[U-Boot] [PATCH 4/6] ARM: add SMP support for non-secure switch
TigerLiu at viatech.com.cn
TigerLiu at viatech.com.cn
Fri Jun 7 13:00:46 CEST 2013
Hi, experts:
Do these patch code exist in current u-boot code base?
Or, i have to download linaro version uboot?
Best wishes,
-----邮件原件-----
发件人: u-boot-bounces at lists.denx.de [mailto:u-boot-bounces at lists.denx.de] 代表 Andre Przywara
发送时间: 2013年5月31日 17:33
收件人: Christoffer Dall
抄送: geoff.levand at linaro.org; cdall at cs.columbia.edu; peter.maydell at linaro.org; agraf at suse.de; marc.zyngier at arm.com; trini at ti.com; kvmarm at lists.cs.columbia.edu; u-boot at lists.denx.de
主题: Re: [U-Boot] [PATCH 4/6] ARM: add SMP support for non-secure switch
On 05/31/2013 07:32 AM, Christoffer Dall wrote:
> On Mon, May 06, 2013 at 03:17:48PM +0200, Andre Przywara wrote:
>> Currently the non-secure switch is only done for the boot processor.
>> To later allow full SMP support, we have to switch all secondary
>> cores into non-secure state also.
>>
>> So we add an entry point for secondary CPUs coming out of low-power
>> state and make sure we put them into WFI again after having switched
>> to non-secure state.
>> For this we acknowledge and EOI the wake-up IPI, then go into WFI.
>> Once being kicked out of it later, we sanity check that the start
>> address has actually been changed (since another attempt to switch
>> to non-secure would block the core) and jump to the new address.
>>
>> The actual CPU kick is done by sending an inter-processor interrupt
>> via the GIC to all CPU interfaces except the requesting processor.
>> The secondary cores will then setup their respective GIC CPU
>> interface.
>>
>> The address secondary cores jump to is board specific, we provide
>> the value here for the Versatile Express board.
>>
>> Signed-off-by: Andre Przywara <andre.przywara at linaro.org>
>> ---
>> arch/arm/cpu/armv7/start.S | 27 ++++++++++++++++++++++++++-
>> arch/arm/include/asm/armv7.h | 1 +
>> arch/arm/lib/virt-v7.c | 9 ++++++++-
>> include/configs/vexpress_ca15_tc2.h | 1 +
>> 4 files changed, 36 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
>> index e63e892..02234c7 100644
>> --- a/arch/arm/cpu/armv7/start.S
>> +++ b/arch/arm/cpu/armv7/start.S
>> @@ -575,8 +575,19 @@ fiq:
>>
>> #ifdef CONFIG_ARMV7_VIRT
>> /* Routine to initialize GIC CPU interface and switch to nonsecure state.
>> + * Will be executed directly by secondary CPUs after coming out of
>> + * WFI, or can be called directly by C code for CPU 0.
>> + * Those two paths mandate to not use any stack and to only use registers
>> + * r0-r3 to comply with both the C ABI and the requirement of SMP startup
>> + * code.
>> */
>> .globl _nonsec_gic_switch
>> +.globl _smp_pen
>> +_smp_pen:
>> + mrs r0, cpsr
>> + orr r0, r0, #0xc0
>> + msr cpsr, r0 @ disable interrupts
>> + mov lr, #0 @ clear LR to mark secondary
>
> instead of this subtle abuse of lr, why not make this routine simply
> take a parameter?
How would this work if this is called out of SMP pen? Shall I rely on
the registers being zero, then? Not very stable, I guess.
I think this whole routine is special anyways, so I felt this "subtle
abuse" is OK.
An option would be to set r0 to 1 in the smp_pen path and pass 0 as the
first parameter when calling from C. But then I'd need to save this
value - possibly in the LR register ;-)
> I also slightly object against wrapping the _smp_pen around the
> _nonsec_gic_switch, I really think these are separate routines, where
> one can just call the other...?
The actual routine and the purpose are the same, just the entry and exit
code is different. So this fitted nicely in here. I can add a more
specific comment on the different entry points.
>> _nonsec_gic_switch:
>> mrc p15, 4, r2, c15, c0, 0 @ r2 = PERIPHBASE
>> add r3, r2, #0x1000 @ GIC dist i/f offset
>> @@ -617,5 +628,19 @@ _nonsec_gic_switch:
>> add r2, r2, #0x1000 @ GIC dist i/f offset
>> str r1, [r2] @ allow private interrupts
>>
>> - mov pc, lr
>> + cmp lr, #0
>> + movne pc, lr @ CPU 0 to return
>> + @ all others: go to sleep
>> +_ack_int:
>> + ldr r1, [r3, #0x0c] @ read GICD acknowledge
>> + str r1, [r3, #0x10] @ write GICD EOI
>> +
>> + adr r1, _smp_pen
>> +waitloop:
>> + wfi
>> + ldr r0, =CONFIG_SYSFLAGS_ADDR @ load start address
>> + ldr r0, [r0]
>> + cmp r0, r1 @ make sure we dont execute this code
>
> I think I raised this issue previously, but this code is in a core
> u-boot file, but I could imagine a board with a different crazy boot
> protocol that required you to check two different fields and jump
> through other hoops to wake up from the smp pen, so I really think the
> whole smp pen belongs in a board specific place.
Right, but I didn't want to do this prematurely without knowing what is
really needed. So my plan is to refactor this when adding Arndale
support. I think this is special anyways because of the SPL/non-SPL split.
And although you are right about it being a core u-boot file, this whole
code is protected by CONFIG_ARMV7_VIRT. For non-compliant boards one
would either not enable this or add support for it.
> Also, the boot-wrapper code used wfe instead, not sure if there are any
> users that just send an event and doesn't send an IPI?
Good point. Is WFE a complete superset of WFI? Then I could just change
this.
>> + beq waitloop @ again (due to a spurious wakeup)
>> + mov pc, r0
>> #endif /* CONFIG_ARMV7_VIRT */
>> diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
>> index 25afffe..296dc92 100644
>> --- a/arch/arm/include/asm/armv7.h
>> +++ b/arch/arm/include/asm/armv7.h
>> @@ -78,6 +78,7 @@ void v7_outer_cache_inval_range(u32 start, u32 end);
>> int armv7_switch_nonsec(void);
>>
>> /* defined in cpu/armv7/start.S */
>> +void _smp_pen(void);
>> void _nonsec_gic_switch(void);
>> #endif /* CONFIG_ARMV7_VIRT */
>>
>> diff --git a/arch/arm/lib/virt-v7.c b/arch/arm/lib/virt-v7.c
>> index 3a48aee..0248010 100644
>> --- a/arch/arm/lib/virt-v7.c
>> +++ b/arch/arm/lib/virt-v7.c
>> @@ -48,6 +48,7 @@ int armv7_switch_nonsec(void)
>> unsigned int reg;
>> volatile unsigned int *gicdptr;
>> unsigned itlinesnr, i;
>> + unsigned int *sysflags;
>>
>> /* check whether the CPU supports the security extensions */
>> asm("mrc p15, 0, %0, c0, c1, 1\n" : "=r"(reg));
>> @@ -106,7 +107,13 @@ int armv7_switch_nonsec(void)
>> for (i = 0; i <= itlinesnr; i++)
>> gicdptr[GICD_IGROUPR0 / 4 + i] = (unsigned)-1;
>>
>> - /* call the non-sec switching code on this CPU */
>> + /* now kick all CPUs (expect this one) by writing to GICD_SIGR */
>> + sysflags = (void *)CONFIG_SYSFLAGS_ADDR;
>> + sysflags[1] = (unsigned)-1;
>> + sysflags[0] = (uintptr_t)_smp_pen;
>> + gicdptr[GICD_SGIR / 4] = 1U << 24;
>
> here you definitely want a barrier to make sure you don't kick the cpus
> before the sysflags addresses have been written.
Right.
> What does the
> (unsigned)-1 write to sysflags[1] do?
This is either a ARM-TC or a VExpress "goodie": sysflags+0 is bit-set
only, sysflags+4 is bit-clear only. So to write arbitrary addresses in
here you better clear all bits first and then write in the value.
Cost me at least one day to find this out ;-)
So this should be guarded by VExpress specific defines, I guess. But
again didn't want to do this before support for a board with a different
behavior is actually implemented.
Regards,
Andre.
>> +
>> + /* call the non-sec switching code on this CPU also */
>> _nonsec_gic_switch();
>>
>> return 0;
>> diff --git a/include/configs/vexpress_ca15_tc2.h b/include/configs/vexpress_ca15_tc2.h
>> index 9e230ad..210a27c 100644
>> --- a/include/configs/vexpress_ca15_tc2.h
>> +++ b/include/configs/vexpress_ca15_tc2.h
>> @@ -32,5 +32,6 @@
>> #define CONFIG_BOOTP_VCI_STRING "U-boot.armv7.vexpress_ca15x2_tc2"
>>
>> #define CONFIG_SYS_CLK_FREQ 24000000
>> +#define CONFIG_SYSFLAGS_ADDR 0x1c010030
>>
>> #endif
>> --
>> 1.7.12.1
>>
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