Make it possible to use printf during bare-metal execution.

sw/include/cheshire_io.h

@@ -0,0 +1,13 @@
+// Copyright 2022 ETH Zurich and University of Bologna.
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "regs/cheshire.h"
+#include "dif/clint.h"
+#include "dif/uart.h"
+#include "util.h"
+#include "params.h"
+
+void cheshire_init_io();
+
+void cheshire_close_io();

sw/include/dif/uart.h

@@ -42,6 +42,10 @@ uint8_t uart_read(void *uart_base);
 void uart_read_str(void *uart_base, void *dst, uint64_t len);
 
 // Default UART provides console
-void _putchar(char byte);
+void uart_open();
+
+void _putchar(char character);
 
 char _getchar();
+
+void uart_close();

sw/include/init.h

@@ -0,0 +1,9 @@
+// Copyright 2022 ETH Zurich and University of Bologna.
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "cheshire_io.h"
+
+void soc_init();
+
+void soc_close();

sw/lib/cheshire_io.c

@@ -0,0 +1,29 @@
+// Copyright 2022 ETH Zurich and University of Bologna.
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+//
+// Yvan Tortorella <[email protected]>
+//
+// Library containing IO init/close functions.
+
+#include "cheshire_io.h"
+
+void cheshire_init_io() {
+  // Initialize UART first
+  uart_open();
+
+  // Initialize other IOs
+  // .
+  // .
+  // .
+};
+
+void cheshire_close_io() {
+  // Close UART first
+  uart_close();
+
+  // Close other IOs
+  // .
+  // .
+  // .
+};

sw/lib/crt0.S

@@ -111,8 +111,12 @@ _fp_init:
     // Set FS state to "Clean"
     csrrc x0, mstatus, t1
 
-    // Full fence, then jump to main
+    // Full fence, then init SoC
     fence
+
+    // Init SoC, than jump to main
+    jal x1, soc_init
+
     call main
 
 // If main returns, we end up here
@@ -127,6 +131,8 @@ _exit:
     ori  t0, t0, 1
     la t1, __base_regs
     sw t0, 8(t1)     // regs.SCRATCH[2]
+    // Flush everything before exiting.
+    jal x1, soc_close
     // Hand over to whatever called us, passing return
     ret
 

sw/lib/dif/uart.c

@@ -5,6 +5,8 @@
 // Nils Wistoff <[email protected]>
 // Paul Scheffler <[email protected]>
 
+#include "regs/cheshire.h"
+#include "dif/clint.h"
 #include "dif/uart.h"
 #include "util.h"
 #include "params.h"
@@ -64,10 +66,20 @@ void uart_read_str(void *uart_base, void *dst, uint64_t len) {
 }
 
 // Default UART provides console
-void _putchar(char byte) {
-    uart_write(&__base_uart, byte);
+void uart_open(){
+  uint32_t rtc_freq = *reg32(&__base_regs, CHESHIRE_RTC_FREQ_REG_OFFSET);
+  uint64_t reset_freq = clint_get_core_freq(rtc_freq, 2500);
+  uart_init(&__base_uart, reset_freq, 115200);
+};
+
+void _putchar(char character) {
+    uart_write(&__base_uart, character);
 };
 
 char _getchar() {
     return uart_read(&__base_uart);
 };
+
+void uart_close() {
+  uart_write_flush(&__base_uart);
+};

sw/lib/init.c

@@ -0,0 +1,18 @@
+// Copyright 2022 ETH Zurich and University of Bologna.
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+//
+// Yvan Tortorella <[email protected]>
+//
+// Library containing general SoC init/close functions.
+
+#include "init.h"
+
+void soc_init() {
+  // IO initialization
+  cheshire_init_io();
+};
+
+void soc_close() {
+  cheshire_close_io();
+};