[PATCH] ARM: omap2+: Revert omap-smp.c changes resetting CPU1 during boot

[Tony Lindgren]

* Tony Lindgren <tony at atomide.com> [170315 10:24]:
> * Tony Lindgren <tony at atomide.com> [170314 11:16]:
> > * Andrew F. Davis <afd at ti.com> [170314 10:59]:
> > Then onto the other related patches..
> > 
> > > We re-park cpu1 in bootROM in U-Boot already, in the U-Boot tree:
> > > arch/arm/mach-omap2/omap5/sec_entry_cpu1.S
> > 
> > OK good to hear.
> > 
> > > omap_smc_sec_cpu1() wakes up cpu1 into the function cpu1_entry(), this
> > > makes an SMC call to setup the core, then re-parks itself back in bootROM.
> > > Relevant code to run on cpu1:
> > > 
> > > > #define AUX_CORE_BOOT_0		0x48281800
> > > > #define AUX_CORE_BOOT_1		0x48281804
> > > > /* DRA7xx ROM code function "startup_BootSlave". This function is where CPU1
> > > >  * waits on WFE, polling on AUX_CORE_BOOT_x registers.
> > > >  * This address is same for J6 and J6 Eco.
> > > >  */
> > > > #define ROM_FXN_STARTUP_BOOTSLAVE     0x00038a64
> > > >
> > > > ldr	r4, =AUX_CORE_BOOT_0
> > > > mov	r5, #0x0
> > > > str	r5, [r4]
> > > > ldr	r4, =ROM_FXN_STARTUP_BOOTSLAVE
> > > > bx	r4	@ Jump back to ROM
> > > 
> > > We would have to do this in kernel. The issue I'm thinking we are going
> > > to hit is that the parking function in bootROM expects the MMU to be
> > > off. Although we don't really need to turn it off as long as we can
> > > identity map the bootROM area, the AUX_CORE_BOOT_0/1 space, and wherever
> > > we plan to exit the parking loop.
> > 
> > Would be good to hear what Russell thinks we should do here to park
> > CPU1.
> 
> How about we introduce smp_park_secondary()?
> 
> Then soft_restart() can call it between setup_mm_for_reboot()
> and cpu_proc_fin()?

Hmm that probably won't help as we'd have to still have a 1:1
mapping in cpu_die() to put CPU1 into WFI and release it in
smp_park_secondary() to the bootrom.

Anyways, I think in your use case it's the suspend/resume that needs
the state preserved for CPU1. Do you need kexec working in your use
case?

Regards,

Tony