tty: metag_da: Add metag DA TTY driver

Add a TTY driver for communicating over a Meta DA (Debug Adapter)
channel using the bios channel SWITCH operation.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 694 insertions, 0 deletions

diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 29dfc24f2dbb..978db344bda0 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -406,4 +406,17 @@ config GOLDFISH_TTY
         help
           Console and system TTY driver for the Goldfish virtual platform.
 
+config DA_TTY
+        bool "DA TTY"
+        depends on METAG_DA
+        select SERIAL_NONSTANDARD
+        help
+          This enables a TTY on a Dash channel.
+
+config DA_CONSOLE
+        bool "DA Console"
+        depends on DA_TTY
+        help
+          This enables a console on a Dash channel.
+
 endif # TTY
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index 35649d35abf0..6b78399bc7c9 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -28,5 +28,6 @@ obj-$(CONFIG_SYNCLINKMP)	+= synclinkmp.o
 obj-$(CONFIG_SYNCLINK)          += synclink.o
 obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o
 obj-$(CONFIG_GOLDFISH_TTY)      += goldfish.o
+obj-$(CONFIG_DA_TTY)            += metag_da.o
 
 obj-y += ipwireless/
diff --git a/drivers/tty/metag_da.c b/drivers/tty/metag_da.c
new file mode 100644
index 000000000000..fc2a36bddd3f
--- /dev/null
+++ b/drivers/tty/metag_da.c
@@ -0,0 +1,680 @@
+/*
+ *  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/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;
+
+#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(struct tty_struct *tty)
+{
+        unsigned int channel = tty->index;
+        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 kref to the next channel tty to poll.
+ * Returns:     The TTY of the next channel to poll, or NULL if no TTY needs
+ *              polling. Release with tty_kref_put().
+ */
+static struct tty_struct *find_channel_to_poll(void)
+{
+        static int last_polled_channel;
+        int last = last_polled_channel;
+        int chan;
+        struct tty_struct *tty = NULL;
+
+        for (chan = last + 1; ; ++chan) {
+                if (chan >= NUM_TTY_CHANNELS)
+                        chan = 0;
+
+                tty = tty_port_tty_get(&dashtty_ports[chan].port);
+                if (tty) {
+                        last_polled_channel = chan;
+                        return tty;
+                }
+
+                if (chan == last)
+                        break;
+        }
+        return tty;
+}
+
+/**
+ * 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
+ * channels to write out any buffered data. If any of the channels stall due to
+ * the remote buffer being full, a hold off happens to allow the debugger to
+ * drain the buffer.
+ */
+static int put_data(void *arg)
+{
+        unsigned int chan, stall;
+
+        __set_current_state(TASK_RUNNING);
+        while (!kthread_should_stop()) {
+                /*
+                 * For each channel see if there's anything to transmit in the
+                 * port's xmit_buf.
+                 */
+                stall = 0;
+                for (chan = 0; chan < NUM_TTY_CHANNELS; ++chan)
+                        stall += put_channel_data(chan);
+
+                /*
+                 * If some of the buffers are full, hold off for a short while
+                 * to allow them to empty.
+                 */
+                if (stall)
+                        msleep(25);
+
+                wait_event_interruptible(dashtty_waitqueue,
+                                         atomic_read(&dashtty_xmit_cnt));
+        }
+
+        return 0;
+}
+
+/*
+ *      This gets called every DA_TTY_POLL and polls the channels for data
+ */
+static void dashtty_timer(unsigned long ignored)
+{
+        struct tty_struct *tty;
+
+        /* If there are no ports open do nothing and don't poll again. */
+        if (!atomic_read(&num_channels_need_poll))
+                return;
+
+        tty = find_channel_to_poll();
+
+        /* Did we find a channel to poll? */
+        if (tty) {
+                fetch_data(tty);
+                tty_kref_put(tty);
+        }
+
+        mod_timer_pinned(&poll_timer, jiffies + DA_TTY_POLL);
+}
+
+static void add_poll_timer(struct timer_list *poll_timer)
+{
+        setup_timer(poll_timer, dashtty_timer, 0);
+        poll_timer->expires = jiffies + DA_TTY_POLL;
+
+        /*
+         * Always attach the timer to the boot CPU. The DA channels are per-CPU
+         * so all polling should be from a single CPU.
+         */
+        add_timer_on(poll_timer, 0);
+}
+
+static int dashtty_port_activate(struct tty_port *port, struct tty_struct *tty)
+{
+        struct dashtty_port *dport = container_of(port, struct dashtty_port,
+                                                  port);
+        void *rx_buf;
+
+        /* Allocate the buffer we use for writing data */
+        if (tty_port_alloc_xmit_buf(port) < 0)
+                goto err;
+
+        /* Allocate the buffer we use for reading data */
+        rx_buf = kzalloc(RX_BUF_SIZE, GFP_KERNEL);
+        if (!rx_buf)
+                goto err_free_xmit;
+
+        spin_lock_bh(&dport->rx_lock);
+        dport->rx_buf = rx_buf;
+        spin_unlock_bh(&dport->rx_lock);
+
+        /*
+         * Don't add the poll timer if we're opening a console. This
+         * avoids the overhead of polling the Dash but means it is not
+         * possible to have a login on /dev/console.
+         *
+         */
+        if (dport != &dashtty_ports[CONSOLE_CHANNEL])
+                if (atomic_inc_return(&num_channels_need_poll) == 1)
+                        add_poll_timer(&poll_timer);
+
+        return 0;
+err_free_xmit:
+        tty_port_free_xmit_buf(port);
+err:
+        return -ENOMEM;
+}
+
+static void dashtty_port_shutdown(struct tty_port *port)
+{
+        struct dashtty_port *dport = container_of(port, struct dashtty_port,
+                                                  port);
+        void *rx_buf;
+        unsigned int count;
+
+        /* stop reading */
+        if (dport != &dashtty_ports[CONSOLE_CHANNEL])
+                if (atomic_dec_and_test(&num_channels_need_poll))
+                        del_timer_sync(&poll_timer);
+
+        mutex_lock(&dport->xmit_lock);
+        count = dport->xmit_cnt;
+        mutex_unlock(&dport->xmit_lock);
+        if (count) {
+                /*
+                 * There's still data to write out, so wake and wait for the
+                 * writer thread to drain the buffer.
+                 */
+                del_timer(&put_timer);
+                wake_up_interruptible(&dashtty_waitqueue);
+                wait_for_completion(&dport->xmit_empty);
+        }
+
+        /* Null the read buffer (timer could still be running!) */
+        spin_lock_bh(&dport->rx_lock);
+        rx_buf = dport->rx_buf;
+        dport->rx_buf = NULL;
+        spin_unlock_bh(&dport->rx_lock);
+        /* Free the read buffer */
+        kfree(rx_buf);
+
+        /* Free the write buffer */
+        tty_port_free_xmit_buf(port);
+}
+
+static const struct tty_port_operations dashtty_port_ops = {
+        .activate       = dashtty_port_activate,
+        .shutdown       = dashtty_port_shutdown,
+};
+
+static int dashtty_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+        return tty_port_install(&dashtty_ports[tty->index].port, driver, tty);
+}
+
+static int dashtty_open(struct tty_struct *tty, struct file *filp)
+{
+        return tty_port_open(tty->port, tty, filp);
+}
+
+static void dashtty_close(struct tty_struct *tty, struct file *filp)
+{
+        return tty_port_close(tty->port, tty, filp);
+}
+
+static void dashtty_hangup(struct tty_struct *tty)
+{
+        int channel;
+        struct dashtty_port *dport;
+
+        channel = tty->index;
+        dport = &dashtty_ports[channel];
+
+        /* drop any data in the xmit buffer */
+        mutex_lock(&dport->xmit_lock);
+        if (dport->xmit_cnt) {
+                atomic_sub(dport->xmit_cnt, &dashtty_xmit_cnt);
+                dport->xmit_cnt = 0;
+                dport->xmit_head = 0;
+                dport->xmit_tail = 0;
+                complete(&dport->xmit_empty);
+        }
+        mutex_unlock(&dport->xmit_lock);
+
+        tty_port_hangup(tty->port);
+}
+
+/**
+ * dashtty_put_timer() - Delayed wake up of kernel thread.
+ * @ignored:    unused
+ *
+ * This timer function wakes up the kernel thread if any data exists in the
+ * buffers. It is used to delay the expensive writeout until the writer has
+ * stopped writing.
+ */
+static void dashtty_put_timer(unsigned long ignored)
+{
+        if (atomic_read(&dashtty_xmit_cnt))
+                wake_up_interruptible(&dashtty_waitqueue);
+}
+
+static int dashtty_write(struct tty_struct *tty, const unsigned char *buf,
+                         int total)
+{
+        int channel, count, block;
+        struct dashtty_port *dport;
+
+        /* Determine the channel */
+        channel = tty->index;
+        dport = &dashtty_ports[channel];
+
+        /*
+         * Write to output buffer.
+         *
+         * The reason that we asynchronously write the buffer is because if we
+         * were to write the buffer synchronously then because DA channels are
+         * per-CPU the buffer would be written to the channel of whatever CPU
+         * we're running on.
+         *
+         * What we actually want to happen is have all input and output done on
+         * one CPU.
+         */
+        mutex_lock(&dport->xmit_lock);
+        /* work out how many bytes we can write to the xmit buffer */
+        total = min(total, (int)(SERIAL_XMIT_SIZE - dport->xmit_cnt));
+        atomic_add(total, &dashtty_xmit_cnt);
+        dport->xmit_cnt += total;
+        /* write the actual bytes (may need splitting if it wraps) */
+        for (count = total; count; count -= block) {
+                block = min(count, (int)(SERIAL_XMIT_SIZE - dport->xmit_head));
+                memcpy(dport->port.xmit_buf + dport->xmit_head, buf, block);
+                dport->xmit_head += block;
+                if (dport->xmit_head >= SERIAL_XMIT_SIZE)
+                        dport->xmit_head -= SERIAL_XMIT_SIZE;
+                buf += block;
+        }
+        count = dport->xmit_cnt;
+        /* xmit buffer no longer empty? */
+        if (count)
+                INIT_COMPLETION(dport->xmit_empty);
+        mutex_unlock(&dport->xmit_lock);
+
+        if (total) {
+                /*
+                 * If the buffer is full, wake up the kthread, otherwise allow
+                 * some more time for the buffer to fill up a bit before waking
+                 * it.
+                 */
+                if (count == SERIAL_XMIT_SIZE) {
+                        del_timer(&put_timer);
+                        wake_up_interruptible(&dashtty_waitqueue);
+                } else {
+                        mod_timer(&put_timer, jiffies + DA_TTY_PUT_DELAY);
+                }
+        }
+        return total;
+}
+
+static int dashtty_write_room(struct tty_struct *tty)
+{
+        struct dashtty_port *dport;
+        int channel;
+        int room;
+
+        channel = tty->index;
+        dport = &dashtty_ports[channel];
+
+        /* report the space in the xmit buffer */
+        mutex_lock(&dport->xmit_lock);
+        room = SERIAL_XMIT_SIZE - dport->xmit_cnt;
+        mutex_unlock(&dport->xmit_lock);
+
+        return room;
+}
+
+static int dashtty_chars_in_buffer(struct tty_struct *tty)
+{
+        struct dashtty_port *dport;
+        int channel;
+        int chars;
+
+        channel = tty->index;
+        dport = &dashtty_ports[channel];
+
+        /* report the number of bytes in the xmit buffer */
+        mutex_lock(&dport->xmit_lock);
+        chars = dport->xmit_cnt;
+        mutex_unlock(&dport->xmit_lock);
+
+        return chars;
+}
+
+static const struct tty_operations dashtty_ops = {
+        .install                = dashtty_install,
+        .open                   = dashtty_open,
+        .close                  = dashtty_close,
+        .hangup                 = dashtty_hangup,
+        .write                  = dashtty_write,
+        .write_room             = dashtty_write_room,
+        .chars_in_buffer        = dashtty_chars_in_buffer,
+};
+
+static int __init dashtty_init(void)
+{
+        int ret;
+        int nport;
+        struct dashtty_port *dport;
+
+        if (!metag_da_enabled())
+                return -ENODEV;
+
+        channel_driver = tty_alloc_driver(NUM_TTY_CHANNELS,
+                                          TTY_DRIVER_REAL_RAW);
+        if (IS_ERR(channel_driver))
+                return PTR_ERR(channel_driver);
+
+        channel_driver->driver_name = "metag_da";
+        channel_driver->name = "ttyDA";
+        channel_driver->major = DA_TTY_MAJOR;
+        channel_driver->minor_start = 0;
+        channel_driver->type = TTY_DRIVER_TYPE_SERIAL;
+        channel_driver->subtype = SERIAL_TYPE_NORMAL;
+        channel_driver->init_termios = tty_std_termios;
+        channel_driver->init_termios.c_cflag |= CLOCAL;
+
+        tty_set_operations(channel_driver, &dashtty_ops);
+        for (nport = 0; nport < NUM_TTY_CHANNELS; nport++) {
+                dport = &dashtty_ports[nport];
+                tty_port_init(&dport->port);
+                dport->port.ops = &dashtty_port_ops;
+                spin_lock_init(&dport->rx_lock);
+                mutex_init(&dport->xmit_lock);
+                /* the xmit buffer starts empty, i.e. completely written */
+                init_completion(&dport->xmit_empty);
+                complete(&dport->xmit_empty);
+        }
+
+        setup_timer(&put_timer, dashtty_put_timer, 0);
+
+        init_waitqueue_head(&dashtty_waitqueue);
+        dashtty_thread = kthread_create(put_data, NULL, "ttyDA");
+        if (IS_ERR(dashtty_thread)) {
+                pr_err("Couldn't create dashtty thread\n");
+                ret = PTR_ERR(dashtty_thread);
+                goto err_destroy_ports;
+        }
+        /*
+         * Bind the writer thread to the boot CPU so it can't migrate.
+         * DA channels are per-CPU and we want all channel I/O to be on a single
+         * predictable CPU.
+         */
+        kthread_bind(dashtty_thread, 0);
+        wake_up_process(dashtty_thread);
+
+        ret = tty_register_driver(channel_driver);
+
+        if (ret < 0) {
+                pr_err("Couldn't install dashtty driver: err %d\n",
+                       ret);
+                goto err_stop_kthread;
+        }
+
+        return 0;
+
+err_stop_kthread:
+        kthread_stop(dashtty_thread);
+err_destroy_ports:
+        for (nport = 0; nport < NUM_TTY_CHANNELS; nport++) {
+                dport = &dashtty_ports[nport];
+                tty_port_destroy(&dport->port);
+        }
+        put_tty_driver(channel_driver);
+        return ret;
+}
+
+static void dashtty_exit(void)
+{
+        int nport;
+        struct dashtty_port *dport;
+
+        del_timer_sync(&put_timer);
+        kthread_stop(dashtty_thread);
+        del_timer_sync(&poll_timer);
+        tty_unregister_driver(channel_driver);
+        for (nport = 0; nport < NUM_TTY_CHANNELS; nport++) {
+                dport = &dashtty_ports[nport];
+                tty_port_destroy(&dport->port);
+        }
+        put_tty_driver(channel_driver);
+}
+
+module_init(dashtty_init);
+module_exit(dashtty_exit);
+
+#ifdef CONFIG_DA_CONSOLE
+
+static void dash_console_write(struct console *co, const char *s,
+                               unsigned int count)
+{
+        int actually_written;
+
+        chancall(WRBUF, CONSOLE_CHANNEL, count, (void *)s, &actually_written);
+}
+
+static struct tty_driver *dash_console_device(struct console *c, int *index)
+{
+        *index = c->index;
+        return channel_driver;
+}
+
+struct console dash_console = {
+        .name = "ttyDA",
+        .write = dash_console_write,
+        .device = dash_console_device,
+        .flags = CON_PRINTBUFFER,
+        .index = 1,
+};
+
+#endif