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Subject[PATCH 2/2] ARM: imx: cpuidle-imx6q: configure CCM to RUN mode when CPU is active
Date
There are two states in i.MX6Q cpuidle driver.
state[1]: ARM WFI mode
state[2]: i.MX6Q WAIT mode

Take i.MX6DL as example, think out such a case:
1. CPU0/1 both run at normal mode
2. On CPU0, `sleep 1` is executed. And there are no workload on CPU1.
3. CPU0 first runs into state[2] and 'wfi' instruction. Switched to use
GPT broadcast.
4. CPU1 runs into state[2] and configure CCM to WAIT MODE,
then 'wfi' instruction. Now arm_clk and local timer clock are
shutdown. Switched to use GPT broadcast
5. GPT broadcast timer interrupt comes to GPC/GIC, then CPU0 wakes up.
CPU0 switched to use arm local timer. CPU1 is still sleeping.
6. No workload on CPU0, CPU0 runs into state[1]. But CCM register
is still not restored to Normal RUN mode. 'wfi' + CCM WAIT will
cause arm_clk and arm core clk.
Now CPU0 stops, which is not correct.

So, need to make sure CCM configured to RUN mode when any cpu exit
state[2].

In this patch,
When CPU exits state[2], it configures CCM to RUN mode.
When all CPUs enters state[2], the last CPU needs to check
whether it's ok to configure CCM to WAIT mode or not.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---

V1:
This is to upstream patch:
http://git.freescale.com/git/cgit.cgi/imx/linux-imx.git/commit/?h=imx_4.9.11_1.0.0_ga&id=0d980646ee068b92db71fd5e4e4efcbc33749cbd

arch/arm/mach-imx/cpuidle-imx6q.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/arm/mach-imx/cpuidle-imx6q.c b/arch/arm/mach-imx/cpuidle-imx6q.c
index bfeb25aaf9a2..4d342e2fdfe6 100644
--- a/arch/arm/mach-imx/cpuidle-imx6q.c
+++ b/arch/arm/mach-imx/cpuidle-imx6q.c
@@ -30,6 +30,8 @@ static int imx6q_enter_wait(struct cpuidle_device *dev,
if (!spin_trylock(&master_lock))
goto idle;
imx6_set_lpm(WAIT_UNCLOCKED);
+ if (atomic_read(&master) != num_online_cpus())
+ imx6_set_lpm(WAIT_CLOCKED);
cpu_do_idle();
imx6_set_lpm(WAIT_CLOCKED);
spin_unlock(&master_lock);
@@ -41,6 +43,7 @@ static int imx6q_enter_wait(struct cpuidle_device *dev,
done:
atomic_dec(&master);

+ imx6_set_lpm(WAIT_CLOCKED);
return index;
}

--
2.14.1
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