path: root/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/seq_file.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 tty_port		port;
	struct kref		kref;
	struct tty_struct	*tty;
	unsigned int		index;
	unsigned int		opened;
	struct sdio_func	*func;
	struct mutex		func_lock;
	struct task_struct	*in_sdio_uart_irq;
	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->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