On Mon, 2015-09-14 at 08:21 +0200, Christophe Leroy wrote: > 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
Instead couldn't you use the generic memset at label 2: and patch the "bne 2f"? -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
