linux-kernel - Re: [PATCH 2/2] ARM: imx: cpuidle-imx6q: configure CCM to RUN mode when CPU is active

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Message-ID: <20180124013505.GB9401@shlinux2>
Date:   Wed, 24 Jan 2018 09:35:05 +0800
From:   Peng Fan <van.freenix@...il.com>
To:     Peng Fan <peng.fan@....com>
Cc:     shawnguo@...nel.org, kernel@...gutronix.de, fabio.estevam@....com,
        aisheng.dong@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ARM: imx: cpuidle-imx6q: configure CCM to RUN mode
 when CPU is active

Hi,

For the two patch, ping..

On Sat, Dec 30, 2017 at 09:53:19PM +0800, Peng Fan wrote:
>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@....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
>

Thanks,
Peng.
--