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|
/*
* 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;
}
/**
|