Add basic flash impl

ld/STM32F031x6.ld

@@ -1,6 +1,7 @@
 MEMORY
 {
-    FLASH (rx)  : ORIGIN = 0x8000000, LENGTH = 32K
+    /* Last 1k is for settings */
+    FLASH (rx)  : ORIGIN = 0x8000000, LENGTH = 32K - 1K
     RAM (rwx)   : ORIGIN = 0x20000000, LENGTH = 4K
 }
 INCLUDE ld/gcc_arm.ld

src/tinyhw.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "hwconfig.h"
+
 #define RAM_FUNC __attribute__((noinline, long_call, section(".data")))
 
 // exti.c
@@ -58,3 +60,8 @@ int target_in_irq(void);
 // init.c
 bool clk_is_pll(void);
 void clk_set_pll(int on);
+
+
+// flash.c
+void flash_program(void *dst, const void *src, uint32_t len);
+void flash_erase(void *page_addr);

stm32/flash.c

@@ -0,0 +1,52 @@
+#include "jdstm.h"
+
+#define WAIT_BUSY()                                                                                \
+    while (FLASH->SR & FLASH_SR_BSY)                                                               \
+        ;
+
+static void unlock() {
+    WAIT_BUSY();
+    if (FLASH->CR & FLASH_CR_LOCK) {
+        FLASH->KEYR = 0x45670123;
+        FLASH->KEYR = 0xCDEF89AB;
+    }
+}
+
+static void lock() {
+    FLASH->CR &= ~(FLASH_CR_PG | FLASH_CR_PER);
+    FLASH->CR |= FLASH_CR_LOCK;
+}
+
+static void check_eop() {
+    WAIT_BUSY();
+    if (FLASH->SR & FLASH_SR_EOP)
+        FLASH->SR = FLASH_SR_EOP;
+    else
+        jd_panic();
+}
+
+void flash_program(void *dst, const void *src, uint32_t len) {
+    if ((((uint32_t)dst) & 1) || (((uint32_t)src) & 1) || (len & 1))
+        jd_panic();
+
+    unlock();
+    FLASH->CR |= FLASH_CR_PG; // enable programming
+
+    while (len--) {
+        *(__IO uint16_t *)(dst) = *(uint16_t *)src;
+        check_eop();
+        dst = (uint16_t *)dst + 1;
+        src = (uint16_t *)src + 1;
+    }
+
+    lock();
+}
+
+void flash_erase(void *page_addr) {
+    unlock();
+    FLASH->CR |= FLASH_CR_PER;
+    FLASH->AR = (uint32_t)page_addr;
+    FLASH->CR |= FLASH_CR_STRT;
+    check_eop();
+    lock();
+}

stm32/hwconfig.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#if defined(STM32F030x4)
+#define STM32F030x6 1 // HAL requires that
+#define FLASH_PAGE_SIZE 1024
+#define FLASH_PAGES 16
+#elif defined(STM32F031x6)
+#define FLASH_PAGE_SIZE 1024
+#define FLASH_PAGES 32
+#else
+#error "define flash size"
+#endif
+
+#define FLASH_SIZE (FLASH_PAGE_SIZE * FLASH_PAGES)
+#define SETTINGS_START (FLASH_SIZE - FLASH_PAGE_SIZE)
+#define SETTINGS_SIZE FLASH_PAGE_SIZE