ARM: pm: add function to set WFI low-power mode for SMP CPUs

Add a function to set the SCU low-power mode for SMP CPUs.  This
centralizes this functionality rather than having to expose the
SCU register definitions to each platform.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 23 insertions, 0 deletions

diff --git a/arch/arm/kernel/smp_scu.c b/arch/arm/kernel/smp_scu.c
index 9ab4149bd983..a1e757c3439b 100644
--- a/arch/arm/kernel/smp_scu.c
+++ b/arch/arm/kernel/smp_scu.c
@@ -50,3 +50,26 @@ void __init scu_enable(void __iomem *scu_base)
 	 */
 	flush_cache_all();
 }
+
+/*
+ * Set the executing CPUs power mode as defined.  This will be in
+ * preparation for it executing a WFI instruction.
+ *
+ * This function must be called with preemption disabled, and as it
+ * has the side effect of disabling coherency, caches must have been
+ * flushed.  Interrupts must also have been disabled.
+ */
+int scu_power_mode(void __iomem *scu_base, unsigned int mode)
+{
+	unsigned int val;
+	int cpu = smp_processor_id();
+
+	if (mode > 3 || mode == 1 || cpu > 3)
+		return -EINVAL;
+
+	val = __raw_readb(scu_base + SCU_CPU_STATUS + cpu) & ~0x03;
+	val |= mode;
+	__raw_writeb(val, scu_base + SCU_CPU_STATUS + cpu);
+
+	return 0;
+}