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.przyw...@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?
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...?
> _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.
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?
> + 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. What does the
(unsigned)-1 write to sysflags[1] do?
> +
> + /* 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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