path: root/drivers/mmc/core/sdio_uart.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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.
 */

/*
 * 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/sched.h>
#include <linux/mutex.h>
#include <linux/seq_file.h>
#include <linux/serial.h>
#include <linux/serial_reg.h>
#include <linux/circ_buf.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/kfifo.h>
#include <linux/slab.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 FIFO_SIZE	PAGE_SIZE
#define WAKEUP_CHARS	256

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;
	unsigned int		index;
	struct sdio_func	*func;
	struct mutex		func_lock;
	struct task_struct	*in_sdio_uart_irq;
	unsigned int		regs_offset;
	struct kfifo		xmit_fifo;
	spinlock_t		write_lock;
	struct uart_icount	icount;
	unsigned int		uartclk;
	unsigned int		mctrl;
	unsigned int		rx_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;

	mutex_init(&port->func_lock);
	spin_lock_init(&port->write_lock);
	if (kfifo_alloc(&port->xmit_fifo, FIFO_SIZE, GFP_KERNEL))
		return -ENOMEM;

	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)
		tty_port_get(&port->port);
	spin_unlock(&sdio_uart_table_lock);

	return port;
}

static void sdio_uart_port_put(struct sdio_uart_port *port)
{
	tty_port_put(&port->port);
}

static void sdio_uart_port_remove(struct sdio_uart_port *port)
{
	struct sdio_func *func;

	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->port.mutex);
	mutex_lock(&port->func_lock);
	func = port->func;
	sdio_claim_host(func);
	port->func = NULL;
	mutex_unlock(&port->func_lock);
	/* tty_hangup is async so is this safe as is ?? */
	tty_port_tty_hangup(&port->port, false);
	mutex_unlock(&port->port.mutex);
	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(