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>

1 files changed, 1077 insertions, 0 deletions

diff --git a/drivers/mmc/card/sdio_uart.c b/drivers/mmc/card/sdio_uart.c
new file mode 100644
index 000000000000..e4d9e85ff584
--- /dev/null
+++ b/drivers/mmc/card/sdio_uart.c
@@ -0,0 +1,1077 @@
+/*
+ * 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");