[PATCH 1/2] tty: metag_da: Add metag DA TTY driver

James Hogan
2013-02-06T14:46:05Z

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>
---
The only changes compared to v4 of arch/metag patchset are trivial:
* removal of arch/metag changes
* squashed in tty_prepare_flip_string and tty_flip_buffer_push fix

drivers/tty/Kconfig | 13 +
drivers/tty/Makefile | 1 +
drivers/tty/metag_da.c | 680 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 694 insertions(+), 0 deletions(-)
create mode 100644 drivers/tty/metag_da.c

diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 29dfc24..978db34 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 35649d3..6b78399 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 0000000..fc2a36b
--- /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
--
1.7.7.6