[U-Boot] [PATCH v4 6/8] ARM: add SMP support for non-secure switch

[Andre Przywara]

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,
so each supported board should implement smp_set_boot_cpu_addr().

Signed-off-by: Andre Przywara <andre.przywara at linaro.org>
---
 arch/arm/cpu/armv7/nonsec_virt.S | 22 ++++++++++++++++++++++
 arch/arm/cpu/armv7/virt-v7.c     | 16 +++++++++++++++-
 arch/arm/include/asm/armv7.h     |  1 +
 arch/arm/include/asm/gic.h       |  2 ++
 include/common.h                 |  2 ++
 5 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
index 81384df..a88fa6b 100644
--- a/arch/arm/cpu/armv7/nonsec_virt.S
+++ b/arch/arm/cpu/armv7/nonsec_virt.S
@@ -59,6 +59,28 @@ _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
diff --git a/arch/arm/cpu/armv7/virt-v7.c b/arch/arm/cpu/armv7/virt-v7.c
index 689023f..50f0a3a 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;
@@ -114,7 +125,10 @@ int armv7_switch_nonsec(void)
 	for (i = 0; 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 10ced11..06657fe 100644
--- a/arch/arm/include/asm/armv7.h
+++ b/arch/arm/include/asm/armv7.h
@@ -98,6 +98,7 @@ 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
diff --git a/include/common.h b/include/common.h
index e5220cf..05b30d7 100644
--- a/include/common.h
+++ b/include/common.h
@@ -642,6 +642,8 @@ void ft_pci_setup(void *blob, bd_t *bd);
 #endif
 #endif
 
+void smp_set_core_boot_addr(unsigned long addr, int corenr);
+void smp_kick_all_cpus(void);
 
 /* $(CPU)/serial.c */
 int	serial_init   (void);
-- 
1.7.12.1