[U-Boot] [PATCH v7 07/17] ARM: Put target PC for PSCI CPU_ON on per-CPU stack

[Wang Dongsheng]

> -----Original Message-----
> From: Jan Kiszka [mailto:jan.kiszka at siemens.com]
> Sent: Wednesday, May 13, 2015 3:31 PM
> To: Wang Dongsheng-B40534; U-Boot Mailing List; Tom Rini
> Cc: Marc Zyngier; Tom Warren; Paul Walmsley; Ian Campbell; Thierry Reding
> Subject: Re: [U-Boot] [PATCH v7 07/17] ARM: Put target PC for PSCI CPU_ON on
> per-CPU stack
> 
> On 2015-05-13 09:21, Wang Dongsheng wrote:
> >
> >
> >> -----Original Message-----
> >> From: U-Boot [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Jan
> >> Kiszka
> >> Sent: Tuesday, April 21, 2015 1:19 PM
> >> To: U-Boot Mailing List; Tom Rini
> >> Cc: Marc Zyngier; Tom Warren; Paul Walmsley; Ian Campbell; Thierry
> >> Reding
> >> Subject: [U-Boot] [PATCH v7 07/17] ARM: Put target PC for PSCI CPU_ON
> >> on per-CPU stack
> >>
> >> Use a per-CPU variable for saving the target PC during CPU_ON
> >> operations. This allows us to run this service independently on
> >> targets that have more than 2 cores and also core-local power control.
> >>
> >> CC: Marc Zyngier <marc.zyngier at arm.com>
> >> Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
> >> Reviewed-by: Tom Rini <trini at konsulko.com>
> >> Reviewed-by: Thierry Reding <treding at nvidia.com>
> >> Tested-by: Thierry Reding <treding at nvidia.com>
> >> Tested-by: Ian Campbell <ijc at hellion.org.uk>
> >> ---
> >>  arch/arm/cpu/armv7/psci.S       | 11 +++++------
> >>  arch/arm/cpu/armv7/sunxi/psci.S |  9 ++++++---
> >>  2 files changed, 11 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/arch/arm/cpu/armv7/psci.S b/arch/arm/cpu/armv7/psci.S
> >> index 18d85c4..87c0c0b 100644
> >> --- a/arch/arm/cpu/armv7/psci.S
> >> +++ b/arch/arm/cpu/armv7/psci.S
> >> @@ -17,6 +17,7 @@
> >>
> >>  #include <config.h>
> >>  #include <linux/linkage.h>
> >> +#include <asm/macro.h>
> >>  #include <asm/psci.h>
> >>
> >>  	.pushsection ._secure.text, "ax"
> >> @@ -202,6 +203,7 @@ ENTRY(psci_get_cpu_stack_top)
> >>  	add	r5, r5, #0x2000			@ Skip two pages
> >>  	lsr	r5, r5, #12			@ Align to start of page
> >>  	lsl	r5, r5, #12
> >> +	sub	r5, r5, #4			@ reserve 1 word for target PC
> >>  	sub	r0, r5, r0			@ here's our stack!
> >>
> >>  	bx	lr
> >> @@ -212,13 +214,10 @@ ENTRY(psci_cpu_entry)
> >>
> >>  	bl	_nonsec_init
> >>
> >> -	adr	r0, _psci_target_pc
> >> -	ldr	r0, [r0]
> >> +	bl	psci_get_cpu_id			@ CPU ID => r0
> >> +	bl	psci_get_cpu_stack_top		@ stack top => r0
> >> +	ldr	r0, [r0]			@ target PC at stack top
> >>  	b	_do_nonsec_entry
> >>  ENDPROC(psci_cpu_entry)
> >>
> >> -.globl _psci_target_pc
> >> -_psci_target_pc:
> >> -	.word	0
> >> -
> >>  	.popsection
> >> diff --git a/arch/arm/cpu/armv7/sunxi/psci.S
> >> b/arch/arm/cpu/armv7/sunxi/psci.S index dd583b2..7ec0500 100644
> >> --- a/arch/arm/cpu/armv7/sunxi/psci.S
> >> +++ b/arch/arm/cpu/armv7/sunxi/psci.S
> >> @@ -139,8 +139,11 @@ out:	mcr	p15, 0, r7, c1, c1, 0
> >>  	@ r2 = target PC
> >>  .globl	psci_cpu_on
> >>  psci_cpu_on:
> >> -	ldr	r0, =_psci_target_pc
> >> -	str	r2, [r0]
> >> +	push	{lr}
> >> +
> >> +	mov	r0, r1
> >> +	bl	psci_get_cpu_stack_top	@ get stack top of target CPU
> >> +	str	r2, [r0]		@ store target PC at stack top
> >
> > Base on target PC will be saved in stack. The cpu(r1) should be mask firstly.
> > Because r1 value is 0xf0x, and it is not what we expected cpu value(0x1
> or ...).
> > If not, the stack address is incorrect.
> >
> > When I develop LS1021a PSCI code, I found this issue. So I think sunxi
> > also has this issue.
> 
> IIRC, sunxi has no clusters != 0 so far, but you are right conceptually.

I don't know much about the sunxi platform. If I missed something please let me know.

The sunxi code also mask r1. So I guess the r1 the high of low-half word is also
not clear for sunxi platform.

        @ CPU mask
        and     r1, r1, #3      @ only care about first cluster
        mov     r4, #1
        lsl     r4, r4, r1

> We already mask elsewhere in that function, so the instruction should simply be
> moved up here.

Yes, psci_arch_init has mask for bootcpu, but there is should mask for cpu1 or... and
the stack is for target cpu. There is not for bootcpu stack.

Regards,
-Dongsheng