[U-Boot] [PATCH v2] powerpc/fsl: support low power boot for e500 and later
Scott Wood
scottwood at freescale.com
Wed Aug 12 07:59:15 CEST 2015
On Wed, 2015-08-12 at 00:50 -0500, Wang Dongsheng-B40534 wrote:
> Hi Scott,
>
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Wednesday, August 12, 2015 1:18 PM
> > To: Wang Dongsheng-B40534
> > Cc: Sun York-R58495; u-boot at lists.denx.de
> > Subject: Re: [PATCH v2] powerpc/fsl: support low power boot for e500 and
> > later
> >
> > On Wed, 2015-08-12 at 00:15 -0500, Wang Dongsheng-B40534 wrote:
> > > Hi Scott,
> > >
> > > > -----Original Message-----
> > > > From: Wood Scott-B07421
> > > > Sent: Wednesday, August 12, 2015 12:55 PM
> > > > To: Wang Dongsheng-B40534
> > > > Cc: Sun York-R58495; u-boot at lists.denx.de
> > > > Subject: Re: [PATCH v2] powerpc/fsl: support low power boot for e500
> > > > and later
> > > >
> > > > On Tue, 2015-08-11 at 15:15 +0800, Dongsheng Wang wrote:
> > > > > From: Wang Dongsheng <dongsheng.wang at freescale.com>
> > > > >
> > > > > low power boot means u-boot will put non-boot cpus into a low
> > > > > power status. Non-boot cpus don't need any more spin wait. e500,
> > > > > e500v2 will going to DOZE status. e500mc, e5500, e6500 will going
> > > > > to PW10
> > state.
> > > > >
> > > > > e500/e500v2 will be kicked up by MPIC-IPI, e500mc later will be
> > > > > kicked up by doorbell.
> > > > >
> > > > > This feature tested on:
> > > > > POWER UP TEST:
> > > > > P1022DS(e500v2),96k times.
> > > > > P4080(e500mc), 110k times.
> > > > > T1024(e5500), 83k times.
> > > > > T4240(e6500), 150k times.
> > > > >
> > > > > CPU HOTPLUG TEST:
> > > > > P1022DS(e500v2),1.4 million times.
> > > > > P4080(e500mc), 1.8 million times.
> > > > > T1024(e5500), 1.3 million times.
> > > > > T4240(e6500), 1.1 million times.
> > > > >
> > > > > Signed-off-by: Wang Dongsheng <dongsheng.wang at freescale.com>
> > > > > ---
> > > > > *V2*
> > > > > Add:
> > > > > Add Config option to select Boot Method, Boot by SPIN TABLE or
> > > > > Boot By
> > > > > LOW POWER.
> > > > > The default boot method is SPIN TABLE.
> > > > >
> > > > > Modify:
> > > > > Rebase code to compatible with spin.
> > > > >
> > > > > Delete:
> > > > > Delete e6500rev2 PW20 state.
> > > > >
> > > > > The default boot method SPIN TABLE has tested on last kernel. The
> > > > > low power boot method need add a kernel patch to support. Now PPC
> > > > > smp cpu boot, cpu hotplug, sleep, and deep sleep patches is
> > > > > rebasing for upstream, after ppc smp cpu boot upstreamed i will
> > > > > commit a kernel patch to complete support low power boot method.
> > > > >
> > > > > diff --git a/arch/powerpc/cpu/mpc85xx/Kconfig
> > > > > b/arch/powerpc/cpu/mpc85xx/Kconfig
> > > > > index 3e8d0b1..9c81d97 100644
> > > > > --- a/arch/powerpc/cpu/mpc85xx/Kconfig
> > > > > +++ b/arch/powerpc/cpu/mpc85xx/Kconfig
> > > > > @@ -199,3 +199,26 @@ source "board/xes/xpedite550x/Kconfig"
> > > > > source "board/Arcturus/ucp1020/Kconfig"
> > > > >
> > > > > endmenu
> > > > > +
> > > > > +menu "mpc85xx CPU Boot Method"
> > > > > + depends on MPC85xx
> > > > > +
> > > > > +choice
> > > > > + prompt "Boot select"
> > > > > + default BOOT_BY_SPIN
> > > > > +
> > > > > +config BOOT_BY_SPIN
> > > > > + bool "Spin boot cpus"
> > > > > + help
> > > > > + Non-boot cpus will be falled in a spin state when U-boot
> > > > > + started up.
> > > > > +
> > > > > +config BOOT_BY_LOW_POWER
> > > > > + bool "Low power boot cpus"
> > > > > + help
> > > > > + Non-boot cpus will be falled in a low power state when U-
> > > > > boot
> > > > > + started up.
> > > > > +
> > > > > +endchoice
> > > >
> > > > I was going to say that this could be made dynamically configurable
> > > > by always putting the cores into low power mode, and then waking
> > > > them at bootm time if the spin table is chosen in the environment --
> > > > but if we can do that, we can also just leave the secondary cpus in
> > > > holdoff until bootm.
> > > >
> > > > At that point, we might as well just always use the spin table
> > > > because the time from bootm to the OS releasing the secondaries
> > > > should be
> > small.
> > > >
> > > Yes, if all of cpus will enable in kernel. But in some cases we do not
> > > enable all the CPU in the kernel, so we need to push them to low power
> > > state.
> >
> > If you don't plan to release a CPU in the OS, tell U-Boot to keep it
> > disabled.
>
> Such as bootargs "maxcpus", as your said if we tell u-boot to keep it
> disabled,
> I think that is a new work for spin table, that is your talked hold off
> state when
> u-boot boot up?
The spin table code itself shouldn't be affected much, but plat_mp_up() would
be called later (during bootm), and should check coredisr1 to skip any CPUs
that have been disabled by the user.
> You means drop this patch? And keep secondary cpus in hold off state when u-
> boot
> Boot up and if needed release them in bootm?
Yes.
-Scott
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