Secondary cores should enter a low-power idle state when waiting to
be started. The "wfe" instruction causes a core to wait until an event
or interrupt arrives before continuing to the next instruction, and
the "sev" instruction sends a wakeup event to the other cores.

Add an "sev" (and a memory barrier) to bcm2836_boot_secondary, the
function that wakes the waiting cores during booting. This is required
if the secondary cores are sitting in "wfe", and harmless if not.

Signed-off-by: Phil Elwell <>
 arch/arm/mach-bcm/platsmp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/mach-bcm/platsmp.c b/arch/arm/mach-bcm/platsmp.c
index 3fa1a99..7811160 100644
--- a/arch/arm/mach-bcm/platsmp.c
+++ b/arch/arm/mach-bcm/platsmp.c
@@ -312,6 +312,9 @@ static int bcm2836_boot_secondary(unsigned int cpu, struct 
task_struct *idle)
               intc_base + LOCAL_MAILBOX3_SET0 + 16 * cpu);
+       dsb(sy);
+       sev();
        return 0;

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