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SubjectRe: [PATCH v3 43/44] tty/metag_da: Add metag DA TTY driver
Hi,

On 14/01/13 10:54, James Hogan wrote:
> Here's a new version addressing Jiri's feedback.
>
> 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: Alan Cox <alan@lxorguk.ukuu.org.uk>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jiri Slaby <jslaby@suse.cz>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
> Cc: Cesar Eduardo Barros <cesarb@cesarb.net>
> Cc: Joe Perches <joe@perches.com>
> Cc: "David S. Miller" <davem@davemloft.net>

If this looks okay, I'd appreciate if somebody could Ack it.

I have some further patches ready to simplify the code around
tty_prepare_flip_string and tty_flip_buffer_push to avoid taking a tty
kref, after Jiri's changes in that area in linux-next. I guess these can
be applied once both sets of changes are merged.

Thanks
James

> ---
> MAINTAINERS | 1 +
> arch/metag/Kconfig | 4 +-
> arch/metag/configs/meta1_defconfig | 2 +
> arch/metag/configs/meta2_defconfig | 2 +
> arch/metag/configs/meta2_smp_defconfig | 2 +
> arch/metag/kernel/setup.c | 12 +
> drivers/tty/Kconfig | 13 +
> drivers/tty/Makefile | 1 +
> drivers/tty/metag_da.c | 679 ++++++++++++++++++++++++++++++++
> 9 files changed, 715 insertions(+), 1 deletions(-)
> create mode 100644 drivers/tty/metag_da.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index dbc2bd6..63ccab6 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5002,6 +5002,7 @@ S: Supported
> F: arch/metag/
> F: Documentation/metag/
> F: Documentation/devicetree/bindings/metag/
> +F: drivers/tty/metag_da.c
>
> MICROBLAZE ARCHITECTURE
> M: Michal Simek <monstr@monstr.eu>
> diff --git a/arch/metag/Kconfig b/arch/metag/Kconfig
> index 9bd0bc1..f4ef3bb 100644
> --- a/arch/metag/Kconfig
> +++ b/arch/metag/Kconfig
> @@ -221,7 +221,9 @@ config METAG_DA
> of the DA will be detected automatically at boot, so it is safe to say
> Y to this option even when booting without a DA.
>
> - This enables support for services provided by DA JTAG debug adapters.
> + This enables support for services provided by DA JTAG debug adapters,
> + such as:
> + - communication over DA channels (such as the console driver).
>
> menu "Boot options"
>
> diff --git a/arch/metag/configs/meta1_defconfig b/arch/metag/configs/meta1_defconfig
> index 0773425..ad663ca 100644
> --- a/arch/metag/configs/meta1_defconfig
> +++ b/arch/metag/configs/meta1_defconfig
> @@ -28,6 +28,8 @@ CONFIG_BLK_DEV_RAM_SIZE=16384
> # CONFIG_SERIO is not set
> # CONFIG_VT is not set
> # CONFIG_LEGACY_PTYS is not set
> +CONFIG_DA_TTY=y
> +CONFIG_DA_CONSOLE=y
> # CONFIG_DEVKMEM is not set
> # CONFIG_HW_RANDOM is not set
> # CONFIG_HWMON is not set
> diff --git a/arch/metag/configs/meta2_defconfig b/arch/metag/configs/meta2_defconfig
> index 001f9bf..47922e93 100644
> --- a/arch/metag/configs/meta2_defconfig
> +++ b/arch/metag/configs/meta2_defconfig
> @@ -29,6 +29,8 @@ CONFIG_BLK_DEV_RAM_SIZE=16384
> # CONFIG_SERIO is not set
> # CONFIG_VT is not set
> # CONFIG_LEGACY_PTYS is not set
> +CONFIG_DA_TTY=y
> +CONFIG_DA_CONSOLE=y
> # CONFIG_DEVKMEM is not set
> # CONFIG_HW_RANDOM is not set
> # CONFIG_HWMON is not set
> diff --git a/arch/metag/configs/meta2_smp_defconfig b/arch/metag/configs/meta2_smp_defconfig
> index d6f7e46..f508250 100644
> --- a/arch/metag/configs/meta2_smp_defconfig
> +++ b/arch/metag/configs/meta2_smp_defconfig
> @@ -30,6 +30,8 @@ CONFIG_BLK_DEV_RAM_SIZE=16384
> # CONFIG_SERIO is not set
> # CONFIG_VT is not set
> # CONFIG_LEGACY_PTYS is not set
> +CONFIG_DA_TTY=y
> +CONFIG_DA_CONSOLE=y
> # CONFIG_DEVKMEM is not set
> # CONFIG_HW_RANDOM is not set
> # CONFIG_HWMON is not set
> diff --git a/arch/metag/kernel/setup.c b/arch/metag/kernel/setup.c
> index 1410db0..0d46334 100644
> --- a/arch/metag/kernel/setup.c
> +++ b/arch/metag/kernel/setup.c
> @@ -61,6 +61,11 @@ extern char _heap_start[];
> extern u32 __dtb_start[];
> #endif
>
> +#ifdef CONFIG_DA_CONSOLE
> +/* Our early channel based console driver */
> +extern struct console dash_console;
> +#endif
> +
> struct machine_desc *machine_desc __initdata;
>
> /*
> @@ -182,6 +187,13 @@ void __init setup_arch(char **cmdline_p)
> metag_cache_probe();
>
> metag_da_probe();
> +#ifdef CONFIG_DA_CONSOLE
> + if (metag_da_enabled()) {
> + /* An early channel based console driver */
> + register_console(&dash_console);
> + add_preferred_console("ttyDA", 1, NULL);
> + }
> +#endif
>
> /* try interpreting the argument as a device tree */
> machine_desc = setup_machine_fdt(original_cmd_line);
> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
> index 0ecf22b..5eef53d 100644
> --- a/drivers/tty/Kconfig
> +++ b/drivers/tty/Kconfig
> @@ -388,3 +388,16 @@ config PPC_EARLY_DEBUG_EHV_BC_HANDLE
> If the number you specify is not a valid byte channel handle, then
> there simply will be no early console output. This is true also
> if you don't boot under a hypervisor at all.
> +
> +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.
> diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
> index 2953059..dbd7745 100644
> --- a/drivers/tty/Makefile
> +++ b/drivers/tty/Makefile
> @@ -27,5 +27,6 @@ obj-$(CONFIG_SYNCLINK_GT) += synclink_gt.o
> obj-$(CONFIG_SYNCLINKMP) += synclinkmp.o
> obj-$(CONFIG_SYNCLINK) += synclink.o
> obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.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..6a0b2e6
> --- /dev/null
> +++ b/drivers/tty/metag_da.c
> @@ -0,0 +1,679 @@
> +/*
> + * 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(tty, &cbuf, received);
> +
> + if (space <= 0)
> + goto unlock;
> +
> + memcpy(cbuf, dport->rx_buf, space);
> + tty_flip_buffer_push(tty);
> + }
> + }
> +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
>

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