Implement simple uart-based updater for the bootrom (#2267)

corev_apu/fpga/src/bootrom/src/main.c

@@ -7,12 +7,71 @@
 #include "sd.h"
 #include "gpt.h"
 
+// 1 second at 50MHz
+#define SECOND_CYCLES   (50 * 1000 * 1000)
+#define WAIT_SECONDS    (5)
+
+static inline uintptr_t get_cycle_count() {
+    uintptr_t cycle;
+    __asm__ volatile ("csrr %0, cycle" : "=r" (cycle));
+    return cycle;
+}
+
+int update(uint8_t *dest)
+{
+    int i;
+    uint32_t size = 0;
+
+    print_uart("receiving boot image\r\nsize: ");
+    for(i = 0; i < sizeof(uint32_t); i++) {
+        while(!read_serial(&((uint8_t *) &size)[i]));
+    }
+
+    print_uart_int(size);
+    print_uart("\r\nreceiving ");
+
+    for(i = 0; i < size; i++) {
+        while(!read_serial(&dest[i]));
+
+        if(i % (size >> 4) == 0) {
+            print_uart(".");
+        }
+    }
+
+    print_uart(" done!\r\n");
+    return 0;
+}
+
 int main()
 {
+    int i, ret = 0;
+    uint8_t uart_res = 0;
+    uintptr_t start;
+
     init_uart(CLOCK_FREQUENCY, UART_BITRATE);
     print_uart("Hello World!\r\n");
 
-    int res = gpt_find_boot_partition((uint8_t *)0x80000000UL, 2 * 16384);
+    // See if we should enter update mode
+    print_uart("Hit any key to enter update mode ");
+    for(i = 0; i < WAIT_SECONDS && !ret; i++) {
+        print_uart(".");
+        start = get_cycle_count();
+        while(get_cycle_count() - start < SECOND_CYCLES) {
+            ret = read_serial(&uart_res);
+            if(ret) {
+                break;
+            }
+        }
+    }
+
+    int res;
+    if(ret) {
+        print_uart(" updating!\r\n");
+        res = update((uint8_t *)0x80000000UL);
+    } else {
+        print_uart(" booting!\r\n");
+        res = gpt_find_boot_partition((uint8_t *)0x80000000UL, 2 * 16384);
+    }
 
     if (res == 0)
     {

corev_apu/fpga/src/bootrom/src/uart.c

@@ -20,6 +20,11 @@ int is_transmit_empty()
     return read_reg_u8(UART_LINE_STATUS) & 0x20;
 }
 
+int is_receive_empty()
+{
+    return !(read_reg_u8(UART_LINE_STATUS) & 0x1);
+}
+
 void write_serial(char a)
 {
     while (is_transmit_empty() == 0) {};
@@ -27,6 +32,16 @@ void write_serial(char a)
     write_reg_u8(UART_THR, a);
 }
 
+int read_serial(uint8_t *res)
+{
+    if(is_receive_empty()) {
+        return 0;
+    }
+
+    *res = read_reg_u8(UART_RBR);
+    return 1;
+}
+
 void init_uart(uint32_t freq, uint32_t baud)
 {
     uint32_t divisor = freq / (baud << 4);

corev_apu/fpga/src/bootrom/src/uart.h

@@ -22,6 +22,8 @@
 
 void init_uart();
 
+int read_serial(uint8_t *res);
+
 void print_uart(const char* str);
 
 void print_uart_int(uint32_t addr);