drivers/serial/serial.c - filogic/uboot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * (C) Copyright 2004
  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
  */

 #include <common.h>
 #include <env_internal.h>
 #include <hang.h>
 #include <serial.h>
 #include <stdio_dev.h>
 #include <post.h>
 #include <asm/global_data.h>
 #include <linux/compiler.h>
 #include <errno.h>
 #include <linux/delay.h>

 DECLARE_GLOBAL_DATA_PTR;

 static struct serial_device *serial_devices;
 static struct serial_device *serial_current;
 /*
  * Table with supported baudrates (defined in config_xyz.h)
  */
 static const unsigned long baudrate_table[] = CFG_SYS_BAUDRATE_TABLE;

 /**
  * serial_null() - Void registration routine of a serial driver
  *
  * This routine implements a void registration routine of a serial
  * driver. The registration routine of a particular driver is aliased
  * to this empty function in case the driver is not compiled into
  * U-Boot.
  */
 static void serial_null(void)
 {
 }

 /**
  * on_baudrate() - Update the actual baudrate when the env var changes
  *
  * @name:	changed environment variable
  * @value:	new value of the environment variable
  * @op:		operation (create, overwrite, or delete)
  * @flags:	attributes of environment variable change,
  *		see flags H_* in include/search.h
  *
  * This will check for a valid baudrate and only apply it if valid.
  *
  * Return:	0 on success, 1 on error
  */
 static int on_baudrate(const char *name, const char *value, enum env_op op,
 	int flags)
 {
 	int i;
 	int baudrate;

 	switch (op) {
 	case env_op_create:
 	case env_op_overwrite:
 		/*
 		 * Switch to new baudrate if new baudrate is supported
 		 */
 		baudrate = dectoul(value, NULL);

 		/* Not actually changing */
 		if (gd->baudrate == baudrate)
 			return 0;

 		for (i = 0; i < ARRAY_SIZE(baudrate_table); ++i) {
 			if (baudrate == baudrate_table[i])
 				break;
 		}
 		if (i == ARRAY_SIZE(baudrate_table)) {
 			if ((flags & H_FORCE) == 0)
 				printf("## Baudrate %d bps not supported\n",
 					baudrate);
 			return 1;
 		}
 		if ((flags & H_INTERACTIVE) != 0) {
 			printf("## Switch baudrate to %d"
 				" bps and press ENTER ...\n", baudrate);
 			udelay(50000);
 		}

 		gd->baudrate = baudrate;

 		serial_setbrg();

 		udelay(50000);

 		if ((flags & H_INTERACTIVE) != 0)
 			while (1) {
 				if (getchar() == '\r')
 					break;
 			}

 		return 0;
 	case env_op_delete:
 		printf("## Baudrate may not be deleted\n");
 		return 1;
 	default:
 		return 0;
 	}
 }
 U_BOOT_ENV_CALLBACK(baudrate, on_baudrate);

 /**
  * serial_initfunc() - Forward declare of driver registration routine
  * @name:	Name of the real driver registration routine.
  *
  * This macro expands onto forward declaration of a driver registration
  * routine, which is then used below in serial_initialize() function.
  * The declaration is made weak and aliases to serial_null() so in case
  * the driver is not compiled in, the function is still declared and can
  * be used, but aliases to serial_null() and thus is optimized away.
  */
 #define serial_initfunc(name)					\
 	void name(void)						\
 		__attribute__((weak, alias("serial_null")));

 serial_initfunc(atmel_serial_initialize);
 serial_initfunc(mcf_serial_initialize);
 serial_initfunc(mpc85xx_serial_initialize);
 serial_initfunc(mxc_serial_initialize);
 serial_initfunc(ns16550_serial_initialize);
 serial_initfunc(pl01x_serial_initialize);
 serial_initfunc(pxa_serial_initialize);
 serial_initfunc(smh_serial_initialize);
 serial_initfunc(sh_serial_initialize);
 serial_initfunc(mtk_serial_initialize);

 /**
  * serial_register() - Register serial driver with serial driver core
  * @dev:	Pointer to the serial driver structure
  *
  * This function registers the serial driver supplied via @dev with
  * serial driver core, thus making U-Boot aware of it and making it
  * available for U-Boot to use. On platforms that still require manual
  * relocation of constant variables, relocation of the supplied structure
  * is performed.
  */
 void serial_register(struct serial_device *dev)
 {
 #ifdef CONFIG_NEEDS_MANUAL_RELOC
 	if (dev->start)
 		dev->start += gd->reloc_off;
 	if (dev->stop)
 		dev->stop += gd->reloc_off;
 	if (dev->setbrg)
 		dev->setbrg += gd->reloc_off;
 	if (dev->getc)
 		dev->getc += gd->reloc_off;
 	if (dev->tstc)
 		dev->tstc += gd->reloc_off;
 	if (dev->putc)
 		dev->putc += gd->reloc_off;
 	if (dev->puts)
 		dev->puts += gd->reloc_off;
 #endif

 	dev->next = serial_devices;
 	serial_devices = dev;
 }

 /**
  * serial_initialize() - Register all compiled-in serial port drivers
  *
  * This function registers all serial port drivers that are compiled
  * into the U-Boot binary with the serial core, thus making them
  * available to U-Boot to use. Lastly, this function assigns a default
  * serial port to the serial core. That serial port is then used as a
  * default output.
  */
 int serial_initialize(void)
 {
 	atmel_serial_initialize();
 	mcf_serial_initialize();
 	mpc85xx_serial_initialize();
 	mxc_serial_initialize();
 	ns16550_serial_initialize();
 	pl01x_serial_initialize();
 	pxa_serial_initialize();
 	smh_serial_initialize();
 	sh_serial_initialize();
 	mtk_serial_initialize();

 	serial_assign(default_serial_console()->name);

 	return 0;
 }

 static int serial_stub_start(struct stdio_dev *sdev)
 {
 	struct serial_device *dev = sdev->priv;

 	return dev->start();
 }

 static int serial_stub_stop(struct stdio_dev *sdev)
 {
 	struct serial_device *dev = sdev->priv;

 	return dev->stop();
 }

 static void serial_stub_putc(struct stdio_dev *sdev, const char ch)
 {
 	struct serial_device *dev = sdev->priv;

 	dev->putc(ch);
 }

 static void serial_stub_puts(struct stdio_dev *sdev, const char *str)
 {
 	struct serial_device *dev = sdev->priv;

 	dev->puts(str);
 }

 static int serial_stub_getc(struct stdio_dev *sdev)
 {
 	struct serial_device *dev = sdev->priv;

 	return dev->getc();
 }

 static int serial_stub_tstc(struct stdio_dev *sdev)
 {
 	struct serial_device *dev = sdev->priv;

 	return dev->tstc();
 }

 /**
  * serial_stdio_init() - Register serial ports with STDIO core
  *
  * This function generates a proxy driver for each serial port driver.
  * These proxy drivers then register with the STDIO core, making the
  * serial drivers available as STDIO devices.
  */
 void serial_stdio_init(void)
 {
 	struct stdio_dev dev;
 	struct serial_device *s = serial_devices;

 	while (s) {
 		memset(&dev, 0, sizeof(dev));

 		strcpy(dev.name, s->name);
 		dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT;

 		dev.start = serial_stub_start;
 		dev.stop = serial_stub_stop;
 		dev.putc = serial_stub_putc;
 		dev.puts = serial_stub_puts;
 		dev.getc = serial_stub_getc;
 		dev.tstc = serial_stub_tstc;
 		dev.priv = s;

 		stdio_register(&dev);

 		s = s->next;
 	}
 }

 /**
  * serial_assign() - Select the serial output device by name
  * @name:	Name of the serial driver to be used as default output
  *
  * This function configures the serial output multiplexing by
  * selecting which serial device will be used as default. In case
  * the STDIO "serial" device is selected as stdin/stdout/stderr,
  * the serial device previously configured by this function will be
  * used for the particular operation.
  *
  * Returns 0 on success, negative on error.
  */
 int serial_assign(const char *name)
 {
 	struct serial_device *s;

 	for (s = serial_devices; s; s = s->next) {
 		if (strcmp(s->name, name))
 			continue;
 		serial_current = s;
 		return 0;
 	}

 	return -EINVAL;
 }

 /**
  * serial_reinit_all() - Reinitialize all compiled-in serial ports
  *
  * This function reinitializes all serial ports that are compiled
  * into U-Boot by calling their serial_start() functions.
  */
 void serial_reinit_all(void)
 {
 	struct serial_device *s;

 	for (s = serial_devices; s; s = s->next)
 		s->start();
 }

 /**
  * get_current() - Return pointer to currently selected serial port
  *
  * This function returns a pointer to currently selected serial port.
  * The currently selected serial port is altered by serial_assign()
  * function.
  *
  * In case this function is called before relocation or before any serial
  * port is configured, this function calls default_serial_console() to
  * determine the serial port. Otherwise, the configured serial port is
  * returned.
  *
  * Returns pointer to the currently selected serial port on success,
  * NULL on error.
  */
 static struct serial_device *get_current(void)
 {
 	struct serial_device *dev;

 	if (!(gd->flags & GD_FLG_RELOC))
 		dev = default_serial_console();
 	else if (!serial_current)
 		dev = default_serial_console();
 	else
 		dev = serial_current;

 	/* We must have a console device */
 	if (!dev) {
 #ifdef CONFIG_SPL_BUILD
 		puts("Cannot find console\n");
 		hang();
 #else
 		panic("Cannot find console\n");
 #endif
 	}

 	return dev;
 }

 /**
  * serial_init() - Initialize currently selected serial port
  *
  * This function initializes the currently selected serial port. This
  * usually involves setting up the registers of that particular port,
  * enabling clock and such. This function uses the get_current() call
  * to determine which port is selected.
  *
  * Returns 0 on success, negative on error.
  */
 int serial_init(void)
 {
 	gd->flags |= GD_FLG_SERIAL_READY;
 	return get_current()->start();
 }

 /**
  * serial_setbrg() - Configure baud-rate of currently selected serial port
  *
  * This function configures the baud-rate of the currently selected
  * serial port. The baud-rate is retrieved from global data within
  * the serial port driver. This function uses the get_current() call
  * to determine which port is selected.
  *
  * Returns 0 on success, negative on error.
  */
 void serial_setbrg(void)
 {
 	get_current()->setbrg();
 }

 /**
  * serial_getc() - Read character from currently selected serial port
  *
  * This function retrieves a character from currently selected serial
  * port. In case there is no character waiting on the serial port,
  * this function will block and wait for the character to appear. This
  * function uses the get_current() call to determine which port is
  * selected.
  *
  * Returns the character on success, negative on error.
  */
 int serial_getc(void)
 {
 	return get_current()->getc();
 }

 /**
  * serial_tstc() - Test if data is available on currently selected serial port
  *
  * This function tests if one or more characters are available on
  * currently selected serial port. This function never blocks. This
  * function uses the get_current() call to determine which port is
  * selected.
  *
  * Returns positive if character is available, zero otherwise.
  */
 int serial_tstc(void)
 {
 	return get_current()->tstc();
 }

 /**
  * serial_putc() - Output character via currently selected serial port
  * @c:	Single character to be output from the serial port.
  *
  * This function outputs a character via currently selected serial
  * port. This character is passed to the serial port driver responsible
  * for controlling the hardware. The hardware may still be in process
  * of transmitting another character, therefore this function may block
  * for a short amount of time. This function uses the get_current()
  * call to determine which port is selected.
  */
 void serial_putc(const char c)
 {
 	get_current()->putc(c);
 }

 /**
  * serial_puts() - Output string via currently selected serial port
  * @s:	Zero-terminated string to be output from the serial port.
  *
  * This function outputs a zero-terminated string via currently
  * selected serial port. This function behaves as an accelerator
  * in case the hardware can queue multiple characters for transfer.
  * The whole string that is to be output is available to the function
  * implementing the hardware manipulation. Transmitting the whole
  * string may take some time, thus this function may block for some
  * amount of time. This function uses the get_current() call to
  * determine which port is selected.
  */
 void serial_puts(const char *s)
 {
 	get_current()->puts(s);
 }

 /**
  * default_serial_puts() - Output string by calling serial_putc() in loop
  * @s:	Zero-terminated string to be output from the serial port.
  *
  * This function outputs a zero-terminated string by calling serial_putc()
  * in a loop. Most drivers do not support queueing more than one byte for
  * transfer, thus this function precisely implements their serial_puts().
  *
  * To optimize the number of get_current() calls, this function only
  * calls get_current() once and then directly accesses the putc() call
  * of the &struct serial_device .
  */
 void default_serial_puts(const char *s)
 {
 	struct serial_device *dev = get_current();
 	while (*s)
 		dev->putc(*s++);
 }

 #if CFG_POST & CONFIG_SYS_POST_UART
 static const int bauds[] = CFG_SYS_BAUDRATE_TABLE;

 /**
  * uart_post_test() - Test the currently selected serial port using POST
  * @flags:	POST framework flags
  *
  * Do a loopback test of the currently selected serial port. This
  * function is only useful in the context of the POST testing framwork.
  * The serial port is first configured into loopback mode and then
  * characters are sent through it.
  *
  * Returns 0 on success, value otherwise.
  */
 /* Mark weak until post/cpu/.../uart.c migrate over */
 __weak
 int uart_post_test(int flags)
 {
 	unsigned char c;
 	int ret, saved_baud, b;
 	struct serial_device *saved_dev, *s;

 	/* Save current serial state */
 	ret = 0;
 	saved_dev = serial_current;
 	saved_baud = gd->baudrate;

 	for (s = serial_devices; s; s = s->next) {
 		/* If this driver doesn't support loop back, skip it */
 		if (!s->loop)
 			continue;

 		/* Test the next device */
 		serial_current = s;

 		ret = serial_init();
 		if (ret)
 			goto done;

 		/* Consume anything that happens to be queued */
 		while (serial_tstc())
 			serial_getc();

 		/* Enable loop back */
 		s->loop(1);

 		/* Test every available baud rate */
 		for (b = 0; b < ARRAY_SIZE(bauds); ++b) {
 			gd->baudrate = bauds[b];
 			serial_setbrg();

 			/*
 			 * Stick to printable chars to avoid issues:
 			 *  - terminal corruption
 			 *  - serial program reacting to sequences and sending
 			 *    back random extra data
 			 *  - most serial drivers add in extra chars (like \r\n)
 			 */
 			for (c = 0x20; c < 0x7f; ++c) {
 				/* Send it out */
 				serial_putc(c);

 				/* Make sure it's the same one */
 				ret = (c != serial_getc());
 				if (ret) {
 					s->loop(0);
 					goto done;
 				}

 				/* Clean up the output in case it was sent */
 				serial_putc('\b');
 				ret = ('\b' != serial_getc());
 				if (ret) {
 					s->loop(0);
 					goto done;
 				}
 			}
 		}

 		/* Disable loop back */
 		s->loop(0);

 		/* XXX: There is no serial_stop() !? */
 		if (s->stop)
 			s->stop();
 	}

  done:
 	/* Restore previous serial state */
 	serial_current = saved_dev;
 	gd->baudrate = saved_baud;
 	serial_reinit_all();
 	serial_setbrg();

 	return ret;
 }
 #endif
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* (C) Copyright 2004
	* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
	*/

	#include <common.h>
	#include <env_internal.h>
	#include <hang.h>
	#include <serial.h>
	#include <stdio_dev.h>
	#include <post.h>
	#include <asm/global_data.h>
	#include <linux/compiler.h>
	#include <errno.h>
	#include <linux/delay.h>

	DECLARE_GLOBAL_DATA_PTR;

	static struct serial_device *serial_devices;
	static struct serial_device *serial_current;
	/*
	* Table with supported baudrates (defined in config_xyz.h)
	*/
	static const unsigned long baudrate_table[] = CFG_SYS_BAUDRATE_TABLE;

	/**
	* serial_null() - Void registration routine of a serial driver
	*
	* This routine implements a void registration routine of a serial
	* driver. The registration routine of a particular driver is aliased
	* to this empty function in case the driver is not compiled into
	* U-Boot.
	*/
	static void serial_null(void)
	{
	}

	/**
	* on_baudrate() - Update the actual baudrate when the env var changes
	*
	* @name: changed environment variable
	* @value: new value of the environment variable
	* @op: operation (create, overwrite, or delete)
	* @flags: attributes of environment variable change,
	* see flags H_* in include/search.h
	*
	* This will check for a valid baudrate and only apply it if valid.
	*
	* Return: 0 on success, 1 on error
	*/
	static int on_baudrate(const char name, const char value, enum env_op op,
	int flags)
	{
	int i;
	int baudrate;

	switch (op) {
	case env_op_create:
	case env_op_overwrite:
	/*
	* Switch to new baudrate if new baudrate is supported
	*/
	baudrate = dectoul(value, NULL);

	/* Not actually changing */
	if (gd->baudrate == baudrate)
	return 0;

	for (i = 0; i < ARRAY_SIZE(baudrate_table); ++i) {
	if (baudrate == baudrate_table[i])
	break;
	}
	if (i == ARRAY_SIZE(baudrate_table)) {
	if ((flags & H_FORCE) == 0)
	printf("## Baudrate %d bps not supported\n",
	baudrate);
	return 1;
	}
	if ((flags & H_INTERACTIVE) != 0) {
	printf("## Switch baudrate to %d"
	" bps and press ENTER ...\n", baudrate);
	udelay(50000);
	}

	gd->baudrate = baudrate;

	serial_setbrg();

	udelay(50000);

	if ((flags & H_INTERACTIVE) != 0)
	while (1) {
	if (getchar() == '\r')
	break;
	}

	return 0;
	case env_op_delete:
	printf("## Baudrate may not be deleted\n");
	return 1;
	default:
	return 0;
	}
	}
	U_BOOT_ENV_CALLBACK(baudrate, on_baudrate);

	/**
	* serial_initfunc() - Forward declare of driver registration routine
	* @name: Name of the real driver registration routine.
	*
	* This macro expands onto forward declaration of a driver registration
	* routine, which is then used below in serial_initialize() function.
	* The declaration is made weak and aliases to serial_null() so in case
	* the driver is not compiled in, the function is still declared and can
	* be used, but aliases to serial_null() and thus is optimized away.
	*/
	#define serial_initfunc(name) \
	void name(void) \
	__attribute__((weak, alias("serial_null")));

	serial_initfunc(atmel_serial_initialize);
	serial_initfunc(mcf_serial_initialize);
	serial_initfunc(mpc85xx_serial_initialize);
	serial_initfunc(mxc_serial_initialize);
	serial_initfunc(ns16550_serial_initialize);
	serial_initfunc(pl01x_serial_initialize);
	serial_initfunc(pxa_serial_initialize);
	serial_initfunc(smh_serial_initialize);
	serial_initfunc(sh_serial_initialize);
	serial_initfunc(mtk_serial_initialize);

	/**
	* serial_register() - Register serial driver with serial driver core
	* @dev: Pointer to the serial driver structure
	*
	* This function registers the serial driver supplied via @dev with
	* serial driver core, thus making U-Boot aware of it and making it
	* available for U-Boot to use. On platforms that still require manual
	* relocation of constant variables, relocation of the supplied structure
	* is performed.
	*/
	void serial_register(struct serial_device *dev)
	{
	#ifdef CONFIG_NEEDS_MANUAL_RELOC
	if (dev->start)
	dev->start += gd->reloc_off;
	if (dev->stop)
	dev->stop += gd->reloc_off;
	if (dev->setbrg)
	dev->setbrg += gd->reloc_off;
	if (dev->getc)
	dev->getc += gd->reloc_off;
	if (dev->tstc)
	dev->tstc += gd->reloc_off;
	if (dev->putc)
	dev->putc += gd->reloc_off;
	if (dev->puts)
	dev->puts += gd->reloc_off;
	#endif

	dev->next = serial_devices;
	serial_devices = dev;
	}

	/**
	* serial_initialize() - Register all compiled-in serial port drivers
	*
	* This function registers all serial port drivers that are compiled
	* into the U-Boot binary with the serial core, thus making them
	* available to U-Boot to use. Lastly, this function assigns a default
	* serial port to the serial core. That serial port is then used as a
	* default output.
	*/
	int serial_initialize(void)
	{
	atmel_serial_initialize();
	mcf_serial_initialize();
	mpc85xx_serial_initialize();
	mxc_serial_initialize();
	ns16550_serial_initialize();
	pl01x_serial_initialize();
	pxa_serial_initialize();
	smh_serial_initialize();
	sh_serial_initialize();
	mtk_serial_initialize();

	serial_assign(default_serial_console()->name);

	return 0;
	}

	static int serial_stub_start(struct stdio_dev *sdev)
	{
	struct serial_device *dev = sdev->priv;

	return dev->start();
	}

	static int serial_stub_stop(struct stdio_dev *sdev)
	{
	struct serial_device *dev = sdev->priv;

	return dev->stop();
	}

	static void serial_stub_putc(struct stdio_dev *sdev, const char ch)
	{
	struct serial_device *dev = sdev->priv;

	dev->putc(ch);
	}

	static void serial_stub_puts(struct stdio_dev sdev, const char str)
	{
	struct serial_device *dev = sdev->priv;

	dev->puts(str);
	}

	static int serial_stub_getc(struct stdio_dev *sdev)
	{
	struct serial_device *dev = sdev->priv;

	return dev->getc();
	}

	static int serial_stub_tstc(struct stdio_dev *sdev)
	{
	struct serial_device *dev = sdev->priv;

	return dev->tstc();
	}

	/**
	* serial_stdio_init() - Register serial ports with STDIO core
	*
	* This function generates a proxy driver for each serial port driver.
	* These proxy drivers then register with the STDIO core, making the
	* serial drivers available as STDIO devices.
	*/
	void serial_stdio_init(void)
	{
	struct stdio_dev dev;
	struct serial_device *s = serial_devices;

	while (s) {
	memset(&dev, 0, sizeof(dev));

	strcpy(dev.name, s->name);
	dev.flags = DEV_FLAGS_OUTPUT \| DEV_FLAGS_INPUT;

	dev.start = serial_stub_start;
	dev.stop = serial_stub_stop;
	dev.putc = serial_stub_putc;
	dev.puts = serial_stub_puts;
	dev.getc = serial_stub_getc;
	dev.tstc = serial_stub_tstc;
	dev.priv = s;

	stdio_register(&dev);

	s = s->next;
	}
	}

	/**
	* serial_assign() - Select the serial output device by name
	* @name: Name of the serial driver to be used as default output
	*
	* This function configures the serial output multiplexing by
	* selecting which serial device will be used as default. In case
	* the STDIO "serial" device is selected as stdin/stdout/stderr,
	* the serial device previously configured by this function will be
	* used for the particular operation.
	*
	* Returns 0 on success, negative on error.
	*/
	int serial_assign(const char *name)
	{
	struct serial_device *s;

	for (s = serial_devices; s; s = s->next) {
	if (strcmp(s->name, name))
	continue;
	serial_current = s;
	return 0;
	}

	return -EINVAL;
	}

	/**
	* serial_reinit_all() - Reinitialize all compiled-in serial ports
	*
	* This function reinitializes all serial ports that are compiled
	* into U-Boot by calling their serial_start() functions.
	*/
	void serial_reinit_all(void)
	{
	struct serial_device *s;

	for (s = serial_devices; s; s = s->next)
	s->start();
	}

	/**
	* get_current() - Return pointer to currently selected serial port
	*
	* This function returns a pointer to currently selected serial port.
	* The currently selected serial port is altered by serial_assign()
	* function.
	*
	* In case this function is called before relocation or before any serial
	* port is configured, this function calls default_serial_console() to
	* determine the serial port. Otherwise, the configured serial port is
	* returned.
	*
	* Returns pointer to the currently selected serial port on success,
	* NULL on error.
	*/
	static struct serial_device *get_current(void)
	{
	struct serial_device *dev;

	if (!(gd->flags & GD_FLG_RELOC))
	dev = default_serial_console();
	else if (!serial_current)
	dev = default_serial_console();
	else
	dev = serial_current;

	/* We must have a console device */
	if (!dev) {
	#ifdef CONFIG_SPL_BUILD
	puts("Cannot find console\n");
	hang();
	#else
	panic("Cannot find console\n");
	#endif
	}

	return dev;
	}

	/**
	* serial_init() - Initialize currently selected serial port
	*
	* This function initializes the currently selected serial port. This
	* usually involves setting up the registers of that particular port,
	* enabling clock and such. This function uses the get_current() call
	* to determine which port is selected.
	*
	* Returns 0 on success, negative on error.
	*/
	int serial_init(void)
	{
	gd->flags \|= GD_FLG_SERIAL_READY;
	return get_current()->start();
	}

	/**
	* serial_setbrg() - Configure baud-rate of currently selected serial port
	*
	* This function configures the baud-rate of the currently selected
	* serial port. The baud-rate is retrieved from global data within
	* the serial port driver. This function uses the get_current() call
	* to determine which port is selected.
	*
	* Returns 0 on success, negative on error.
	*/
	void serial_setbrg(void)
	{
	get_current()->setbrg();
	}

	/**
	* serial_getc() - Read character from currently selected serial port
	*
	* This function retrieves a character from currently selected serial
	* port. In case there is no character waiting on the serial port,
	* this function will block and wait for the character to appear. This
	* function uses the get_current() call to determine which port is
	* selected.
	*
	* Returns the character on success, negative on error.
	*/
	int serial_getc(void)
	{
	return get_current()->getc();
	}

	/**
	* serial_tstc() - Test if data is available on currently selected serial port
	*
	* This function tests if one or more characters are available on
	* currently selected serial port. This function never blocks. This
	* function uses the get_current() call to determine which port is
	* selected.
	*
	* Returns positive if character is available, zero otherwise.
	*/
	int serial_tstc(void)
	{
	return get_current()->tstc();
	}

	/**
	* serial_putc() - Output character via currently selected serial port
	* @c: Single character to be output from the serial port.
	*
	* This function outputs a character via currently selected serial
	* port. This character is passed to the serial port driver responsible
	* for controlling the hardware. The hardware may still be in process
	* of transmitting another character, therefore this function may block
	* for a short amount of time. This function uses the get_current()
	* call to determine which port is selected.
	*/
	void serial_putc(const char c)
	{
	get_current()->putc(c);
	}

	/**
	* serial_puts() - Output string via currently selected serial port
	* @s: Zero-terminated string to be output from the serial port.
	*
	* This function outputs a zero-terminated string via currently
	* selected serial port. This function behaves as an accelerator
	* in case the hardware can queue multiple characters for transfer.
	* The whole string that is to be output is available to the function
	* implementing the hardware manipulation. Transmitting the whole
	* string may take some time, thus this function may block for some
	* amount of time. This function uses the get_current() call to
	* determine which port is selected.
	*/
	void serial_puts(const char *s)
	{
	get_current()->puts(s);
	}

	/**
	* default_serial_puts() - Output string by calling serial_putc() in loop
	* @s: Zero-terminated string to be output from the serial port.
	*
	* This function outputs a zero-terminated string by calling serial_putc()
	* in a loop. Most drivers do not support queueing more than one byte for
	* transfer, thus this function precisely implements their serial_puts().
	*
	* To optimize the number of get_current() calls, this function only
	* calls get_current() once and then directly accesses the putc() call
	* of the &struct serial_device .
	*/
	void default_serial_puts(const char *s)
	{
	struct serial_device *dev = get_current();
	while (*s)
	dev->putc(*s++);
	}

	#if CFG_POST & CONFIG_SYS_POST_UART
	static const int bauds[] = CFG_SYS_BAUDRATE_TABLE;

	/**
	* uart_post_test() - Test the currently selected serial port using POST
	* @flags: POST framework flags
	*
	* Do a loopback test of the currently selected serial port. This
	* function is only useful in the context of the POST testing framwork.
	* The serial port is first configured into loopback mode and then
	* characters are sent through it.
	*
	* Returns 0 on success, value otherwise.
	*/
	/* Mark weak until post/cpu/.../uart.c migrate over */
	__weak
	int uart_post_test(int flags)
	{
	unsigned char c;
	int ret, saved_baud, b;
	struct serial_device saved_dev, s;

	/* Save current serial state */
	ret = 0;
	saved_dev = serial_current;
	saved_baud = gd->baudrate;

	for (s = serial_devices; s; s = s->next) {
	/* If this driver doesn't support loop back, skip it */
	if (!s->loop)
	continue;

	/* Test the next device */
	serial_current = s;

	ret = serial_init();
	if (ret)
	goto done;

	/* Consume anything that happens to be queued */
	while (serial_tstc())
	serial_getc();

	/* Enable loop back */
	s->loop(1);

	/* Test every available baud rate */
	for (b = 0; b < ARRAY_SIZE(bauds); ++b) {
	gd->baudrate = bauds[b];
	serial_setbrg();

	/*
	* Stick to printable chars to avoid issues:
	* - terminal corruption
	* - serial program reacting to sequences and sending
	* back random extra data
	* - most serial drivers add in extra chars (like \r\n)
	*/
	for (c = 0x20; c < 0x7f; ++c) {
	/* Send it out */
	serial_putc(c);

	/* Make sure it's the same one */
	ret = (c != serial_getc());
	if (ret) {
	s->loop(0);
	goto done;
	}

	/* Clean up the output in case it was sent */
	serial_putc('\b');
	ret = ('\b' != serial_getc());
	if (ret) {
	s->loop(0);
	goto done;
	}
	}
	}

	/* Disable loop back */
	s->loop(0);

	/* XXX: There is no serial_stop() !? */
	if (s->stop)
	s->stop();
	}

	done:
	/* Restore previous serial state */
	serial_current = saved_dev;
	gd->baudrate = saved_baud;
	serial_reinit_all();
	serial_setbrg();

	return ret;
	}
	#endif