qemu/arm: Add definition for the MPS2_AN500 machine.

This commit introduces a new target for the QEMU port called
"MPS2_AN500", an ARMv7-M machine with a Cortex-M7 CPU and
single-/double-precision floating point unit.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

ports/qemu/README.md

@@ -59,6 +59,7 @@ Available boards are:
 | ----------------- | ------------ | ------------------------ |
 | `MICROBIT`        | `arm`        | `microbit`               |
 | `MPS2_AN385`      | `arm`        | `mps2-an385`             |
+| `MPS2_AN500`      | `arm`        | `mps2-an500`             |
 | `NETDUINO2`       | `arm`        | `netduino2`              |
 | `SABRELITE`       | `arm`        | `sabrelite`              |
 | `VIRT_RV32`       | `riscv32`    | `virt`                   |

ports/qemu/boards/MPS2_AN500/mpconfigboard.mk

@@ -0,0 +1,15 @@
+QEMU_ARCH = arm
+QEMU_MACHINE = mps2-an500
+
+CFLAGS += -mthumb -mcpu=cortex-m7 -mfloat-abi=hard -mfpu=fpv5-d16
+CFLAGS += -DQEMU_SOC_MPS2
+CFLAGS += -DMICROPY_HW_MCU_NAME='"Cortex-M7"'
+
+LDSCRIPT = mcu/arm/mps2.ld
+
+SRC_BOARD_O = shared/runtime/gchelper_native.o shared/runtime/gchelper_thumb2.o
+
+MPY_CROSS_FLAGS += -march=armv7emdp
+
+MICROPY_FLOAT_IMPL = double
+SUPPORTS_HARDWARE_FP_DOUBLE = 1

ports/qemu/mcu/arm/startup.c

@@ -47,6 +47,12 @@ __attribute__((naked)) void Reset_Handler(void) {
     for (uint32_t *dest = &_sbss; dest < &_ebss;) {
         *dest++ = 0;
     }
+    #if MICROPY_HW_FPU && defined(__ARM_ARCH_ISA_THUMB) && __ARM_ARCH == 7
+    // initialise the FPU (full access to CP10 and CP11, as per B3.2.20)
+    *((volatile uint32_t *)0xE000ED88) |= 0x00F00000;
+    __asm volatile ("dsb");
+    __asm volatile ("isb");
+    #endif
     // jump to board initialisation
     void _start(void);
     _start();