linux-kernel - RE: [PATCH 2/7] pm: at91: pm_suspend: add the WFI support for ARMv7

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Message-ID: <B256D81BAE5131468A838E5D7A243641BFD35CC6@penmbx01>
Date:	Tue, 27 Jan 2015 04:44:02 +0000
From:	"Yang, Wenyou" <Wenyou.Yang@...el.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"Ferre, Nicolas" <Nicolas.FERRE@...el.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>
CC:	"sylvain.rochet@...secur.com" <sylvain.rochet@...secur.com>,
	"Vilchez, Patrice" <Patrice.VILCHEZ@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alexandre.belloni@...e-electrons.com" 
	<alexandre.belloni@...e-electrons.com>,
	"peda@...ntia.se" <peda@...ntia.se>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH 2/7] pm: at91: pm_suspend: add the WFI support for ARMv7

Hi Sergei,

Thank you for your review.

> -----Original Message-----
> From: Sergei Shtylyov [mailto:sergei.shtylyov@...entembedded.com]
> Sent: Monday, January 26, 2015 9:05 PM
> To: Yang, Wenyou; Ferre, Nicolas; linux@....linux.org.uk
> Cc: sylvain.rochet@...secur.com; Vilchez, Patrice; linux-kernel@...r.kernel.org;
> alexandre.belloni@...e-electrons.com; peda@...ntia.se; linux-arm-
> kernel@...ts.infradead.org
> Subject: Re: [PATCH 2/7] pm: at91: pm_suspend: add the WFI support for ARMv7
> 
> Hello.
> 
> On 1/26/2015 1:06 PM, Wenyou Yang wrote:
> 
> > Signed-off-by: Wenyou Yang <wenyou.yang@...el.com>
> > ---
> >   arch/arm/mach-at91/pm_suspend.S |   54
> ++++++++++++++++++++++++++++++++++++++-
> >   1 file changed, 53 insertions(+), 1 deletion(-)
> 
> > diff --git a/arch/arm/mach-at91/pm_suspend.S
> > b/arch/arm/mach-at91/pm_suspend.S index 122a3f1..e796722 100644
> > --- a/arch/arm/mach-at91/pm_suspend.S
> > +++ b/arch/arm/mach-at91/pm_suspend.S
> > @@ -53,6 +53,58 @@ mode	.req	r6
> >   	beq	1b
> >   	.endm
> >
> > +/*
> > + * Put the processor to enter the WFI state  */
> > +	.macro _do_wfi
> > +
> > +#if defined(CONFIG_CPU_V7)
> > +	/*
> > +	 * Execute an ISB instruction to flush the pipeline to ensure
> > +	 * that all of operations have beem completed.
> 
>     Been.
> 
> > +	 */
> > +	isb
> > +
> > +	/*
> > +	 * Execute an ISB instruction to ensure that all of the
> 
>     ISB again, while you're executing DSB/DMB?
>
Thank you for your pointing.
 
> > +	 * CP15 register changes have been committed.
> > +	 */
> > +	dsb
> > +	dmb
> > +
> > +	/* Disable the processor's clock */
> > +	mov	tmp1, #AT91_PMC_PCK
> 
>     What's 'tmp1'? Is that a register name?
Yes, a register name defined at the head of file.

> 
> > +	str	tmp1, [pmc, #AT91_PMC_SCDR]
> > +
> > +	/* Execute a WFI instruction */
> 
>     Self-obvious comment, I'd say...
> 
> > +	wfi	@ Wait For Interrupt
> > +
> > +	/*
> > +	 * CPU can specualatively prefetch the instructions
> 
>     Speculatively.
Thanks.
> 
> [...]
> 
> WBR, Sergei


Best Regards,
Wenyou Yang
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