[U-Boot] [PATCH v2] powerpc/fsl: support low power boot for e500 and later

[Wang Dongsheng]

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?

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?

Regards,
-Dongsheng