[U-Boot] [PATCH v2 5/7] 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.

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/nonsec_virt.S    | 27 +++++++++++++++++++++++++++
 arch/arm/include/asm/armv7.h        |  1 +
 arch/arm/lib/virt-v7.c              | 19 ++++++++++++++++++-
 include/configs/vexpress_ca15_tc2.h |  3 +++
 4 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
index 656d99b..919f6e9 100644
--- a/arch/arm/cpu/armv7/nonsec_virt.S
+++ b/arch/arm/cpu/armv7/nonsec_virt.S
@@ -54,6 +54,33 @@ _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.
+ */
+.globl _smp_pen
+_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, [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
+	beq	waitloop		@ again (due to a spurious wakeup)
+	mov	pc, r0
+
 #define lo(x) ((x) & 0xFFFF)
 #define hi(x) ((x) >> 16)
 
diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
index 56d0dd0..04545b9 100644
--- a/arch/arm/include/asm/armv7.h
+++ b/arch/arm/include/asm/armv7.h
@@ -97,6 +97,7 @@ int armv7_switch_nonsec(void);
 
 /* defined in cpu/armv7/nonsec_virt.S */
 void _nonsec_init(void);
+void _smp_pen(void);
 #endif /* CONFIG_ARMV7_VIRT */
 
 #endif /* ! __ASSEMBLY__ */
diff --git a/arch/arm/lib/virt-v7.c b/arch/arm/lib/virt-v7.c
index 7876a77..6946e4d 100644
--- a/arch/arm/lib/virt-v7.c
+++ b/arch/arm/lib/virt-v7.c
@@ -95,6 +95,21 @@ static int get_gic_base_address(char **gicdptr)
 #endif
 }
 
+static void kick_secondary_cpus(char *gicdptr)
+{
+	unsigned int *sysflags;
+
+	sysflags = (void *)CONFIG_SYSFLAGS_ADDR;
+#ifdef CONFIG_SYSFLAGS_NEED_CLEAR_BITS
+	sysflags[1] = (unsigned)-1;
+#endif
+	*sysflags = (uintptr_t)_smp_pen;
+	dmb();
+
+	/* now kick all CPUs (expect this one) by writing to GICD_SGIR */
+	writel(1U << 24, &gicdptr[GICD_SGIR]);
+}
+
 int armv7_switch_nonsec(void)
 {
 	unsigned int reg, ret;
@@ -130,7 +145,9 @@ int armv7_switch_nonsec(void)
 	for (i = 0; i <= itlinesnr; i++)
 		writel((unsigned)-1, &gicdptr[GICD_IGROUPRn + 4 * i]);
 
-	/* call the non-sec switching code on this CPU */
+	kick_secondary_cpus(gicdptr);
+
+	/* call the non-sec switching code on this CPU also */
 	_nonsec_init();
 
 	return 0;
diff --git a/include/configs/vexpress_ca15_tc2.h b/include/configs/vexpress_ca15_tc2.h
index 4f425ac..ade9e5b 100644
--- a/include/configs/vexpress_ca15_tc2.h
+++ b/include/configs/vexpress_ca15_tc2.h
@@ -31,4 +31,7 @@
 #include "vexpress_common.h"
 #define CONFIG_BOOTP_VCI_STRING     "U-boot.armv7.vexpress_ca15x2_tc2"
 
+#define CONFIG_SYSFLAGS_ADDR 0x1c010030
+#define CONFIG_SYSFLAGS_NEED_CLEAR_BITS
+
 #endif
-- 
1.7.12.1