From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 2/3] ARM: smp_scu: enable SCU standby support
Date: Mon, 21 Jul 2014 11:26:38 +0100 [thread overview]
Message-ID: <20140721102638.GE32578@arm.com> (raw)
In-Reply-To: <20140721092703.GL8537@dragon>
On Mon, Jul 21, 2014 at 05:27:04PM +0800, Shawn Guo wrote:
> On Mon, Jul 21, 2014 at 09:51:50AM +0100, Will Deacon wrote:
> > On Mon, Jul 21, 2014 at 08:45:54AM +0100, Shawn Guo wrote:
> > > With SCU standby enabled, SCU CLK will be turned off when all processors
> > > are in WFI mode. And the clock will be turned on when any processor
> > > leaves WFI mode.
> > >
> > > This behavior should be preferable in terms of power efficiency of
> > > system idle. So let's set the SCU standby bit to enable the support in
> > > function scu_enable().
> > >
> > > Signed-off-by: Shawn Guo <shawn.guo@freescale•com>
> > > ---
> > > arch/arm/kernel/smp_scu.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/arm/kernel/smp_scu.c b/arch/arm/kernel/smp_scu.c
> > > index c947508f84e6..9f29d167d02c 100644
> > > --- a/arch/arm/kernel/smp_scu.c
> > > +++ b/arch/arm/kernel/smp_scu.c
> > > @@ -18,6 +18,7 @@
> > >
> > > #define SCU_CTRL 0x00
> > > #define SCU_ENABLE (1 << 0)
> > > +#define SCU_STANDBY_ENABLE (1 << 5)
> > > #define SCU_CONFIG 0x04
> > > #define SCU_CPU_STATUS 0x08
> > > #define SCU_INVALIDATE 0x0c
> > > @@ -54,7 +55,7 @@ void scu_enable(void __iomem *scu_base)
> > > if (scu_ctrl & SCU_ENABLE)
> > > return;
> > >
> > > - scu_ctrl |= SCU_ENABLE;
> > > + scu_ctrl |= SCU_ENABLE | SCU_STANDBY_ENABLE;
> >
> > I don't think this bit exists on all revisions of the A9.
>
> Thanks for the info, Will. Is there any side-effect to write the
> standby bit on those revisions which do not define the bit?
The usual question - could the firmware enable this bit before Linux
starts? We already do a read/modify/write sequence here and are only
supposed to write the enable bit as the rest are implementation defined.
--
Catalin
next prev parent reply other threads:[~2014-07-21 10:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-21 7:45 [PATCH 0/3] Enable SCU standby support at core level Shawn Guo
2014-07-21 7:45 ` [PATCH 1/3] ARM: smp_scu: use macro for SCU enable bit Shawn Guo
2014-07-21 7:45 ` [PATCH 2/3] ARM: smp_scu: enable SCU standby support Shawn Guo
2014-07-21 8:51 ` Will Deacon
2014-07-21 9:27 ` Shawn Guo
2014-07-21 9:44 ` Will Deacon
2014-07-22 1:56 ` Shawn Guo
2014-07-21 10:26 ` Catalin Marinas [this message]
2014-07-22 2:09 ` Shawn Guo
2014-07-22 16:13 ` Catalin Marinas
2014-07-23 4:50 ` Shawn Guo
2014-07-23 16:45 ` Catalin Marinas
2014-07-24 8:49 ` Shawn Guo
2014-07-21 7:45 ` [PATCH 3/3] ARM: imx: remove SCU standby enable code Shawn Guo
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