linux-kernel - Re: [PATCH] ARM: exynos4212: hotplug: Fix CPU idle clock down after CPU1 off

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Message-id: <1401453990.11651.2.camel@AMDC1943>
Date:	Fri, 30 May 2014 14:46:30 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Tomasz Figa <tomasz.figa@...il.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene.kim@...sung.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>
Subject: Re: [PATCH] ARM: exynos4212: hotplug: Fix CPU idle clock down after
 CPU1 off

On pią, 2014-05-30 at 13:50 +0200, Tomasz Figa wrote:
> Hi Krzysztof,
> 
> On 13.05.2014 16:12, Krzysztof Kozlowski wrote:
> > On Exynos4212 USE_DELAYED_RESET_ASSERTION must be set in
> > ARM_CORE1_OPTION register during CPU power down. This is the proper way
> > of powering down CPU. Additionally without this the CPU clock down won't
> > work after powering down CPU1 and CPU will work at full frequency chosen
> > by CPUfreq governor.
> > 
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> > ---
> >  arch/arm/mach-exynos/hotplug.c  | 28 +++++++++++++++++++++++++---
> >  arch/arm/mach-exynos/regs-pmu.h |  2 ++
> >  2 files changed, 27 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm/mach-exynos/hotplug.c b/arch/arm/mach-exynos/hotplug.c
> > index 5eead530c6f8..59b813e74558 100644
> > --- a/arch/arm/mach-exynos/hotplug.c
> > +++ b/arch/arm/mach-exynos/hotplug.c
> > @@ -74,7 +74,7 @@ static inline void cpu_enter_lowpower_a15(void)
> >  	dsb();
> >  }
> >  
> > -static inline void cpu_leave_lowpower(void)
> > +static inline void cpu_leave_lowpower(unsigned int cpu)
> >  {
> >  	unsigned int v;
> >  
> > @@ -88,6 +88,14 @@ static inline void cpu_leave_lowpower(void)
> >  	  : "=&r" (v)
> >  	  : "Ir" (CR_C), "Ir" (0x40)
> >  	  : "cc");
> > +
> > +	if (cpu == 1 && soc_is_exynos4212()) {
> 
> AFAIK this is needed not only on Exynos4x12, but at least also on 4412.
> Also I don't think the (cpu == 1) condition is necessary. See below.

I'll test it on Exynos4412.

> 
> > +		unsigned int tmp;
> > +
> > +		tmp = __raw_readl(S5P_ARM_CORE1_OPTION);
> > +		tmp &= ~(S5P_USE_DELAYED_RESET_ASSERTION);
> > +		__raw_writel(tmp, S5P_ARM_CORE1_OPTION);
> > +	}
> >  }
> >  
> >  static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
> > @@ -95,8 +103,22 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
> >  	for (;;) {
> >  
> >  		/* make cpu1 to be turned off at next WFI command */
> > -		if (cpu == 1)
> > +		if (cpu == 1) {
> 
> I think this patch should be rebased on top of my "[PATCH] ARM: EXYNOS:
> Fix core ID used by platsmp and hotplug code". Then instead of if (cpu
> == 1) you would just use EXYNOS_ARM_CORE_OPTION(core_id).
> 
> Also same comment as above, I believe this is also needed on Exynos4412.

Probably your patch needs rebasing too. I couldn't apply (cleanly) on
current Linus' tree and on Kukjin's for-next. What are the requirements
for it?

Best regards,
Krzysztof


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