ARM: add SMP support for non-secure switch

Currently the non-secure switch is only done for the boot processor.
To enable 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.
While this approach is pretty universal across several ARMv7 boards,
we make this function weak in case someone needs to tweak this for
a specific board.

The way of setting the secondary's start address is board specific,
but mostly different only in the actual SMP pen address, so we also
provide a weak default implementation and just depend on the proper
address to be set in the config file.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>

4 files changed, 53 insertions, 1 deletions

diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
index 3dd60b7..cbee8f7 100644
--- a/arch/arm/cpu/armv7/nonsec_virt.S
+++ b/arch/arm/cpu/armv7/nonsec_virt.S
@@ -58,6 +58,28 @@ _secure_monitor:
 	movs	pc, lr				@ return to non-secure SVC
 
 /*
+ * Secondary CPUs start here and call the code for the core specific parts
+ * of the non-secure and HYP mode transition. The GIC distributor specific
+ * code has already been executed by a C function before.
+ * Then they go back to wfi and wait to be woken up by the kernel again.
+ */
+ENTRY(_smp_pen)
+	mrs	r0, cpsr
+	orr	r0, r0, #0xc0
+	msr	cpsr, r0			@ disable interrupts
+	ldr	r1, =_start
+	mcr	p15, 0, r1, c12, c0, 0		@ set VBAR
+
+	bl	_nonsec_init
+
+	ldr	r1, [r0, #GICC_IAR]		@ acknowledge IPI
+	str	r1, [r0, #GICC_EOIR]		@ signal end of interrupt
+
+	adr	r0, _smp_pen			@ do not use this address again
+	b	smp_waitloop			@ wait for IPIs, board specific
+ENDPROC(_smp_pen)
+
+/*
  * Switch a core to non-secure state.
  *
  *  1. initialize the GIC per-core interface
@@ -138,3 +160,16 @@ ENTRY(_nonsec_init)
 
 	bx	lr
 ENDPROC(_nonsec_init)
+
+#ifdef CONFIG_SMP_PEN_ADDR
+/* void __weak smp_waitloop(unsigned previous_address); */
+ENTRY(smp_waitloop)
+	wfi
+	ldr	r1, =CONFIG_SMP_PEN_ADDR	@ load start address
+	ldr	r1, [r1]
+	cmp	r0, r1			@ make sure we dont execute this code
+	beq	smp_waitloop		@ again (due to a spurious wakeup)
+	mov	pc, r1
+ENDPROC(smp_waitloop)
+.weak smp_waitloop
+#endif
diff --git a/arch/arm/cpu/armv7/virt-v7.c b/arch/arm/cpu/armv7/virt-v7.c
index 068ac85..a0b8742 100644
--- a/arch/arm/cpu/armv7/virt-v7.c
+++ b/arch/arm/cpu/armv7/virt-v7.c
@@ -79,6 +79,17 @@ static unsigned long get_gicd_base_address(void)
 #endif
 }
 
+static void kick_secondary_cpus_gic(unsigned long gicdaddr)
+{
+	/* kick all CPUs (except this one) by writing to GICD_SGIR */
+	writel(1U << 24, gicdaddr + GICD_SGIR);
+}
+
+void __weak smp_kick_all_cpus(void)
+{
+	kick_secondary_cpus_gic(gic_dist_addr);
+}
+
 int armv7_switch_nonsec(void)
 {
 	unsigned int reg;
@@ -115,7 +126,10 @@ int armv7_switch_nonsec(void)
 	for (i = 1; i <= itlinesnr; i++)
 		writel((unsigned)-1, gic_dist_addr + GICD_IGROUPRn + 4 * i);
 
-	/* call the non-sec switching code on this CPU */
+	smp_set_core_boot_addr((unsigned long)_smp_pen, -1);
+	smp_kick_all_cpus();
+
+	/* call the non-sec switching code on this CPU also */
 	_nonsec_init();
 
 	return 0;
diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
index b352d43..2efd4bc 100644
--- a/arch/arm/include/asm/armv7.h
+++ b/arch/arm/include/asm/armv7.h
@@ -82,6 +82,7 @@ int armv7_switch_nonsec(void);
 
 /* defined in assembly file */
 unsigned int _nonsec_init(void);
+void _smp_pen(void);
 #endif /* CONFIG_ARMV7_NONSEC */
 
 #endif /* ! __ASSEMBLY__ */
diff --git a/arch/arm/include/asm/gic.h b/arch/arm/include/asm/gic.h
index c2b1e28..a0891cc 100644
--- a/arch/arm/include/asm/gic.h
+++ b/arch/arm/include/asm/gic.h
@@ -13,5 +13,7 @@
 #define GIC_CPU_OFFSET_A15	0x2000
 #define GICC_CTLR		0x0000
 #define GICC_PMR		0x0004
+#define GICC_IAR		0x000C
+#define GICC_EOIR		0x0010
 
 #endif