path: root/drivers/tty/serial/mrst_max3110.c

/*
 *  mrst_max3110.c - spi uart protocol driver for Maxim 3110
 *
 * Copyright (c) 2008-2010, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 */

/*
 * Note:
 * 1. From Max3110 spec, the Rx FIFO has 8 words, while the Tx FIFO only has
 *    1 word. If SPI master controller doesn't support sclk frequency change,
 *    then the char need be sent out one by one with some delay
 *
 * 2. Currently only RX available interrupt is used, no need for waiting TXE
 *    interrupt for a low speed UART device
 */

#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial_reg.h>

#include <linux/kthread.h>
#include <linux/spi/spi.h>

#include "mrst_max3110.h"

#define PR_FMT	"mrst_max3110: "

#define UART_TX_NEEDED 1
#define CON_TX_NEEDED  2
#define BIT_IRQ_PENDING    3

struct uart_max3110 {
	struct uart_port port;
	struct spi_device *spi;
	char name[SPI_NAME_SIZE];

	wait_queue_head_t wq;
	struct task_struct *main_thread;
	struct task_struct *read_thread;
	struct mutex thread_mutex;

	u32 baud;
	u16 cur_conf;
	u8 clock;
	u8 parity, word_7bits;
	u16 irq;

	unsigned long uart_flags;

	/* console related */
	struct circ_buf con_xmit;
};

/* global data structure, may need be removed */
static struct uart_max3110 *pmax;

static void receive_chars(struct uart_max3110 *max,
				unsigned char *str, int len);
static int max3110_read_multi(struct uart_max3110 *max, u8 *buf);
static void max3110_con_receive(struct uart_max3110 *max);

static int max3110_write_then_read(struct uart_max3110 *max,
		const void *txbuf, void *rxbuf, unsigned len, int always_fast)
{
	struct spi_device *spi = max->spi;
	struct spi_message	message;
	struct spi_transfer	x;
	int ret;

	spi_message_init(&message);
	memset(&x, 0, sizeof x);
	x.len = len;
	x.tx_buf = txbuf;
	x.rx_buf = rxbuf;
	spi_message_add_tail(&x, &message);

	if (always_fast)
		x.speed_hz = spi->max_speed_hz;
	else if (max->baud)
		x.speed_hz = max->baud;

	/* Do the i/o */
	ret = spi_sync(spi, &message);
	return ret;
}

/* Write a 16b word to the device */
static int max3110_out(struct uart_max3110 *max, const u16 out)
{
	void *buf;
	u16 *obuf, *ibuf;
	u8  ch;
	int ret;

	buf = kzalloc(8, GFP_KERNEL | GFP_DMA);
	if (!buf)
		return -ENOMEM;

	obuf = buf;
	ibuf = buf + 4;
	*obuf = out;
	ret = max3110_write_then_read(max, obuf, ibuf, 2, 1);
	if (ret) {
		pr_warning(PR_FMT "%s(): get err msg %d when sending 0x%x\n",
				__func__, ret, out);
		goto exit;
	}

	/* If some valid data is read back */
	if (*ibuf & MAX3110_READ_DATA_AVAILABLE) {
		ch = *ibuf & 0xff;
		receive_chars(max, &ch, 1);
	}

exit:
	kfree(buf);
	return ret;
}

/*
 * This is usually used to read data from SPIC RX FIFO, which doesn't
 * need any delay like flushing character out.
 *
 * Return how many valide bytes are read back
 */
static int max3110_read_multi(struct uart_max3110 *max, u8 *rxbuf)
{
	void *buf;
	u16 *obuf, *ibuf;
	u8 *pbuf, valid_str[M3110_RX_FIFO_DEPTH];
	int i, j, blen;

	blen = M3110_RX_FIFO_DEPTH * sizeof(u16);
	buf = kzalloc(blen * 2, GFP_KERNEL | GFP_DMA);
	if (!buf) {
		pr_warning(PR_FMT "%s(): fail to alloc dma buffer\n", __func__);
		return 0;
	}

	/* tx/rx always have the same length */
	obuf = buf;
	ibuf = buf + blen;

	if (max3110_write_then_read(max, obuf, ibuf, blen, 1)) {
		kfree(buf);
		return 0;
	}

	/* If caller doesn't provide a buffer, then handle received char */
	pbuf = rxbuf ? rxbuf : valid_str;

	for (i = 0, j = 0; i < M3110_RX_FIFO_DEPTH; i++) {
		if (ibuf[i] & MAX3110_READ_DATA_AVAILABLE)
			pbuf[j++] = ibuf[i] & 0xff;
	}

	if (j && (pbuf == valid_str))
		receive_chars(max, valid_str,