path: root/drivers/tty/metag_da.c

/*
 *  dashtty.c - tty driver for Dash channels interface.
 *
 *  Copyright (C) 2007,2008,2012 Imagination Technologies
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file COPYING in the main directory of this archive
 * for more details.
 *
 */

#include <linux/atomic.h>
#include <linux/completion.h>
#include <linux/console.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/moduleparam.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/serial.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/uaccess.h>

#include <asm/da.h>

/* Channel error codes */
#define CONAOK	0
#define CONERR	1
#define CONBAD	2
#define CONPRM	3
#define CONADR	4
#define CONCNT	5
#define CONCBF	6
#define CONCBE	7
#define CONBSY	8

/* Default channel for the console */
#define CONSOLE_CHANNEL      1

#define NUM_TTY_CHANNELS     6

/* Auto allocate */
#define DA_TTY_MAJOR        0

/* A speedy poll rate helps the userland debug process connection response.
 * But, if you set it too high then no other userland processes get much
 * of a look in.
 */
#define DA_TTY_POLL (HZ / 50)

/*
 * A short put delay improves latency but has a high throughput overhead
 */
#define DA_TTY_PUT_DELAY (HZ / 100)

static atomic_t num_channels_need_poll = ATOMIC_INIT(0);

static struct timer_list poll_timer;

static struct tty_driver *channel_driver;

static struct timer_list put_timer;
static struct task_struct *dashtty_thread;

/*
 * The console_poll parameter determines whether the console channel should be
 * polled for input.
 * By default the console channel isn't polled at all, in order to avoid the
 * overhead, but that means it isn't possible to have a login on /dev/console.
 */
static bool console_poll;
module_param(console_poll, bool, S_IRUGO);

#define RX_BUF_SIZE 1024

enum {
	INCHR = 1,
	OUTCHR,
	RDBUF,
	WRBUF,
	RDSTAT
};

/**
 * struct dashtty_port - Wrapper struct for dashtty tty_port.
 * @port:		TTY port data
 * @rx_lock:		Lock for rx_buf.
 *			This protects between the poll timer and user context.
 *			It's also held during read SWITCH operations.
 * @rx_buf:		Read buffer
 * @xmit_lock:		Lock for xmit_*, and port.xmit_buf.
 *			This protects between user context and kernel thread.
 *			It's also held during write SWITCH operations.
 * @xmit_cnt:		Size of xmit buffer contents
 * @xmit_head:		Head of xmit buffer where data is written
 * @xmit_tail:		Tail of xmit buffer where data is read
 * @xmit_empty:		Completion for xmit buffer being empty
 */
struct dashtty_port {
	struct tty_port		 port;
	spinlock_t		 rx_lock;
	void			*rx_buf;
	struct mutex		 xmit_lock;
	unsigned int		 xmit_cnt;
	unsigned int		 xmit_head;
	unsigned int		 xmit_tail;
	struct completion	 xmit_empty;
};

static struct dashtty_port dashtty_ports[NUM_TTY_CHANNELS];

static atomic_t dashtty_xmit_cnt = ATOMIC_INIT(0);
static wait_queue_head_t dashtty_waitqueue;

/*
 * Low-level DA channel access routines
 */
static int chancall(int in_bios_function, int in_channel,
		    int in_arg2, void *in_arg3,
		    void *in_arg4)
{
	register int   bios_function asm("D1Ar1") = in_bios_function;
	register int   channel       asm("D0Ar2") = in_channel;
	register int   arg2          asm("D1Ar3") = in_arg2;
	register void *arg3          asm("D0Ar4") = in_arg3;
	register void *arg4          asm("D1Ar5") = in_arg4;
	register int   bios_call     asm("D0Ar6") = 3;
	register int   result        asm("D0Re0");

	asm volatile (
		"MSETL	[A0StP++], %6,%4,%2\n\t"
		"ADD	A0StP, A0StP, #8\n\t"
		"SWITCH	#0x0C30208\n\t"
		"GETD	%0, [A0StP+#-8]\n\t"
		"SUB	A0StP, A0StP, #(4*6)+8\n\t"
		: "=d" (result)   /* outs */
		: "d" (bios_function),
		  "d" (channel),
		  "d" (arg2),
		  "d" (arg3),
		  "d" (arg4),
		  "d" (bios_call) /* ins */
		: "memory");

	return result;
}

/*
 * Attempts to fetch count bytes from channel and returns actual count.
 */
static int fetch_data(unsigned int channel)
{
	struct dashtty_port *dport = &dashtty_ports[channel];
	int received = 0;

	spin_lock_bh(&dport->rx_lock);
	/* check the port isn't being shut down */
	if (!dport->rx_buf)
		goto unlock;
	if (chancall(RDBUF, channel, RX_BUF_SIZE,
		     (void *)dport->rx_buf, &received) == CONAOK) {
		if (received) {
			int space;
			unsigned char *cbuf;

			space = tty_prepare_flip_string(&dport->port, &cbuf,
							received);

			if (space <= 0)
				goto unlock;

			memcpy(cbuf, dport->rx_buf, space);
			tty_flip_buffer_push(&dport->port);
		}
	}
unlock:
	spin_unlock_bh(&dport->rx_lock);

	return received;
}

/**
 * find_channel_to_poll() - Returns number of the next channel to poll.
 * Returns:	The number of the next channel to poll, or -1 if none need
 *		polling.
 */
static int find_channel_to_poll(void)
{
	static int last_polled_channel;
	int last = last_polled_channel;
	int chan;
	struct dashtty_port *dport;

	for (chan = last + 1; ; ++chan) {
		if (chan >= NUM_TTY_CHANNELS)
			chan = 0;

		dport = &dashtty_ports[chan];
		if (dport->rx_buf) {
			last_polled_channel = chan;
			return chan;
		}

		if (chan == last)
			break;
	}
	return -1;
}

/**
 * put_channel_data() - Write out a block of channel data.
 * @chan:	DA channel number.
 *
 * Write a single block of data out to the debug adapter. If the circular buffer
 * is wrapped then only the first block is written.
 *
 * Returns:	1 if the remote buffer was too full to accept data.
 *		0 otherwise.
 */
static int put_channel_data(unsigned int chan)
{
	struct dashtty_port *dport;
	struct tty_struct *tty;
	int number_written;
	unsigned int count = 0;

	dport = &dashtty_ports[chan];
	mutex_lock(&dport->xmit_lock);
	if (dport->xmit_cnt) {
		count = min((unsigned int)(SERIAL_XMIT_SIZE - dport->xmit_tail),
			    dport->xmit_cnt);
		chancall(WRBUF, chan, count,
			 dport->port.xmit_buf + dport->xmit_tail,
			 &number_written);
		dport->xmit_cnt -= number_written;
		if (!dport->xmit_cnt) {
			/* reset pointers to avoid wraps */
			dport->xmit_head = 0;
			dport->xmit_tail = 0;
			complete(&dport->xmit_empty);
		} else {
			dport->xmit_tail += number_written;
			if (dport->xmit_tail >= SERIAL_XMIT_SIZE)
				dport->xmit_tail -= SERIAL_XMIT_SIZE;
		}
		atomic_sub(number_written, &dashtty_xmit_cnt);
	}
	mutex_unlock(&dport->xmit_lock);

	/* if we've made more data available, wake up tty */
	if (count && number_written) {
		tty = tty_port_tty_get(&dport->port);
		if (tty) {
			tty_wakeup(tty);
			tty_kref_put(tty);
		}
	}

	/* did the write fail? */
	return count && !number_written;
}

/**
 * put_data() - Kernel thread to write out blocks of channel data to DA.
 * @arg:	Unused.
 *
 * This kernel thread runs while @dashtty_xmit_cnt != 0, and loops over the