[PATCH 6/6] ARM: tegra114: add CPU hotplug support

[josephl@nvidia.com (Joseph Lo)]

On Thu, 2013-05-16 at 07:11 +0800, Stephen Warren wrote:
> On 05/15/2013 04:27 AM, Joseph Lo wrote:
> > The Tegra114 is a quad cores SoC. Each core can be hotplugged including
> > CPU0. The hotplug sequence can be controlled by setting event trigger in
> > flow controller. Then the flow controller will take care all the power
> > sequence that include CPU up and down.
> 
> > diff --git a/arch/arm/mach-tegra/Makefile b/arch/arm/mach-tegra/Makefile
> 
> > +obj-$(CONFIG_ARCH_TEGRA_114_SOC)	+= sleep-tegra30.o
> 
> CONFIG_ARCH_TEGRA_3x_SOC also adds that to obj-y. Will including it
> twice cause problems?
> 
Looks the compiler can take care of this. I didn't see any problem here.

> > diff --git a/arch/arm/mach-tegra/reset-handler.S b/arch/arm/mach-tegra/reset-handler.S
> 
> >   *	  CPU boot vector when restarting the a CPU following
> >   *	  an LP2 transition. Also branched to by LP0 and LP1 resume after
> >   *	  re-enabling sdram.
> > + *
> > + *	r6: SoC ID << 8
> 
> I meant to ask in patch 1: Perhaps the macro could do a >>8 so that code
> can compare directly against the SoC IDs instead of having to compare
> against shifted values.
> 
That's more easy to read the code indeed. Will do.

> > +	tegra_check_soc_id TEGRA114, TEGRA_APB_MISC_BASE, r6, r7
> > +	beq	no_cpu0_chk
> 
> Does that need a THUMB(it ...) added? Same elsewhere.
> 
Will double confirm again later.

> > +	cmp	r6, #(TEGRA114 <<8)
> 
> Needs a space after <<.
> 
> > diff --git a/arch/arm/mach-tegra/sleep-tegra30.S b/arch/arm/mach-tegra/sleep-tegra30.S
> 
> > @@ -45,12 +46,17 @@ ENDPROC(tegra30_hotplug_shutdown)
> >   * and powergates it -- flags (in R0) indicate the request type.
> >   * Must never be called for CPU 0.
> 
> That comment is wrong now, I think.
Only true for Tegra30 now. Will fix.

> 
> >  	tst	r0, #TEGRA30_POWER_HOTPLUG_SHUTDOWN
> > +	beq	flow_ctrl_setting_for_lp2
> > +
> > +	/* flow controller set up for hotplug */
> > +	mov	r3, #FLOW_CTRL_WAITEVENT		@ For hotplug
> > +	b	flow_ctrl_done
> > +flow_ctrl_setting_for_lp2:
> > +	/* flow controller set up for LP2 */
> > +	cmp	r10, #(TEGRA30 << 8)
> >  	moveq   r3, #FLOW_CTRL_WAIT_FOR_INTERRUPT	@ For LP2
> 
> Do you need e.g. "movne r3, #0" or similar here? Otherwise, I think r3
> ends up not being initialized.

Yes, I will add the code when I add LP2 support for Tegra114 later.
Currently the LP2 code flow only for Tegra30, so it's OK.

> 
> > -	movne	r3, #FLOW_CTRL_WAITEVENT		@ For hotplug
> > +flow_ctrl_done:
> > +	cmp	r10, #(TEGRA30 << 8)
> >  	str	r3, [r2]
> 
> I wonder whether creating a separate tegra114_cpu_shutdown() wouldn't be
> better, to avoid all the runtime conditional code.

I personally think the conditional code is OK. And the ARM CPU also had
hardware for branch detection also.

I had finished some further features for both Tegra30 and Tegra114. And
most of the code here can be shared each other at least until now I
could see. Once I see if there is a significant difference, then I would
prepare maintain the code separately too.