linux-kernel - Re: [PATCH v2 08/44] cpuidle,imx6: Push RCU-idle into driver

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Date:   Mon, 19 Sep 2022 17:17:34 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
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Subject: Re: [PATCH v2 08/44] cpuidle,imx6: Push RCU-idle into driver

On Mon, Sep 19, 2022 at 05:03:04PM +0200, Peter Zijlstra wrote:
> On Mon, Sep 19, 2022 at 04:49:41PM +0200, Frederic Weisbecker wrote:
> > On Mon, Sep 19, 2022 at 11:59:47AM +0200, Peter Zijlstra wrote:
> > > Doing RCU-idle outside the driver, only to then temporarily enable it
> > > again, at least twice, before going idle is daft.
> > > 
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > > ---
> > >  arch/arm/mach-imx/cpuidle-imx6sx.c |    5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > --- a/arch/arm/mach-imx/cpuidle-imx6sx.c
> > > +++ b/arch/arm/mach-imx/cpuidle-imx6sx.c
> > > @@ -47,7 +47,9 @@ static int imx6sx_enter_wait(struct cpui
> > >  		cpu_pm_enter();
> > >  		cpu_cluster_pm_enter();
> > >  
> > > +		ct_idle_enter();
> > >  		cpu_suspend(0, imx6sx_idle_finish);
> > > +		ct_idle_exit();
> > >  
> > >  		cpu_cluster_pm_exit();
> > >  		cpu_pm_exit();
> > > @@ -87,7 +89,8 @@ static struct cpuidle_driver imx6sx_cpui
> > >  			 */
> > >  			.exit_latency = 300,
> > >  			.target_residency = 500,
> > > -			.flags = CPUIDLE_FLAG_TIMER_STOP,
> > > +			.flags = CPUIDLE_FLAG_TIMER_STOP |
> > > +				 CPUIDLE_FLAG_RCU_IDLE,
> > >  			.enter = imx6sx_enter_wait,
> > 
> > There is a second one below that also uses imx6sx_enter_wait.
> 
> Oh, above you mean; but only @index==2 gets us into the whole PM crud.
> @index==1 is fine afaict.

Ah ok, got it, hence why you didn't touch cpu_do_idle()...
May need to comment that somewhere...

Reviewed-by: Frederic Weisbecker <frederic@...nel.org>

Thanks!