memset() uses instruction dcbz to speed up clearing by not wasting time
loading cache line with data that will be overwritten.
Some platform like mpc52xx do no have cache active at startup and
can therefore not use memset(). Allthough no part of the code
explicitly uses memset(), GCC may makes calls to it.
This patch modifies memset() such that at startup, memset()
unconditionally jumps to simple_memset() which doesn't use
the dcbz instruction.
Once the initial MMU is set up, in machine_init() we patch memset()
by replacing this inconditional jump by a NOP
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
This patch goes on to of [v3] powerpc32: memcpy: only use dcbz once cache
is enabled
Changes in v2:
was part of [v2] powerpc32: memcpy/memset: only use dcbz once cache is
enabled
changes in v3:
Not using anymore feature-fixups
Handling of memcpy() and memset() split in two patches
arch/powerpc/kernel/setup_32.c | 1 +
arch/powerpc/lib/copy_32.S | 15 +++++++++++++++
2 files changed, 16 insertions(+)
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index 362495f..345ec3a 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -124,6 +124,7 @@ notrace void __init machine_init(u64 dt_ptr)
udbg_early_init();
patch_instruction((unsigned int *)&memcpy, PPC_INST_NOP);
+ patch_instruction((unsigned int *)&memset, PPC_INST_NOP);
/* Do some early initialization based on the flat device tree */
early_init_devtree(__va(dt_ptr));
diff --git a/arch/powerpc/lib/copy_32.S b/arch/powerpc/lib/copy_32.S
index da5847d..68a59d4 100644
--- a/arch/powerpc/lib/copy_32.S
+++ b/arch/powerpc/lib/copy_32.S
@@ -73,8 +73,13 @@ CACHELINE_MASK = (L1_CACHE_BYTES-1)
* Use dcbz on the complete cache lines in the destination
* to set them to zero. This requires that the destination
* area is cacheable. -- paulus
+ *
+ * During early init, cache might not be active yet, so dcbz cannot be
used.
+ * We therefore jump to simple_memset which doesn't use dcbz. This jump is
+ * replaced by a nop once cache is active. This is done in machine_init()
*/
_GLOBAL(memset)
+ b simple_memset
rlwimi r4,r4,8,16,23
rlwimi r4,r4,16,0,15
@@ -122,6 +127,16 @@ _GLOBAL(memset)
bdnz 8b
blr
+/* Simple version of memset used during early boot until cache is enabled
*/
+simple_memset:
+ cmplwi cr0,r5,0
+ addi r6,r3,-1
+ beqlr
+ mtctr r5
+1: stbu r4,1(r6)
+ bdnz 1b
+ blr
