path: root/drivers/staging/greybus/uart.c

// SPDX-License-Identifier: GPL-2.0
/*
 * UART driver for the Greybus "generic" UART module.
 *
 * Copyright 2014 Google Inc.
 * Copyright 2014 Linaro Ltd.
 *
 * Heavily based on drivers/usb/class/cdc-acm.c and
 * drivers/usb/serial/usb-serial.c.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched/signal.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/mutex.h>
#include <linux/tty.h>
#include <linux/serial.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/idr.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/kfifo.h>
#include <linux/workqueue.h>
#include <linux/completion.h>
#include <linux/greybus.h>

#include "gbphy.h"

#define GB_NUM_MINORS	16	/* 16 is more than enough */
#define GB_NAME		"ttyGB"

#define GB_UART_WRITE_FIFO_SIZE		PAGE_SIZE
#define GB_UART_WRITE_ROOM_MARGIN	1	/* leave some space in fifo */
#define GB_UART_FIRMWARE_CREDITS	4096
#define GB_UART_CREDIT_WAIT_TIMEOUT_MSEC	10000

struct gb_tty {
	struct gbphy_device *gbphy_dev;
	struct tty_port port;
	void *buffer;
	size_t buffer_payload_max;
	struct gb_connection *connection;
	u16 cport_id;
	unsigned int minor;
	unsigned char clocal;
	bool disconnected;
	spinlock_t read_lock;
	spinlock_t write_lock;
	struct async_icount iocount;
	struct async_icount oldcount;
	wait_queue_head_t wioctl;
	struct mutex mutex;
	u8 ctrlin;	/* input control lines */
	u8 ctrlout;	/* output control lines */
	struct gb_uart_set_line_coding_request line_coding;
	struct work_struct tx_work;
	struct kfifo write_fifo;
	bool close_pending;
	unsigned int credits;
	struct completion credits_complete;
};

static struct tty_driver *gb_tty_driver;
static DEFINE_IDR(tty_minors);
static DEFINE_MUTEX(table_lock);

static int gb_uart_receive_data_handler(struct gb_operation *op)
{
	struct gb_connection *connection = op->connection;
	struct gb_tty *gb_tty = gb_connection_get_data(connection);
	struct tty_port *port = &gb_tty->port;
	struct gb_message *request = op->request;
	struct gb_uart_recv_data_request *receive_data;
	u16 recv_data_size;
	int count;
	unsigned long tty_flags = TTY_NORMAL;

	if (request->payload_size < sizeof(*receive_data)) {
		dev_err(&gb_tty->gbphy_dev->dev,
			"short receive-data request received (%zu < %zu)\n",
			request->payload_size, sizeof(*receive_data));
		return -EINVAL;
	}

	receive_data = op->request->payload;
	recv_data_size = le16_to_cpu(receive_data->size);

	if (recv_data_size != request->payload_size - sizeof(*receive_data)) {
		dev_err(&gb_tty->gbphy_dev->dev,
			"malformed receive-data request received (%u != %zu)\n",
			recv_data_size,
			request->payload_size - sizeof(*receive_data));
		return -EINVAL;
	}

	if (!recv_data_size)
		return -EINVAL;

	if (receive_data->flags) {
		if (receive_data->flags & GB_UART_RECV_FLAG_BREAK)
			tty_flags = TTY_BREAK;
		else if (receive_data->flags & GB_UART_RECV_FLAG_PARITY)
			tty_flags = TTY_PARITY;
		else if (receive_data->flags & GB_UART_RECV_FLAG_FRAMING)
			tty_flags = TTY_FRAME;

		/* overrun is special, not associated with a char */
		if (receive_data->flags & GB_UART_RECV_FLAG_OVERRUN)
			tty_insert_flip_char(port, 0, TTY_OVERRUN);
	}
	count = tty_insert_flip_string_fixed_flag(port, receive_data->data,
						  tty_flags, recv_data_size);
	if (count != recv_data_size) {
		dev_err(&gb_tty->gbphy_dev->dev,
			"UART: RX 0x%08x bytes only wrote 0x%08x\n",
			recv_data_size, count);
	}
	if (count)
		tty_flip_buffer_push(port);
	return 0;
}

static int gb_uart_serial_state_handler(struct gb_operation *op)
{
	struct gb_connection *connection = op->connection;
	struct gb_tty *gb_tty = gb_connection_get_data(connection);
	struct gb_message *request = op->request;
	struct gb_uart_serial_state_request *serial_state;

	if (request->payload_size < sizeof(*serial_state)) {
		dev_err(&gb_tty->gbphy_dev->dev,
			"short serial-state event received (%zu < %zu)\n",
			request->payload_size, sizeof(*serial_state));
		return -EINVAL;
	}

	serial_state = request->payload;
	gb_tty->ctrlin = serial_state->control;

	return 0;
}

static int gb_uart_receive_credits_handler(struct gb_operation *op)
{
	struct gb_connection *connection = op->connection;
	struct gb_tty *gb_tty = gb_connection_get_data(connection);
	struct gb_message *request = op->request;
	struct gb_uart_receive_credits_request *credit_request;
	unsigned long flags;
	unsigned int incoming_credits;
	int ret = 0;

	if (request->payload_size < sizeof(*credit_request)) {
		dev_err(&gb_tty->gbphy_dev->dev,
			"short receive_credits event received (%zu < %zu)\n",
			request->payload_size,
			sizeof(*credit_request));
		return -EINVAL;
	}

	credit_request = request->payload;
	incoming_credits = le16_to_cpu(credit_request->count);

	spin_lock_irqsave(&gb_tty->write_lock, flags);
	gb_tty->credits += incoming_credits;
	if (gb_tty->credits >