ARM: rockchip: ensure CPU to enter WFI/WFE state

The patch can ensure that v7_exit_coherency_flush() in rockchip_cpu_die()
executed in time.
The mdelay(1) has enough time to fix the problem of CPU offlining.
That's a workaround way in rockchip hotplug code,
At least, we haven't a better way to solve it. Who know,
that maybe fixed by chip (hardware) in the future.

Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

diff --git a/arch/arm/mach-rockchip/platsmp.c b/arch/arm/mach-rockchip/platsmp.c
index d1a5fec688872101a0e994bf0a96f9936c192b09..4187ac2b01b32a826d8bace9e91874ac15c5646f 100644 (file)
--- a/arch/arm/mach-rockchip/platsmp.c
+++ b/arch/arm/mach-rockchip/platsmp.c
@@ -321,6 +321,13 @@ static void __init rockchip_smp_prepare_cpus(unsigned int max_cpus)
 #ifdef CONFIG_HOTPLUG_CPU
 static int rockchip_cpu_kill(unsigned int cpu)
 {
+       /*
+        * We need a delay here to ensure that the dying CPU can finish
+        * executing v7_coherency_exit() and reach the WFI/WFE state
+        * prior to having the power domain disabled.
+        */
+       mdelay(1);
+
        pmu_set_power_domain(0 + cpu, false);
        return 1;
 }