiler from reordering it before the is_smp() test. Russell
states that the code generated from this approach is preferable to
marking the inline asm as volatile. Remove the existing condition
code clobber as it's obsolete, per Nico's post:
http://www.spinics.net/lists/arm-kernel/msg261208.html
This patch is a collaboration with Will Deacon and Russell King.
Comments from Paul Walmsley:
Russell, if you accept this one, might you also add Will's ack from the lists:
Comments from Paul Walmsley:
I'd also be obliged if you could add a Cc: line for Jonathan Austin, since he helped test:
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Tony Lindgren <tony@atomide.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Jonathan Austin <jonathan.austin@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
| -rw-r--r-- | arch/arm/include/asm/cputype.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h index 8c25dc4e9851..9672e978d50d 100644 --- a/arch/arm/include/asm/cputype.h +++ b/arch/arm/include/asm/cputype.h @@ -89,13 +89,18 @@ extern unsigned int processor_id; __val; \ }) +/* + * The memory clobber prevents gcc 4.5 from reordering the mrc before + * any is_smp() tests, which can cause undefined instruction aborts on + * ARM1136 r0 due to the missing extended CP15 registers. + */ #define read_cpuid_ext(ext_reg) \ ({ \ unsigned int __val; \ asm("mrc p15, 0, %0, c0, " ext_reg \ : "=r" (__val) \ : \ - : "cc"); \ + : "memory"); \ __val; \ }) |