By default the trace broadcast is enabled on 44x systems.

To reduce power consumption when instruction tracing is not needed, disable trace broadcast.

Check External Debug Mode (EDM) bit to detect if it should be disabled or not.

Resetting system via a debugger will set the DBCR0[EDM] bit. Resetting via u-boot or OS will not.

Signed-off-by: Victor Gallardo vgallardo@apm.com --- arch/powerpc/cpu/ppc4xx/start.S | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/cpu/ppc4xx/start.S b/arch/powerpc/cpu/ppc4xx/start.S index 4bad32f..bac8681 100644 --- a/arch/powerpc/cpu/ppc4xx/start.S +++ b/arch/powerpc/cpu/ppc4xx/start.S @@ -340,6 +340,9 @@ _start_440: mfspr r1,SPRN_DBCR0 andis. r1, r1, 0x8000 /* test DBCR0[EDM] bit */ bne skip_debug_init /* if set, don't clear debug register */ + mfspr r1,SPRN_CCR0 + ori r1,r1,CCR0_DTB@l /* Disable Trace Broadcast */ + mtspr SPRN_CCR0,r1 mtspr SPRN_DBCR0,r0 mtspr SPRN_DBCR1,r0 mtspr SPRN_DBCR2,r0