While actually switching to non-secure state is one thing, the more important part of this process is to make sure that we still have full access to the interrupt controller (GIC). The GIC is fully aware of secure vs. non-secure state, some registers are banked, others may be configured to be accessible from secure state only. To be as generic as possible, we get the GIC memory mapped address based on the PERIPHBASE register. We check explicitly for ARM Cortex-A7 and A15 cores, assuming an A9 otherwise, as for those cores we know the offsets for the GIC CPU interface from the PERIPHBASE content. Other cores could be added as needed.
With the GIC accessible, we: a) allow private interrupts to be delivered to the core (GICD_IGROUPR0 = 0xFFFFFFFF) b) enable the CPU interface (GICC_CTLR[0] = 1) c) set the priority filter to allow non-secure interrupts (GICC_PMR = 0x80)
After having switched to non-secure state, we also enable the non-secure GIC CPU interface, since this register is banked.
Also we allow access to all coprocessor interfaces from non-secure state by writing the appropriate bits in the NSACR register.
For reasons obvious later we only use caller saved registers r0-r3.
Signed-off-by: Andre Przywara andre.przywara@linaro.org --- arch/arm/cpu/armv7/start.S | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+)
diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S index 7bfb19d..401b0eb 100644 --- a/arch/arm/cpu/armv7/start.S +++ b/arch/arm/cpu/armv7/start.S @@ -561,3 +561,48 @@ fiq:
#endif /* CONFIG_USE_IRQ */ #endif /* CONFIG_SPL_BUILD */ + +/* Routine to initialize GIC CPU interface and switch to nonsecure state. + */ +.globl _nonsec_gic_switch +_nonsec_gic_switch: + mrc p15, 4, r2, c15, c0, 0 @ r2 = PERIPHBASE + add r3, r2, #0x1000 @ GIC dist i/f offset + mvn r1, #0 + str r1, [r3, #0x80] @ allow private interrupts + + mrc p15, 0, r0, c0, c0, 0 @ MIDR + bfc r0, #16, #8 @ mask out variant, arch + bfc r0, #0, #4 @ and revision + movw r1, #0xc070 + movt r1, #0x4100 + cmp r0, r1 @ check for Cortex-A7 + orr r1, #0xf0 + cmpne r0, r1 @ check for Cortex-A15 + movne r1, #0x100 @ GIC CPU offset for A9 + moveq r1, #0x2000 @ GIC CPU offset for A15/A7 + add r3, r2, r1 @ r3 = GIC CPU i/f addr + + mov r1, #1 + str r1, [r3, #0] @ set GICC_CTLR[enable] + mov r1, #0x80 + str r1, [r3, #4] @ set GICC_PIMR[7] + + movw r1, #0x3fff + movt r1, #0x0006 + mcr p15, 0, r1, c1, c1, 2 @ NSACR = all copros to non-sec + + ldr r1, =_start + mcr p15, 0, r1, c12, c0, 0 @ set VBAR + mcr p15, 0, r1, c12, c0, 1 @ set MVBAR + + isb + smc #0 @ call into MONITOR mode + isb @ clobbers r0 and r1 + + mov r1, #1 + str r1, [r3, #0] @ set GICC_CTLR[enable] + add r2, r2, #0x1000 @ GIC dist i/f offset + str r1, [r2] @ allow private interrupts + + mov pc, lr