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SubjectRE: [PATCH 2/7] pm: at91: pm_suspend: add the WFI support for ARMv7
Date
Hi Lorenzo,

Thank you for your review.

> -----Original Message-----
> From: Lorenzo Pieralisi [mailto:lorenzo.pieralisi@arm.com]
> Sent: Wednesday, January 28, 2015 7:26 PM
> To: Yang, Wenyou
> Cc: Ferre, Nicolas; linux@arm.linux.org.uk; linux-arm-kernel@lists.infradead.org;
> linux-kernel@vger.kernel.org; alexandre.belloni@free-electrons.com;
> sylvain.rochet@finsecur.com; peda@axentia.se; Vilchez, Patrice
> Subject: Re: [PATCH 2/7] pm: at91: pm_suspend: add the WFI support for ARMv7
>
> On Mon, Jan 26, 2015 at 10:06:01AM +0000, Wenyou Yang wrote:
>
> Commit log please.
Added in the v2.0

>
> > Signed-off-by: Wenyou Yang <wenyou.yang@atmel.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
>
> You will have to explain why you need this, really.
I don't understand your meaning.

>
> > +
> > +#if defined(CONFIG_CPU_V7)
> > + /*
> > + * Execute an ISB instruction to flush the pipeline to ensure
> > + * that all of operations have beem completed.
>
> s/beem/been
Thanks.

>
> > + */
> > + isb
> > +
> > + /*
> > + * Execute an ISB instruction to ensure that all of the
> > + * CP15 register changes have been committed.
> > + */
> > + dsb
>
> This is a dsb not an isb.
Changed in the v2.0

>
> > + dmb
>
> You have to explain why you need every single one of these barriers, otherwise I
> am NAKing this patch.
No need this one?

>
> > +
> > + /* Disable the processor's clock */
> > + mov tmp1, #AT91_PMC_PCK
> > + str tmp1, [pmc, #AT91_PMC_SCDR]
> > +
> > + /* Execute a WFI instruction */
> > + wfi @ Wait For Interrupt
>
> This one looks ok :)
>
> > +
> > + /*
> > + * CPU can specualatively prefetch the instructions
> > + * so add NOPs after WFI. Sixteen NOPs as Cortex-A5 pipeline.
>
> So what ? I suspect your issue is related to wfi completion on pending IRQ. I
> would like to know the details that describe the issue you are trying to solve here
> please.
Honestly, I referred to others, I will dig more, and test it.

>
> > + */
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > + nop
> > +#else
> > + mcr p15, 0, tmp1, c7, c0, 4
> > +#endif
>
> Tell us what's the problem you have to solve, first, then we will see how to fix it.
>
> Thanks,
> Lorenzo
>
> > +
> > + .endm
> > +
> > .text
> >
> > /*
> > @@ -181,7 +233,7 @@ sdr_sr_done:
> >
> > skip_disable_main_clock:
> > /* Wait for interrupt */
> > - mcr p15, 0, tmp1, c7, c0, 4
> > + _do_wfi
> >
> > tst mode, #AT91_PM_SLOW_CLOCK
> > beq skip_enable_main_clock
> > --
> > 1.7.9.5
> >
> > --
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> >

Best Regards,
Wenyou Yang


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