linux-kernel - RE: [PATCH 1/7] ARM: imx: add timer stop flag to ARM power off state

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Date:   Tue, 9 Jan 2018 09:25:59 +0000
From:   Anson Huang <anson.huang@....com>
To:     Dong Aisheng <dongas86@...il.com>, Stefan Agner <stefan@...er.ch>
CC:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH 1/7] ARM: imx: add timer stop flag to ARM power off state



Best Regards!
Anson Huang


> -----Original Message-----
> From: Dong Aisheng [mailto:dongas86@...il.com]
> Sent: 2018-01-09 5:23 PM
> To: Stefan Agner <stefan@...er.ch>
> Cc: shawnguo@...nel.org; kernel@...gutronix.de; Fabio Estevam
> <fabio.estevam@....com>; robh+dt@...nel.org; mark.rutland@....com;
> linux-arm-kernel@...ts.infradead.org; devicetree@...r.kernel.org; linux-
> kernel@...r.kernel.org; Anson Huang <anson.huang@....com>; dl-linux-imx
> <linux-imx@....com>
> Subject: Re: [PATCH 1/7] ARM: imx: add timer stop flag to ARM power off state
> 
> On Tue, Jan 02, 2018 at 05:42:17PM +0100, Stefan Agner wrote:
> > When the CPU is in ARM power off state the ARM architected timers are
> > stopped. The flag is already present in the higher power WAIT mode.
> >
> > This allows to use the ARM generic timer on i.MX 6UL/6ULL SoC.
> > Without the flag the kernel freezes when the timer enters the first
> > time ARM power off mode.
> >
> > Cc: Anson Huang <anson.huang@....com>
> > Signed-off-by: Stefan Agner <stefan@...er.ch>
> 
> It seems ok at my side.
> Did you meet the real issue? If yes, how to reproduce?
> 
> Both mx6sx and mx6ul are using GPT which do not need that flag, suppose we
> should remove it, right?
> Anson can help confirm it.

For UP system like i.MX6SX, we do NOT enable "cortex-a9-twd-timer", so local
timer is NOT used, GPT is used instead, GPT's clock is NOT disabled when cpuidle,
so I think we should remove all these Timer stop flag for 6SX CPUIDLE.

Anson.

> 
> Regards
> Dong Aisheng
> 
> > ---
> >  arch/arm/mach-imx/cpuidle-imx6sx.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm/mach-imx/cpuidle-imx6sx.c
> > b/arch/arm/mach-imx/cpuidle-imx6sx.c
> > index c5a5c3a70ab1..d0f14b761ff7 100644
> > --- a/arch/arm/mach-imx/cpuidle-imx6sx.c
> > +++ b/arch/arm/mach-imx/cpuidle-imx6sx.c
> > @@ -89,6 +89,7 @@ static struct cpuidle_driver imx6sx_cpuidle_driver = {
> >  			 */
> >  			.exit_latency = 300,
> >  			.target_residency = 500,
> > +			.flags = CPUIDLE_FLAG_TIMER_STOP,
> >  			.enter = imx6sx_enter_wait,
> >  			.name = "LOW-POWER-IDLE",
> >  			.desc = "ARM power off",
> > --
> > 2.15.1
> >