efi: Add a serial driver

Add a serial driver which makes use of EFI's console in/out service.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested on Intel Crown Bay and QEMU
Tested-by: Bin Meng <bmeng.cn@gmail.com>

drivers/serial/Kconfig

@@ -44,6 +44,15 @@ config DEBUG_UART_NS16550
 	  will need to provide parameters to make this work. The driver will
 	  be available until the real driver model serial is running.
 
+config DEBUG_EFI_CONSOLE
+	bool "EFI"
+	depends on EFI_APP
+	help
+	  Select this to enable a debug console which calls back to EFI to
+	  output to the console. This can be useful for early debugging of
+	  U-Boot when running on top of EFI (Extensive Firmware Interface).
+	  This is a type of BIOS used by PCs.
+
 endchoice
 
 config DEBUG_UART_BASE

drivers/serial/Makefile

@@ -21,6 +21,7 @@ obj-$(CONFIG_ALTERA_JTAG_UART) += altera_jtag_uart.o
 obj-$(CONFIG_ARM_DCC) += arm_dcc.o
 obj-$(CONFIG_ATMEL_USART) += atmel_usart.o
 obj-$(CONFIG_DW_SERIAL) += serial_dw.o
+obj-$(CONFIG_EFI_APP) += serial_efi.o
 obj-$(CONFIG_LPC32XX_HSUART) += lpc32xx_hsuart.o
 obj-$(CONFIG_MCFUART) += mcfuart.o
 obj-$(CONFIG_OPENCORES_YANU) += opencores_yanu.o

drivers/serial/serial_efi.c

+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <debug_uart.h>
+#include <dm.h>
+#include <efi.h>
+#include <efi_api.h>
+#include <errno.h>
+#include <fdtdec.h>
+#include <linux/compiler.h>
+#include <asm/io.h>
+#include <serial.h>
+
+/* Information about the efi console */
+struct serial_efi_priv {
+	struct efi_simple_input_interface *con_in;
+	struct efi_simple_text_output_protocol *con_out;
+	struct efi_input_key key;
+	bool have_key;
+};
+
+int serial_efi_setbrg(struct udevice *dev, int baudrate)
+{
+	return 0;
+}
+
+static int serial_efi_get_key(struct serial_efi_priv *priv)
+{
+	int ret;
+
+	if (priv->have_key)
+		return 0;
+	ret = priv->con_in->read_key_stroke(priv->con_in, &priv->key);
+	if (ret == EFI_NOT_READY)
+		return -EAGAIN;
+	else if (ret != EFI_SUCCESS)
+		return -EIO;
+
+	priv->have_key = true;
+
+	return 0;
+}
+
+static int serial_efi_getc(struct udevice *dev)
+{
+	struct serial_efi_priv *priv = dev_get_priv(dev);
+	int ret, ch;
+
+	ret = serial_efi_get_key(priv);
+	if (ret)
+		return ret;
+
+	priv->have_key = false;
+	ch = priv->key.unicode_char;
+
+	/*
+	 * Unicode char 8 (for backspace) is never returned. Instead we get a
+	 * key scan code of 8. Handle this so that backspace works correctly
+	 * in the U-Boot command line.
+	 */
+	if (!ch && priv->key.scan_code == 8)
+		ch = 8;
+	debug(" [%x %x %x] ", ch, priv->key.unicode_char, priv->key.scan_code);
+
+	return ch;
+}
+
+static int serial_efi_putc(struct udevice *dev, const char ch)
+{
+	struct serial_efi_priv *priv = dev_get_priv(dev);
+	uint16_t ucode[2];
+	int ret;
+
+	ucode[0] = ch;
+	ucode[1] = '\0';
+	ret = priv->con_out->output_string(priv->con_out, ucode);
+	if (ret)
+		return -EIO;
+
+	return 0;
+}
+
+static int serial_efi_pending(struct udevice *dev, bool input)
+{
+	struct serial_efi_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	/* We assume that EFI will stall if its output buffer fills up */
+	if (!input)
+		return 0;
+
+	ret = serial_efi_get_key(priv);
+	if (ret == -EAGAIN)
+		return 0;
+	else if (ret)
+		return ret;
+
+	return 1;
+}
+
+/*
+ * There is nothing to init here since the EFI console is already running by
+ * the time we enter U-Boot.
+ */
+void debug_uart_init(void)
+{
+}
+
+static inline void _debug_uart_putc(int ch)
+{
+	struct efi_system_table *sys_table = efi_get_sys_table();
+	uint16_t ucode[2];
+
+	ucode[0] = ch;
+	ucode[1] = '\0';
+	sys_table->con_out->output_string(sys_table->con_out, ucode);
+}
+
+DEBUG_UART_FUNCS
+
+static int serial_efi_probe(struct udevice *dev)
+{
+	struct efi_system_table *table = efi_get_sys_table();
+	struct serial_efi_priv *priv = dev_get_priv(dev);
+
+	priv->con_in = table->con_in;
+	priv->con_out = table->con_out;
+
+	return 0;
+}
+
+static const struct dm_serial_ops serial_efi_ops = {
+	.putc = serial_efi_putc,
+	.getc = serial_efi_getc,
+	.pending = serial_efi_pending,
+	.setbrg = serial_efi_setbrg,
+};
+
+static const struct udevice_id serial_efi_ids[] = {
+	{ .compatible = "efi,uart" },
+	{ }
+};
+
+U_BOOT_DRIVER(serial_efi) = {
+	.name	= "serial_efi",
+	.id	= UCLASS_SERIAL,
+	.of_match = serial_efi_ids,
+	.priv_auto_alloc_size = sizeof(struct serial_efi_priv),
+	.probe = serial_efi_probe,
+	.ops	= &serial_efi_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};