stm32: Add support for Cortex-M0 CPUs.

ports/stm32/gchelper_m0.s

@@ -0,0 +1,61 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+    .syntax unified
+    .cpu cortex-m0
+    .thumb
+
+    .section .text
+    .align 2
+
+    .global gc_helper_get_regs_and_sp
+    .type gc_helper_get_regs_and_sp, %function
+
+@ uint gc_helper_get_regs_and_sp(r0=uint regs[10])
+gc_helper_get_regs_and_sp:
+    @ store registers into given array
+    str    r4, [r0, #0]
+    str    r5, [r0, #4]
+    str    r6, [r0, #8]
+    str    r7, [r0, #12]
+    mov    r1, r8
+    str    r1, [r0, #16]
+    mov    r1, r9
+    str    r1, [r0, #20]
+    mov    r1, r10
+    str    r1, [r0, #24]
+    mov    r1, r11
+    str    r1, [r0, #28]
+    mov    r1, r12
+    str    r1, [r0, #32]
+    mov    r1, r13
+    str    r1, [r0, #36]
+
+    @ return the sp
+    mov    r0, sp
+    bx     lr
+
+    .size gc_helper_get_regs_and_sp, .-gc_helper_get_regs_and_sp

ports/stm32/irq.h

@@ -102,6 +102,24 @@ MP_DECLARE_CONST_FUN_OBJ_0(pyb_irq_stats_obj);
 // The following interrupts are arranged from highest priority to lowest
 // priority to make it a bit easier to figure out.
 
+#if __CORTEX_M == 0
+
+//#def  IRQ_PRI_SYSTICK         0
+#define IRQ_PRI_UART            1
+#define IRQ_PRI_FLASH           1
+#define IRQ_PRI_SDIO            1
+#define IRQ_PRI_DMA             1
+#define IRQ_PRI_OTG_FS          2
+#define IRQ_PRI_OTG_HS          2
+#define IRQ_PRI_TIM5            2
+#define IRQ_PRI_CAN             2
+#define IRQ_PRI_TIMX            2
+#define IRQ_PRI_EXTINT          2
+#define IRQ_PRI_PENDSV          3
+#define IRQ_PRI_RTC_WKUP        3
+
+#else
+
 //#def  IRQ_PRI_SYSTICK         NVIC_EncodePriority(NVIC_PRIORITYGROUP_4, 0, 0)
 
 // The UARTs have no FIFOs, so if they don't get serviced quickly then characters
@@ -135,4 +153,6 @@ MP_DECLARE_CONST_FUN_OBJ_0(pyb_irq_stats_obj);
 #define IRQ_PRI_PENDSV          NVIC_EncodePriority(NVIC_PRIORITYGROUP_4, 15, 0)
 #define IRQ_PRI_RTC_WKUP        NVIC_EncodePriority(NVIC_PRIORITYGROUP_4, 15, 0)
 
+#endif
+
 #endif // MICROPY_INCLUDED_STM32_IRQ_H

ports/stm32/main.c

@@ -458,8 +458,10 @@ void stm32_main(uint32_t reset_mode) {
 
     #endif
 
+    #if __CORTEX_M >= 0x03
     // Set the priority grouping
     NVIC_SetPriorityGrouping(NVIC_PRIORITYGROUP_4);
+    #endif
 
     // SysTick is needed by HAL_RCC_ClockConfig (called in SystemClock_Config)
     HAL_InitTick(TICK_INT_PRIORITY);

ports/stm32/mphalport.c

@@ -87,6 +87,7 @@ void mp_hal_stdout_tx_strn_cooked(const char *str, size_t len) {
     }
 }
 
+#if __CORTEX_M >= 0x03
 void mp_hal_ticks_cpu_enable(void) {
     if (!(DWT->CTRL & DWT_CTRL_CYCCNTENA_Msk)) {
         CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
@@ -98,6 +99,7 @@ void mp_hal_ticks_cpu_enable(void) {
         DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
     }
 }
+#endif
 
 void mp_hal_gpio_clock_enable(GPIO_TypeDef *gpio) {
     #if defined(STM32L476xx) || defined(STM32L496xx)

ports/stm32/mphalport.h

@@ -11,16 +11,26 @@ void mp_hal_set_interrupt_char(int c); // -1 to disable
 
 #include "irq.h"
 
+#if __CORTEX_M == 0
+// Don't have raise_irq_pri on Cortex-M0 so keep IRQs enabled to have SysTick timing
+#define mp_hal_quiet_timing_enter() (1)
+#define mp_hal_quiet_timing_exit(irq_state) (void)(irq_state)
+#else
 #define mp_hal_quiet_timing_enter() raise_irq_pri(1)
 #define mp_hal_quiet_timing_exit(irq_state) restore_irq_pri(irq_state)
+#endif
 #define mp_hal_delay_us_fast(us) mp_hal_delay_us(us)
 
 void mp_hal_ticks_cpu_enable(void);
 static inline mp_uint_t mp_hal_ticks_cpu(void) {
+    #if __CORTEX_M == 0
+    return 0;
+    #else
     if (!(DWT->CTRL & DWT_CTRL_CYCCNTENA_Msk)) {
         mp_hal_ticks_cpu_enable();
     }
     return DWT->CYCCNT;
+    #endif
 }
 
 // C-level pin HAL

ports/stm32/resethandler_m0.s

@@ -0,0 +1,74 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+    .syntax unified
+    .cpu cortex-m0
+    .thumb
+
+    .section .text.Reset_Handler
+    .global Reset_Handler
+    .type Reset_Handler, %function
+
+Reset_Handler:
+    /* Save the first argument to pass through to stm32_main */
+    mov  r4, r0
+
+    /* Load the stack pointer */
+    ldr  r0, =_estack
+    mov  sp, r0
+
+    /* Initialise the data section */
+    ldr  r1, =_sidata
+    ldr  r2, =_sdata
+    ldr  r3, =_edata
+    b    .data_copy_entry
+.data_copy_loop:
+    ldr  r0, [r1]
+    adds r1, #4
+    str  r0, [r2]
+    adds r2, #4
+.data_copy_entry:
+    cmp  r2, r3
+    bcc  .data_copy_loop
+
+    /* Zero out the BSS section */
+    movs r0, #0
+    ldr  r1, =_sbss
+    ldr  r2, =_ebss
+    b    .bss_zero_entry
+.bss_zero_loop:
+    str  r0, [r1]
+    adds r1, #4
+.bss_zero_entry:
+    cmp  r1, r2
+    bcc  .bss_zero_loop
+
+    /* Initialise the system and jump to the main code */
+    bl   SystemInit
+    mov  r0, r4
+    bl   stm32_main
+
+    .size Reset_Handler, .-Reset_Handler

ports/stm32/stm32_it.c

@@ -165,6 +165,7 @@ void HardFault_C_Handler(ExceptionRegisters_t *regs) {
     print_reg("PC    ", regs->pc);
     print_reg("XPSR  ", regs->xpsr);
 
+    #if __CORTEX_M >= 3
     uint32_t cfsr = SCB->CFSR;
 
     print_reg("HFSR  ", SCB->HFSR);
@@ -175,6 +176,7 @@ void HardFault_C_Handler(ExceptionRegisters_t *regs) {
     if (cfsr & 0x8000) {
         print_reg("BFAR  ", SCB->BFAR);
     }
+    #endif
 
     if ((void*)&_ram_start <= (void*)regs && (void*)regs < (void*)&_ram_end) {
         mp_hal_stdout_tx_str("Stack:\r\n");
@@ -207,6 +209,17 @@ void HardFault_Handler(void) {
     // main stack pointer (aka MSP). If CONTROL.SPSEL is 1, then the exception
     // was stacked up using the process stack pointer (aka PSP).
 
+    #if __CORTEX_M == 0
+    __asm volatile(
+    " mov r0, lr    \n"
+    " lsr r0, r0, #3 \n"        // Shift Bit 3 into carry to see which stack pointer we should use.
+    " mrs r0, msp   \n"         // Make R0 point to main stack pointer
+    " bcc .use_msp  \n"         // Keep MSP in R0 if SPSEL (carry) is 0
+    " mrs r0, psp   \n"         // Make R0 point to process stack pointer
+    " .use_msp:     \n"
+    " b HardFault_C_Handler \n" // Off to C land
+    );
+    #else
     __asm volatile(
     " tst lr, #4    \n"         // Test Bit 3 to see which stack pointer we should use.
     " ite eq        \n"         // Tell the assembler that the nest 2 instructions are if-then-else
@@ -214,6 +227,7 @@ void HardFault_Handler(void) {
     " mrsne r0, psp \n"         // Make R0 point to process stack pointer
     " b HardFault_C_Handler \n" // Off to C land
     );
+    #endif
 }
 
 /**