sdio: UART/GPS driver

This currently only accepts the GPS class since that's all I have for
testing.  Tested with a Matsushita GPS and gpsd version 2.34.
Signed-off-by: Nicolas Pitre <npitre@mvista.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/card/Kconfig

@@ -32,3 +32,10 @@ config MMC_BLOCK_BOUNCE
 
 	  If unsure, say Y here.
 
+config SDIO_UART
+	tristate "SDIO UART/GPS class support"
+	depends on MMC
+	help
+	  SDIO function driver for SDIO cards that implements the UART
+	  class, as well as the GPS class which appears like a UART.
+

drivers/mmc/card/Makefile

@@ -9,3 +9,5 @@ endif
 obj-$(CONFIG_MMC_BLOCK)		+= mmc_block.o
 mmc_block-objs			:= block.o queue.o
 
+obj-$(CONFIG_SDIO_UART)		+= sdio_uart.o
+

drivers/mmc/card/sdio_uart.c

+/*
+ * linux/drivers/mmc/card/sdio_uart.c - SDIO UART/GPS driver
+ *
+ * Based on drivers/serial/8250.c and drivers/serial/serial_core.c
+ * by Russell King.
+ *
+ * Author:	Nicolas Pitre
+ * Created:	June 15, 2007
+ * Copyright:	MontaVista Software, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ */
+
+/*
+ * Note: Although this driver assumes a 16550A-like UART implementation,
+ * it is not possible to leverage the common 8250/16550 driver, nor the
+ * core UART infrastructure, as they assumes direct access to the hardware
+ * registers, often under a spinlock.  This is not possible in the SDIO
+ * context as SDIO access functions must be able to sleep.
+ *
+ * Because we need to lock the SDIO host to ensure an exclusive access to
+ * the card, we simply rely on that lock to also prevent and serialize
+ * concurrent access to the same port.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+#include <linux/serial_reg.h>
+#include <linux/circ_buf.h>
+#include <linux/gfp.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#include <linux/mmc/core.h>
+#include <linux/mmc/card.h>
+#include <linux/mmc/sdio_func.h>
+#include <linux/mmc/sdio_ids.h>
+
+
+#define UART_NR		8	/* Number of UARTs this driver can handle */
+
+
+#define UART_XMIT_SIZE	PAGE_SIZE
+#define WAKEUP_CHARS	256
+
+#define circ_empty(circ)	((circ)->head == (circ)->tail)
+#define circ_clear(circ)	((circ)->head = (circ)->tail = 0)
+
+#define circ_chars_pending(circ) \
+		(CIRC_CNT((circ)->head, (circ)->tail, UART_XMIT_SIZE))
+
+#define circ_chars_free(circ) \
+		(CIRC_SPACE((circ)->head, (circ)->tail, UART_XMIT_SIZE))
+
+
+struct uart_icount {
+	__u32	cts;
+	__u32	dsr;
+	__u32	rng;
+	__u32	dcd;
+	__u32	rx;
+	__u32	tx;
+	__u32	frame;
+	__u32	overrun;
+	__u32	parity;
+	__u32	brk;
+};
+
+struct sdio_uart_port {
+	struct kref		kref;
+	struct tty_struct	*tty;
+	unsigned int		index;
+	unsigned int		opened;
+	struct mutex		open_lock;
+	struct sdio_func	*func;
+	struct mutex		func_lock;
+	unsigned int		regs_offset;
+	struct circ_buf		xmit;
+	spinlock_t		write_lock;
+	struct uart_icount	icount;
+	unsigned int		uartclk;
+	unsigned int		mctrl;
+	unsigned int		read_status_mask;
+	unsigned int		ignore_status_mask;
+	unsigned char		x_char;
+	unsigned char           ier;
+	unsigned char           lcr;
+};
+
+static struct sdio_uart_port *sdio_uart_table[UART_NR];
+static DEFINE_SPINLOCK(sdio_uart_table_lock);
+
+static int sdio_uart_add_port(struct sdio_uart_port *port)
+{
+	int index, ret = -EBUSY;
+
+	kref_init(&port->kref);
+	mutex_init(&port->open_lock);
+	mutex_init(&port->func_lock);
+	spin_lock_init(&port->write_lock);
+
+	spin_lock(&sdio_uart_table_lock);
+	for (index = 0; index < UART_NR; index++) {
+		if (!sdio_uart_table[index]) {
+			port->index = index;
+			sdio_uart_table[index] = port;
+			ret = 0;
+			break;
+		}
+	}
+	spin_unlock(&sdio_uart_table_lock);
+
+	return ret;
+}
+
+static struct sdio_uart_port *sdio_uart_port_get(unsigned index)
+{
+	struct sdio_uart_port *port;
+
+	if (index >= UART_NR)
+		return NULL;
+
+	spin_lock(&sdio_uart_table_lock);
+	port = sdio_uart_table[index];
+	if (port)
+		kref_get(&port->kref);
+	spin_unlock(&sdio_uart_table_lock);
+
+	return port;
+}
+
+static void sdio_uart_port_destroy(struct kref *kref)
+{
+	struct sdio_uart_port *port =
+		container_of(kref, struct sdio_uart_port, kref);
+	kfree(port);
+}
+
+static void sdio_uart_port_put(struct sdio_uart_port *port)
+{
+	kref_put(&port->kref, sdio_uart_port_destroy);
+}
+
+static void sdio_uart_port_remove(struct sdio_uart_port *port)
+{
+	struct sdio_func *func;
+
+	BUG_ON(sdio_uart_table[port->index] != port);
+
+	spin_lock(&sdio_uart_table_lock);
+	sdio_uart_table[port->index] = NULL;
+	spin_unlock(&sdio_uart_table_lock);
+
+	/*
+	 * We're killing a port that potentially still is in use by
+	 * the tty layer. Be careful to prevent any further access
+	 * to the SDIO function and arrange for the tty layer to
+	 * give up on that port ASAP.
+	 * Beware: the lock ordering is critical.
+	 */
+	mutex_lock(&port->open_lock);
+	mutex_lock(&port->func_lock);
+	func = port->func;
+	sdio_claim_host(func);
+	port->func = NULL;
+	mutex_unlock(&port->func_lock);
+	if (port->opened)
+		tty_hangup(port->tty);
+	mutex_unlock(&port->open_lock);
+	sdio_release_irq(func);
+	sdio_disable_func(func);
+	sdio_release_host(func);
+
+	sdio_uart_port_put(port);
+}
+
+static int sdio_uart_claim_func(struct sdio_uart_port *port)
+{
+	mutex_lock(&port->func_lock);
+	if (unlikely(!port->func)) {
+		mutex_unlock(&port->func_lock);
+		return -ENODEV;
+	}
+	sdio_claim_host(port->func);
+	mutex_unlock(&port->func_lock);
+	return 0;
+}
+
+static inline void sdio_uart_release_func(struct sdio_uart_port *port)
+{
+	sdio_release_host(port->func);
+}
+
+static inline unsigned int sdio_in(struct sdio_uart_port *port, int offset)
+{
+	unsigned char c;
+	c = sdio_readb(port->func, port->regs_offset + offset, NULL);
+	return c;
+}
+
+static inline void sdio_out(struct sdio_uart_port *port, int offset, int value)
+{
+	sdio_writeb(port->func, value, port->regs_offset + offset, NULL);
+}
+
+static unsigned int sdio_uart_get_mctrl(struct sdio_uart_port *port)
+{
+	unsigned char status;
+	unsigned int ret;
+
+	status = sdio_in(port, UART_MSR);
+
+	ret = 0;
+	if (status & UART_MSR_DCD)
+		ret |= TIOCM_CAR;
+	if (status & UART_MSR_RI)
+		ret |= TIOCM_RNG;
+	if (status & UART_MSR_DSR)
+		ret |= TIOCM_DSR;
+	if (status & UART_MSR_CTS)
+		ret |= TIOCM_CTS;
+	return ret;
+}
+
+static void sdio_uart_write_mctrl(struct sdio_uart_port *port, unsigned int mctrl)
+{
+	unsigned char mcr = 0;
+
+	if (mctrl & TIOCM_RTS)
+		mcr |= UART_MCR_RTS;
+	if (mctrl & TIOCM_DTR)
+		mcr |= UART_MCR_DTR;
+	if (mctrl & TIOCM_OUT1)
+		mcr |= UART_MCR_OUT1;
+	if (mctrl & TIOCM_OUT2)
+		mcr |= UART_MCR_OUT2;
+	if (mctrl & TIOCM_LOOP)
+		mcr |= UART_MCR_LOOP;
+
+	sdio_out(port, UART_MCR, mcr);
+}
+
+static inline void sdio_uart_update_mctrl(struct sdio_uart_port *port,
+					  unsigned int set, unsigned int clear)
+{
+	unsigned int old;
+
+	old = port->mctrl;
+	port->mctrl = (old & ~clear) | set;
+	if (old != port->mctrl)
+		sdio_uart_write_mctrl(port, port->mctrl);
+}
+
+#define sdio_uart_set_mctrl(port, x)	sdio_uart_update_mctrl(port, x, 0)
+#define sdio_uart_clear_mctrl(port, x)	sdio_uart_update_mctrl(port, 0, x)
+
+static void sdio_uart_change_speed(struct sdio_uart_port *port,
+				   struct ktermios *termios,
+				   struct ktermios *old)
+{
+	unsigned char cval, fcr = 0;
+	unsigned int baud, quot;
+
+	switch (termios->c_cflag & CSIZE) {
+	case CS5:
+		cval = UART_LCR_WLEN5;
+		break;
+	case CS6:
+		cval = UART_LCR_WLEN6;
+		break;
+	case CS7:
+		cval = UART_LCR_WLEN7;
+		break;
+	default:
+	case CS8:
+		cval = UART_LCR_WLEN8;
+		break;
+	}
+
+	if (termios->c_cflag & CSTOPB)
+		cval |= UART_LCR_STOP;
+	if (termios->c_cflag & PARENB)
+		cval |= UART_LCR_PARITY;
+	if (!(termios->c_cflag & PARODD))
+		cval |= UART_LCR_EPAR;
+
+	for (;;) {
+		baud = tty_termios_baud_rate(termios);
+		if (baud == 0)
+			baud = 9600;  /* Special case: B0 rate. */
+		if (baud <= port->uartclk)
+			break;
+		/*
+		 * Oops, the quotient was zero.  Try again with the old
+		 * baud rate if possible, otherwise default to 9600.
+		 */
+		termios->c_cflag &= ~CBAUD;
+		if (old) {
+			termios->c_cflag |= old->c_cflag & CBAUD;
+			old = NULL;
+		} else
+			termios->c_cflag |= B9600;
+	}
+	quot = (2 * port->uartclk + baud) / (2 * baud);
+
+	if (baud < 2400)
+		fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_1;
+	else
+		fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
+
+	port->read_status_mask = UART_LSR_OE | UART_LSR_THRE | UART_LSR_DR;
+	if (termios->c_iflag & INPCK)
+		port->read_status_mask |= UART_LSR_FE | UART_LSR_PE;
+	if (termios->c_iflag & (BRKINT | PARMRK))
+		port->read_status_mask |= UART_LSR_BI;
+
+	/*
+	 * Characters to ignore
+	 */
+	port->ignore_status_mask = 0;
+	if (termios->c_iflag & IGNPAR)
+		port->ignore_status_mask |= UART_LSR_PE | UART_LSR_FE;
+	if (termios->c_iflag & IGNBRK) {
+		port->ignore_status_mask |= UART_LSR_BI;
+		/*
+		 * If we're ignoring parity and break indicators,
+		 * ignore overruns too (for real raw support).
+		 */
+		if (termios->c_iflag & IGNPAR)
+			port->ignore_status_mask |= UART_LSR_OE;
+	}
+
+	/*
+	 * ignore all characters if CREAD is not set
+	 */
+	if ((termios->c_cflag & CREAD) == 0)
+		port->ignore_status_mask |= UART_LSR_DR;
+
+	/*
+	 * CTS flow control flag and modem status interrupts
+	 */
+	port->ier &= ~UART_IER_MSI;
+	if ((termios->c_cflag & CRTSCTS) || !(termios->c_cflag & CLOCAL))
+		port->ier |= UART_IER_MSI;
+
+	port->lcr = cval;
+
+	sdio_out(port, UART_IER, port->ier);
+	sdio_out(port, UART_LCR, cval | UART_LCR_DLAB);
+	sdio_out(port, UART_DLL, quot & 0xff);
+	sdio_out(port, UART_DLM, quot >> 8);
+	sdio_out(port, UART_LCR, cval);
+	sdio_out(port, UART_FCR, fcr);
+
+	sdio_uart_write_mctrl(port, port->mctrl);
+}
+
+static void sdio_uart_start_tx(struct sdio_uart_port *port)
+{
+	if (!(port->ier & UART_IER_THRI)) {
+		port->ier |= UART_IER_THRI;
+		sdio_out(port, UART_IER, port->ier);
+	}
+}
+
+static void sdio_uart_stop_tx(struct sdio_uart_port *port)
+{
+	if (port->ier & UART_IER_THRI) {
+		port->ier &= ~UART_IER_THRI;
+		sdio_out(port, UART_IER, port->ier);
+	}
+}
+
+static void sdio_uart_stop_rx(struct sdio_uart_port *port)
+{
+	port->ier &= ~UART_IER_RLSI;
+	port->read_status_mask &= ~UART_LSR_DR;
+	sdio_out(port, UART_IER, port->ier);
+}
+
+static void sdio_uart_receive_chars(struct sdio_uart_port *port, int *status)
+{
+	struct tty_struct *tty = port->tty;
+	unsigned int ch, flag;
+	int max_count = 256;
+
+	do {
+		ch = sdio_in(port, UART_RX);
+		flag = TTY_NORMAL;
+		port->icount.rx++;
+
+		if (unlikely(*status & (UART_LSR_BI | UART_LSR_PE |
+				        UART_LSR_FE | UART_LSR_OE))) {
+			/*
+			 * For statistics only
+			 */
+			if (*status & UART_LSR_BI) {
+				*status &= ~(UART_LSR_FE | UART_LSR_PE);
+				port->icount.brk++;
+			} else if (*status & UART_LSR_PE)
+				port->icount.parity++;
+			else if (*status & UART_LSR_FE)
+				port->icount.frame++;
+			if (*status & UART_LSR_OE)
+				port->icount.overrun++;
+
+			/*
+			 * Mask off conditions which should be ignored.
+			 */
+			*status &= port->read_status_mask;
+			if (*status & UART_LSR_BI) {
+				flag = TTY_BREAK;
+			} else if (*status & UART_LSR_PE)
+				flag = TTY_PARITY;
+			else if (*status & UART_LSR_FE)
+				flag = TTY_FRAME;
+		}
+
+		if ((*status & port->ignore_status_mask & ~UART_LSR_OE) == 0)
+			tty_insert_flip_char(tty, ch, flag);
+
+		/*
+		 * Overrun is special.  Since it's reported immediately,
+		 * it doesn't affect the current character.
+		 */
+		if (*status & ~port->ignore_status_mask & UART_LSR_OE)
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
+
+		*status = sdio_in(port, UART_LSR);
+	} while ((*status & UART_LSR_DR) && (max_count-- > 0));
+	tty_flip_buffer_push(tty);
+}
+
+static void sdio_uart_transmit_chars(struct sdio_uart_port *port)
+{
+	struct circ_buf *xmit = &port->xmit;
+	int count;
+
+	if (port->x_char) {
+		sdio_out(port, UART_TX, port->x_char);
+		port->icount.tx++;
+		port->x_char = 0;
+		return;
+	}
+	if (circ_empty(xmit) || port->tty->stopped || port->tty->hw_stopped) {
+		sdio_uart_stop_tx(port);
+		return;
+	}
+
+	count = 16;
+	do {
+		sdio_out(port, UART_TX, xmit->buf[xmit->tail]);
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		port->icount.tx++;
+		if (circ_empty(xmit))
+			break;
+	} while (--count > 0);
+
+	if (circ_chars_pending(xmit) < WAKEUP_CHARS)
+		tty_wakeup(port->tty);
+
+	if (circ_empty(xmit))
+		sdio_uart_stop_tx(port);
+}
+
+static void sdio_uart_check_modem_status(struct sdio_uart_port *port)
+{
+	int status;
+
+	status = sdio_in(port, UART_MSR);
+
+	if ((status & UART_MSR_ANY_DELTA) == 0)
+		return;
+
+	if (status & UART_MSR_TERI)
+		port->icount.rng++;
+	if (status & UART_MSR_DDSR)
+		port->icount.dsr++;
+	if (status & UART_MSR_DDCD)
+		port->icount.dcd++;
+	if (status & UART_MSR_DCTS) {
+		port->icount.cts++;
+		if (port->tty->termios->c_cflag & CRTSCTS) {
+			int cts = (status & UART_MSR_CTS);
+			if (port->tty->hw_stopped) {
+				if (cts) {
+					port->tty->hw_stopped = 0;
+					sdio_uart_start_tx(port);
+					tty_wakeup(port->tty);
+				}
+			} else {
+				if (!cts) {
+					port->tty->hw_stopped = 1;
+					sdio_uart_stop_tx(port);
+				}
+			}
+		}
+	}
+}
+
+/*
+ * This handles the interrupt from one port.
+ */
+static void sdio_uart_irq(struct sdio_func *func)
+{
+	struct sdio_uart_port *port = sdio_get_drvdata(func);
+	unsigned int iir, lsr;
+
+	iir = sdio_in(port, UART_IIR);
+	if (iir & UART_IIR_NO_INT)
+		return;
+	lsr = sdio_in(port, UART_LSR);
+	if (lsr & UART_LSR_DR)
+		sdio_uart_receive_chars(port, &lsr);
+	sdio_uart_check_modem_status(port);
+	if (lsr & UART_LSR_THRE)
+		sdio_uart_transmit_chars(port);
+}
+
+static int sdio_uart_startup(struct sdio_uart_port *port)
+{
+	unsigned long page;
+	int ret;
+
+	/*
+	 * Set the TTY IO error marker - we will only clear this
+	 * once we have successfully opened the port.
+	 */
+	set_bit(TTY_IO_ERROR, &port->tty->flags);
+
+	/* Initialise and allocate the transmit buffer. */
+	page = __get_free_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+	port->xmit.buf = (unsigned char *)page;
+	circ_clear(&port->xmit);
+
+	ret = sdio_uart_claim_func(port);
+	if (ret)
+		goto err1;
+	ret = sdio_enable_func(port->func);
+	if (ret)
+		goto err2;
+	ret = sdio_claim_irq(port->func, sdio_uart_irq);
+	if (ret)
+		goto err3;
+
+	/*
+	 * Clear the FIFO buffers and disable them.
+	 * (they will be reenabled in sdio_change_speed())
+	 */
+	sdio_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
+	sdio_out(port, UART_FCR, UART_FCR_ENABLE_FIFO |
+			UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
+	sdio_out(port, UART_FCR, 0);
+
+	/*
+	 * Clear the interrupt registers.
+	 */
+	(void) sdio_in(port, UART_LSR);
+	(void) sdio_in(port, UART_RX);
+	(void) sdio_in(port, UART_IIR);
+	(void) sdio_in(port, UART_MSR);
+
+	/*
+	 * Now, initialize the UART
+	 */
+	sdio_out(port, UART_LCR, UART_LCR_WLEN8);
+
+	port->ier = UART_IER_RLSI | UART_IER_RDI | UART_IER_RTOIE | UART_IER_UUE;
+	port->mctrl = TIOCM_OUT2;
+
+	sdio_uart_change_speed(port, port->tty->termios, NULL);
+
+	if (port->tty->termios->c_cflag & CBAUD)
+		sdio_uart_set_mctrl(port, TIOCM_RTS | TIOCM_DTR);
+
+	if (port->tty->termios->c_cflag & CRTSCTS)
+		if (!(sdio_uart_get_mctrl(port) & TIOCM_CTS))
+			port->tty->hw_stopped = 1;
+
+	clear_bit(TTY_IO_ERROR, &port->tty->flags);
+
+	/* Kick the IRQ handler once while we're still holding the host lock */
+	sdio_uart_irq(port->func);
+
+	sdio_uart_release_func(port);
+	return 0;
+
+err3:
+	sdio_disable_func(port->func);
+err2:
+	sdio_uart_release_func(port);
+err1:
+	free_page((unsigned long)port->xmit.buf);
+	return ret;
+}
+
+static void sdio_uart_shutdown(struct sdio_uart_port *port)
+{
+	int ret;
+
+	ret = sdio_uart_claim_func(port);
+	if (ret)
+		goto skip;
+
+	sdio_uart_stop_rx(port);
+
+	/* TODO: wait here for TX FIFO to drain */
+
+	/* Turn off DTR and RTS early. */
+	if (port->tty->termios->c_cflag & HUPCL)
+		sdio_uart_clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
+
+	 /* Disable interrupts from this port */
+	sdio_release_irq(port->func);
+	port->ier = 0;
+	sdio_out(port, UART_IER, 0);
+
+	sdio_uart_clear_mctrl(port, TIOCM_OUT2);
+
+	/* Disable break condition and FIFOs. */
+	port->lcr &= ~UART_LCR_SBC;
+	sdio_out(port, UART_LCR, port->lcr);
+	sdio_out(port, UART_FCR, UART_FCR_ENABLE_FIFO |
+				 UART_FCR_CLEAR_RCVR |
+				 UART_FCR_CLEAR_XMIT);
+	sdio_out(port, UART_FCR, 0);
+
+	sdio_disable_func(port->func);
+
+	sdio_uart_release_func(port);
+
+skip:
+	/* Free the transmit buffer page. */
+	free_page((unsigned long)port->xmit.buf);
+}
+
+static int sdio_uart_open (struct tty_struct *tty, struct file * filp)
+{
+	struct sdio_uart_port *port;
+	int ret;
+
+	port = sdio_uart_port_get(tty->index);
+	if (!port)
+		return -ENODEV;
+
+	mutex_lock(&port->open_lock);
+
+	/*
+	 * Make sure not to mess up with a dead port
+	 * which has not been closed yet.
+	 */
+	if (tty->driver_data && tty->driver_data != port) {
+		mutex_unlock(&port->open_lock);
+		sdio_uart_port_put(port);
+		return -EBUSY;
+	}
+
+	if (!port->opened) {
+		tty->driver_data = port;
+		port->tty = tty;
+		ret = sdio_uart_startup(port);
+		if (ret) {
+			tty->driver_data = NULL;
+			port->tty = NULL;
+			mutex_unlock(&port->open_lock);
+			sdio_uart_port_put(port);
+			return ret;
+		}
+	}
+	port->opened++;
+	mutex_unlock(&port->open_lock);
+	return 0;
+}
+
+static void sdio_uart_close(struct tty_struct *tty, struct file * filp)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+
+	if (!port)
+		return;
+
+	mutex_lock(&port->open_lock);
+	BUG_ON(!port->opened);
+
+	/*
+	 * This is messy.  The tty layer calls us even when open()
+	 * returned an error.  Ignore this close request if tty->count
+	 * is larger than port->count.
+	 */
+	if (tty->count > port->opened) {
+		mutex_unlock(&port->open_lock);
+		return;
+	}
+
+	if (--port->opened == 0) {
+		tty->closing = 1;
+		sdio_uart_shutdown(port);
+		tty_ldisc_flush(tty);
+		port->tty = NULL;
+		tty->driver_data = NULL;
+		tty->closing = 0;
+	}
+	mutex_unlock(&port->open_lock);
+	sdio_uart_port_put(port);
+}
+
+static int sdio_uart_write(struct tty_struct * tty, const unsigned char *buf,
+			   int count)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+	struct circ_buf *circ = &port->xmit;
+	int c, ret = 0;
+
+	if (!port->func)
+		return -ENODEV;
+
+	spin_lock(&port->write_lock);
+	while (1) {
+		c = CIRC_SPACE_TO_END(circ->head, circ->tail, UART_XMIT_SIZE);
+		if (count < c)
+			c = count;
+		if (c <= 0)
+			break;
+		memcpy(circ->buf + circ->head, buf, c);
+		circ->head = (circ->head + c) & (UART_XMIT_SIZE - 1);
+		buf += c;
+		count -= c;
+		ret += c;
+	}
+	spin_unlock(&port->write_lock);
+
+	if ( !(port->ier & UART_IER_THRI)) {
+		int err = sdio_uart_claim_func(port);
+		if (!err) {
+			sdio_uart_start_tx(port);
+			sdio_uart_irq(port->func);
+			sdio_uart_release_func(port);
+		} else
+			ret = err;
+	}
+
+	return ret;
+}
+
+static int sdio_uart_write_room(struct tty_struct *tty)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+	return port ? circ_chars_free(&port->xmit) : 0;
+}
+
+static int sdio_uart_chars_in_buffer(struct tty_struct *tty)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+	return port ? circ_chars_pending(&port->xmit) : 0;
+}
+
+static void sdio_uart_send_xchar(struct tty_struct *tty, char ch)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+
+	port->x_char = ch;
+	if (ch && !(port->ier & UART_IER_THRI)) {
+		if (sdio_uart_claim_func(port) != 0)
+			return;
+		sdio_uart_start_tx(port);
+		sdio_uart_irq(port->func);
+		sdio_uart_release_func(port);
+	}
+}
+
+static void sdio_uart_throttle(struct tty_struct *tty)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+
+	if (!I_IXOFF(tty) && !(tty->termios->c_cflag & CRTSCTS))
+		return;
+
+	if (sdio_uart_claim_func(port) != 0)
+		return;
+
+	if (I_IXOFF(tty)) {
+		port->x_char = STOP_CHAR(tty);
+		sdio_uart_start_tx(port);
+	}
+
+	if (tty->termios->c_cflag & CRTSCTS)
+		sdio_uart_clear_mctrl(port, TIOCM_RTS);
+
+	sdio_uart_irq(port->func);
+	sdio_uart_release_func(port);
+}
+
+static void sdio_uart_unthrottle(struct tty_struct *tty)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+
+	if (!I_IXOFF(tty) && !(tty->termios->c_cflag & CRTSCTS))
+		return;
+
+	if (sdio_uart_claim_func(port) != 0)
+		return;
+
+	if (I_IXOFF(tty)) {
+		if (port->x_char) {
+			port->x_char = 0;
+		} else {
+			port->x_char = START_CHAR(tty);
+			sdio_uart_start_tx(port);
+		}
+	}
+
+	if (tty->termios->c_cflag & CRTSCTS)
+		sdio_uart_set_mctrl(port, TIOCM_RTS);
+
+	sdio_uart_irq(port->func);
+	sdio_uart_release_func(port);
+}
+
+static void sdio_uart_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+	unsigned int cflag = tty->termios->c_cflag;
+
+#define RELEVANT_IFLAG(iflag)   ((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))
+
+	if ((cflag ^ old_termios->c_cflag) == 0 &&
+	    RELEVANT_IFLAG(tty->termios->c_iflag ^ old_termios->c_iflag) == 0)
+		return;
+
+	if (sdio_uart_claim_func(port) != 0)
+		return;
+
+	sdio_uart_change_speed(port, tty->termios, old_termios);
+
+	/* Handle transition to B0 status */
+	if ((old_termios->c_cflag & CBAUD) && !(cflag & CBAUD))
+		sdio_uart_clear_mctrl(port, TIOCM_RTS | TIOCM_DTR);
+
+	/* Handle transition away from B0 status */
+	if (!(old_termios->c_cflag & CBAUD) && (cflag & CBAUD)) {
+		unsigned int mask = TIOCM_DTR;
+		if (!(cflag & CRTSCTS) || !test_bit(TTY_THROTTLED, &tty->flags))
+			mask |= TIOCM_RTS;
+		sdio_uart_set_mctrl(port, mask);
+	}
+
+	/* Handle turning off CRTSCTS */
+	if ((old_termios->c_cflag & CRTSCTS) && !(cflag & CRTSCTS)) {
+		tty->hw_stopped = 0;
+		sdio_uart_start_tx(port);
+	}
+
+	/* Handle turning on CRTSCTS */
+	if (!(old_termios->c_cflag & CRTSCTS) && (cflag & CRTSCTS)) {
+		if (!(sdio_uart_get_mctrl(port) & TIOCM_CTS)) {
+			tty->hw_stopped = 1;
+			sdio_uart_stop_tx(port);
+		}
+	}
+
+	sdio_uart_release_func(port);
+}
+
+static void sdio_uart_break_ctl(struct tty_struct *tty, int break_state)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+
+	if (sdio_uart_claim_func(port) != 0)
+		return;
+
+	if (break_state == -1)
+		port->lcr |= UART_LCR_SBC;
+	else
+		port->lcr &= ~UART_LCR_SBC;
+	sdio_out(port, UART_LCR, port->lcr);
+
+	sdio_uart_release_func(port);
+}
+
+static int sdio_uart_tiocmget(struct tty_struct *tty, struct file *file)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+	int result;
+
+	result = sdio_uart_claim_func(port);
+	if (!result) {
+		result = port->mctrl | sdio_uart_get_mctrl(port);
+		sdio_uart_release_func(port);
+	}
+
+	return result;
+}
+
+static int sdio_uart_tiocmset(struct tty_struct *tty, struct file *file,
+			      unsigned int set, unsigned int clear)
+{
+	struct sdio_uart_port *port = tty->driver_data;
+	int result;
+
+	result =sdio_uart_claim_func(port);
+	if(!result) {
+		sdio_uart_update_mctrl(port, set, clear);
+		sdio_uart_release_func(port);
+	}
+
+	return result;
+}
+
+static const struct tty_operations sdio_uart_ops = {
+	.open			= sdio_uart_open,
+	.close			= sdio_uart_close,
+	.write			= sdio_uart_write,
+	.write_room		= sdio_uart_write_room,
+	.chars_in_buffer	= sdio_uart_chars_in_buffer,
+	.send_xchar		= sdio_uart_send_xchar,
+	.throttle		= sdio_uart_throttle,
+	.unthrottle		= sdio_uart_unthrottle,
+	.set_termios		= sdio_uart_set_termios,
+	.break_ctl		= sdio_uart_break_ctl,
+	.tiocmget		= sdio_uart_tiocmget,
+	.tiocmset		= sdio_uart_tiocmset,
+};
+
+static struct tty_driver *sdio_uart_tty_driver;
+
+static int sdio_uart_probe(struct sdio_func *func,
+			   const struct sdio_device_id *id)
+{
+	struct sdio_uart_port *port;
+	int ret;
+
+	port = kzalloc(sizeof(struct sdio_uart_port), GFP_KERNEL);
+	if (!port)
+		return -ENOMEM;
+
+	if (func->class == SDIO_CLASS_UART) {
+		printk(KERN_WARNING "%s: need info on UART class basic setup\n",
+		       sdio_func_id(func));
+		kfree(port);
+		return -ENOSYS;
+	} else if (func->class == SDIO_CLASS_GPS) {
+		/*
+		 * We need tuple 0x91.  It contains SUBTPL_SIOREG
+		 * and SUBTPL_RCVCAPS.
+		 */
+		struct sdio_func_tuple *tpl;
+		for (tpl = func->tuples; tpl; tpl = tpl->next) {
+			if (tpl->code != 0x91)
+				continue;
+			if (tpl->size < 10)
+				continue;
+			if (tpl->data[1] == 0)  /* SUBTPL_SIOREG */
+				break;
+		}
+		if (!tpl) {
+			printk(KERN_WARNING
+			       "%s: can't find tuple 0x91 subtuple 0 (SUBTPL_SIOREG) for GPS class\n",
+			       sdio_func_id(func));
+			kfree(port);
+			return -EINVAL;
+		}
+		printk(KERN_DEBUG "%s: Register ID = 0x%02x, Exp ID = 0x%02x\n",
+		       sdio_func_id(func), tpl->data[2], tpl->data[3]);
+		port->regs_offset = (tpl->data[4] << 0) |
+				    (tpl->data[5] << 8) |
+				    (tpl->data[6] << 16);
+		printk(KERN_DEBUG "%s: regs offset = 0x%x\n",
+		       sdio_func_id(func), port->regs_offset);
+		port->uartclk = tpl->data[7] * 115200;
+		if (port->uartclk == 0)
+			port->uartclk = 115200;
+		printk(KERN_DEBUG "%s: clk %d baudcode %u 4800-div %u\n",
+		       sdio_func_id(func), port->uartclk,
+		       tpl->data[7], tpl->data[8] | (tpl->data[9] << 8));
+	} else {
+		kfree(port);
+		return -EINVAL;
+	}
+
+	port->func = func;
+	sdio_set_drvdata(func, port);
+
+	ret = sdio_uart_add_port(port);
+	if (ret) {
+		kfree(port);
+	} else {
+		struct device *dev;
+		dev = tty_register_device(sdio_uart_tty_driver, port->index, &func->dev);
+		if (IS_ERR(dev)) {
+			sdio_uart_port_remove(port);
+			ret = PTR_ERR(dev);
+		}
+	}
+
+	return ret;
+}
+
+static void sdio_uart_remove(struct sdio_func *func)
+{
+	struct sdio_uart_port *port = sdio_get_drvdata(func);
+
+	tty_unregister_device(sdio_uart_tty_driver, port->index);
+	sdio_uart_port_remove(port);
+}
+
+static const struct sdio_device_id sdio_uart_ids[] = {
+	{ SDIO_DEVICE_CLASS(SDIO_CLASS_UART)		},
+	{ SDIO_DEVICE_CLASS(SDIO_CLASS_GPS)		},
+	{ /* end: all zeroes */				},
+};
+
+MODULE_DEVICE_TABLE(sdio, sdio_uart_ids);
+
+static struct sdio_driver sdio_uart_driver = {
+	.probe		= sdio_uart_probe,
+	.remove		= sdio_uart_remove,
+	.name		= "sdio_uart",
+	.id_table	= sdio_uart_ids,
+};
+
+static int __init sdio_uart_init(void)
+{
+	int ret;
+	struct tty_driver *tty_drv;
+
+	sdio_uart_tty_driver = tty_drv = alloc_tty_driver(UART_NR);
+	if (!tty_drv)
+		return -ENOMEM;
+
+	tty_drv->owner = THIS_MODULE;
+	tty_drv->driver_name = "sdio_uart";
+	tty_drv->name =   "ttySDIO";
+	tty_drv->major = 0;  /* dynamically allocated */
+	tty_drv->minor_start = 0;
+	tty_drv->type = TTY_DRIVER_TYPE_SERIAL;
+	tty_drv->subtype = SERIAL_TYPE_NORMAL;
+	tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
+	tty_drv->init_termios = tty_std_termios;
+	tty_drv->init_termios.c_cflag = B4800 | CS8 | CREAD | HUPCL | CLOCAL;
+	tty_set_operations(tty_drv, &sdio_uart_ops);
+
+	ret = tty_register_driver(tty_drv);
+	if (ret)
+		goto err1;
+
+	ret = sdio_register_driver(&sdio_uart_driver);
+	if (ret)
+		goto err2;
+
+	return 0;
+
+err2:
+	tty_unregister_driver(tty_drv);
+err1:
+	put_tty_driver(tty_drv);
+	return ret;
+}
+
+static void __exit sdio_uart_exit(void)
+{
+	sdio_unregister_driver(&sdio_uart_driver);
+	tty_unregister_driver(sdio_uart_tty_driver);
+	put_tty_driver(sdio_uart_tty_driver);
+}
+
+module_init(sdio_uart_init);
+module_exit(sdio_uart_exit);
+
+MODULE_AUTHOR("Nicolas Pitre");
+MODULE_LICENSE("GPL");