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SubjectRe: [PATCH 1/7] ARM: imx: add timer stop flag to ARM power off state
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Am Dienstag, den 09.01.2018, 09:25 +0000 schrieb Anson Huang:
>
> Best Regards!
> Anson Huang
>
>
> > -----Original Message-----
> > From: Dong Aisheng [mailto:dongas86@gmail.com]
> > Sent: 2018-01-09 5:23 PM
> > To: Stefan Agner <stefan@agner.ch>
> > Cc: shawnguo@kernel.org; kernel@pengutronix.de; Fabio Estevam
> > <fabio.estevam@nxp.com>; robh+dt@kernel.org; mark.rutland@arm.com;
> > linux-arm-kernel@lists.infradead.org; devicetree@vger.kernel.org;
> > linux-
> > kernel@vger.kernel.org; Anson Huang <anson.huang@nxp.com>; dl-
> > linux-imx
> > <linux-imx@nxp.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@nxp.com>
> > > Signed-off-by: Stefan Agner <stefan@agner.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.

It's correct to set the flag even on UP systems, as the flag means the
CPU _local_ timer is stopped in this sleep mode. Also there are systems
out there which are using the TWD on UP, as it operates at a higher
frequency leading to better wakeup granularity.

Regards,
Lucas

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