drivers: Implement semihosting based console driver for log

Semihosting is a mechanism that enables target to communicate and use
I/O facilities on a host computer which is running a debugger, such as
GDB. The I/O facilities include character {read|write} {from|to} the
semihosting host side console or a file. In other words, OP-TEE OS can
output log to the host side console or the host side file, if there is a
semihosting host and OP-TEE OS requests the semihosting operations to
that host.

This commit implements a simple console driver which uses semihosting
operations to read/write the character. There are two paths to output
the log:
- If the caller of semihosting_console_init() provides the path of the
  file, the driver will try to open that file, and output the log to
  that host side file.
- If the caller of semihosting_console_init() does not provide the path
  of the file, the driver will try to output the log to host side
  console directly.

Signed-off-by: Alvin Chang <[email protected]>

core/drivers/semihosting_console.c

@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: BSD-2-Clause
+/*
+ * Copyright (c) 2024 Andes Technology Corporation
+ */
+
+#include <compiler.h>
+#include <drivers/semihosting_console.h>
+#include <kernel/semihosting.h>
+#include <util.h>
+
+static void semihosting_console_putc(struct serial_chip *chip __unused, int ch)
+{
+	semihosting_writec(ch);
+}
+
+static int semihosting_console_getchar(struct serial_chip *chip __unused)
+{
+	return semihosting_readc();
+}
+
+static const struct serial_ops semihosting_console_ops = {
+	.putc = semihosting_console_putc,
+	.getchar = semihosting_console_getchar,
+};
+DECLARE_KEEP_PAGER(semihosting_console_ops);
+
+static void semihosting_console_fd_putc(struct serial_chip *chip __unused,
+					int ch)
+{
+	struct semihosting_console_data *pd =
+		container_of(chip, struct semihosting_console_data, chip);
+
+	semihosting_write(pd->fd, &ch, 1);
+}
+
+static const struct serial_ops semihosting_console_fd_ops = {
+	.putc = semihosting_console_fd_putc,
+};
+DECLARE_KEEP_PAGER(semihosting_console_fd_ops);
+
+void semihosting_console_init(struct semihosting_console_data *pd,
+			      const char *file_path)
+{
+	if (file_path) {
+		/* Output log to given file. */
+		pd->chip.ops = &semihosting_console_fd_ops;
+		pd->file_path = file_path;
+		pd->fd = semihosting_open(pd->file_path,
+					  O_RDWR | O_CREAT | O_TRUNC);
+	} else {
+		/* Output log to semihosting console. */
+		pd->chip.ops = &semihosting_console_ops;
+		pd->file_path = NULL;
+		pd->fd = -1;
+	}
+}

core/drivers/sub.mk

@@ -79,6 +79,7 @@ srcs-$(CFG_CBMEM_CONSOLE) += cbmem_console.c
 srcs-$(CFG_RISCV_PLIC) += plic.c
 srcs-$(CFG_HISILICON_CRYPTO_DRIVER) += hisi_trng.c
 srcs-$(CFG_WIDEVINE_HUK) += widevine_huk.c
+srcs-$(CFG_SEMIHOSTING_CONSOLE) += semihosting_console.c
 
 subdirs-y += crypto
 subdirs-$(CFG_BNXT_FW) += bnxt

core/include/drivers/semihosting_console.h

@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (c) 2024 Andes Technology Corporation
+ */
+#ifndef __DRIVERS_SEMIHOSTING_CONSOLE_H
+#define __DRIVERS_SEMIHOSTING_CONSOLE_H
+
+#include <drivers/serial.h>
+
+struct semihosting_console_data {
+	struct serial_chip chip;
+	const char *file_path;
+	int fd;
+};
+
+/*
+ * Initialize console which uses architecture-specific semihosting mechanism.
+ * If "file_path" is not NULL, OP-TEE OS will try to output log to that file.
+ * Otherwise, if "file_path" is NULL, OP-TEE OS will try to output log to the
+ * semihosting console.
+ */
+void semihosting_console_init(struct semihosting_console_data *pd,
+			      const char *file_path);
+
+#endif /* __DRIVERS_SEMIHOSTING_CONSOLE_H */