This reverts commit 0c57dfcc6c1d037243c2f8fbf62eab3633326ec0.

The functionality was supoosed to be used by a later patch in the
series that never landed [1]. Drop it.

NOTE: part of functionality was already reverted by commit
39d0be87438a ("serial: kgdb_nmi: Remove unused knock code"). Also note
that this revert is not a clean revert given code changes that have
happened in the meantime.

It's obvious that nobody is using this code since the two exposed
functions (kgdb_register_nmi_console() and
kgdb_unregister_nmi_console()) are both no-ops if
"arch_kgdb_ops.enable_nmi" is not defined. No architectures define it.

[1] 
https://lore.kernel.org/lkml/1348522080-32629-9-git-send-email-anton.voront...@linaro.org/

Signed-off-by: Douglas Anderson <diand...@chromium.org>
---

 drivers/tty/serial/Kconfig    |  19 ---
 drivers/tty/serial/Makefile   |   1 -
 drivers/tty/serial/kgdb_nmi.c | 280 ----------------------------------
 drivers/tty/serial/kgdboc.c   |   8 -
 include/linux/kgdb.h          |   8 -
 5 files changed, 316 deletions(-)
 delete mode 100644 drivers/tty/serial/kgdb_nmi.c

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 976dae3bb1bb..f21cad6aaa47 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -179,25 +179,6 @@ config SERIAL_ATMEL_TTYAT
 
          Say Y if you have an external 8250/16C550 UART.  If unsure, say N.
 
-config SERIAL_KGDB_NMI
-       bool "Serial console over KGDB NMI debugger port"
-       depends on KGDB_SERIAL_CONSOLE
-       help
-         This special driver allows you to temporary use NMI debugger port
-         as a normal console (assuming that the port is attached to KGDB).
-
-         Unlike KDB's disable_nmi command, with this driver you are always
-         able to go back to the debugger using KGDB escape sequence ($3#33).
-         This is because this console driver processes the input in NMI
-         context, and thus is able to intercept the magic sequence.
-
-         Note that since the console interprets input and uses polling
-         communication methods, for things like PPP you still must fully
-         detach debugger port from the KGDB NMI (i.e. disable_nmi), and
-         use raw console.
-
-         If unsure, say N.
-
 config SERIAL_MESON
        tristate "Meson serial port support"
        depends on ARCH_MESON || COMPILE_TEST
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 6ff74f0a9530..3019260d9120 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -96,6 +96,5 @@ obj-$(CONFIG_SERIAL_ZS)                       += zs.o
 # GPIOLIB helpers for modem control lines
 obj-$(CONFIG_SERIAL_MCTRL_GPIO)        += serial_mctrl_gpio.o
 
-obj-$(CONFIG_SERIAL_KGDB_NMI) += kgdb_nmi.o
 obj-$(CONFIG_KGDB_SERIAL_CONSOLE) += kgdboc.o
 obj-$(CONFIG_SERIAL_NUVOTON_MA35D1) += ma35d1_serial.o
diff --git a/drivers/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c
deleted file mode 100644
index 2833708e369f..000000000000
--- a/drivers/tty/serial/kgdb_nmi.c
+++ /dev/null
@@ -1,280 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * KGDB NMI serial console
- *
- * Copyright 2010 Google, Inc.
- *               Arve Hjønnevåg <a...@android.com>
- *               Colin Cross <ccr...@android.com>
- * Copyright 2012 Linaro Ltd.
- *               Anton Vorontsov <anton.voront...@linaro.org>
- */
-
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/compiler.h>
-#include <linux/slab.h>
-#include <linux/errno.h>
-#include <linux/atomic.h>
-#include <linux/console.h>
-#include <linux/tty.h>
-#include <linux/tty_driver.h>
-#include <linux/tty_flip.h>
-#include <linux/serial_core.h>
-#include <linux/interrupt.h>
-#include <linux/hrtimer.h>
-#include <linux/tick.h>
-#include <linux/kfifo.h>
-#include <linux/kgdb.h>
-#include <linux/kdb.h>
-
-static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0);
-
-static int kgdb_nmi_console_setup(struct console *co, char *options)
-{
-       arch_kgdb_ops.enable_nmi(1);
-
-       /* The NMI console uses the dbg_io_ops to issue console messages. To
-        * avoid duplicate messages during kdb sessions we must inform kdb's
-        * I/O utilities that messages sent to the console will automatically
-        * be displayed on the dbg_io.
-        */
-       dbg_io_ops->cons = co;
-
-       return 0;
-}
-
-static void kgdb_nmi_console_write(struct console *co, const char *s, uint c)
-{
-       int i;
-
-       for (i = 0; i < c; i++)
-               dbg_io_ops->write_char(s[i]);
-}
-
-static struct tty_driver *kgdb_nmi_tty_driver;
-
-static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx)
-{
-       *idx = co->index;
-       return kgdb_nmi_tty_driver;
-}
-
-static struct console kgdb_nmi_console = {
-       .name   = "ttyNMI",
-       .setup  = kgdb_nmi_console_setup,
-       .write  = kgdb_nmi_console_write,
-       .device = kgdb_nmi_console_device,
-       .flags  = CON_PRINTBUFFER | CON_ANYTIME,
-       .index  = -1,
-};
-
-/*
- * This is usually the maximum rate on debug ports. We make fifo large enough
- * to make copy-pasting to the terminal usable.
- */
-#define KGDB_NMI_BAUD          115200
-#define KGDB_NMI_FIFO_SIZE     roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ)
-
-struct kgdb_nmi_tty_priv {
-       struct tty_port port;
-       struct timer_list timer;
-       STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;
-};
-
-static struct tty_port *kgdb_nmi_port;
-
-/*
- * The tasklet is cheap, it does not cause wakeups when reschedules itself,
- * instead it waits for the next tick.
- */
-static void kgdb_nmi_tty_receiver(struct timer_list *t)
-{
-       struct kgdb_nmi_tty_priv *priv = from_timer(priv, t, timer);
-       char ch;
-
-       priv->timer.expires = jiffies + (HZ/100);
-       add_timer(&priv->timer);
-
-       if (likely(!atomic_read(&kgdb_nmi_num_readers) ||
-                  !kfifo_len(&priv->fifo)))
-               return;
-
-       while (kfifo_out(&priv->fifo, &ch, 1))
-               tty_insert_flip_char(&priv->port, ch, TTY_NORMAL);
-       tty_flip_buffer_push(&priv->port);
-}
-
-static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty)
-{
-       struct kgdb_nmi_tty_priv *priv =
-           container_of(port, struct kgdb_nmi_tty_priv, port);
-
-       kgdb_nmi_port = port;
-       priv->timer.expires = jiffies + (HZ/100);
-       add_timer(&priv->timer);
-
-       return 0;
-}
-
-static void kgdb_nmi_tty_shutdown(struct tty_port *port)
-{
-       struct kgdb_nmi_tty_priv *priv =
-           container_of(port, struct kgdb_nmi_tty_priv, port);
-
-       del_timer(&priv->timer);
-       kgdb_nmi_port = NULL;
-}
-
-static const struct tty_port_operations kgdb_nmi_tty_port_ops = {
-       .activate       = kgdb_nmi_tty_activate,
-       .shutdown       = kgdb_nmi_tty_shutdown,
-};
-
-static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty)
-{
-       struct kgdb_nmi_tty_priv *priv;
-       int ret;
-
-       priv = kzalloc(sizeof(*priv), GFP_KERNEL);
-       if (!priv)
-               return -ENOMEM;
-
-       INIT_KFIFO(priv->fifo);
-       timer_setup(&priv->timer, kgdb_nmi_tty_receiver, 0);
-       tty_port_init(&priv->port);
-       priv->port.ops = &kgdb_nmi_tty_port_ops;
-       tty->driver_data = priv;
-
-       ret = tty_port_install(&priv->port, drv, tty);
-       if (ret) {
-               pr_err("%s: can't install tty port: %d\n", __func__, ret);
-               goto err;
-       }
-       return 0;
-err:
-       tty_port_destroy(&priv->port);
-       kfree(priv);
-       return ret;
-}
-
-static void kgdb_nmi_tty_cleanup(struct tty_struct *tty)
-{
-       struct kgdb_nmi_tty_priv *priv = tty->driver_data;
-
-       tty->driver_data = NULL;
-       tty_port_destroy(&priv->port);
-       kfree(priv);
-}
-
-static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file)
-{
-       struct kgdb_nmi_tty_priv *priv = tty->driver_data;
-       unsigned int mode = file->f_flags & O_ACCMODE;
-       int ret;
-
-       ret = tty_port_open(&priv->port, tty, file);
-       if (!ret && (mode == O_RDONLY || mode == O_RDWR))
-               atomic_inc(&kgdb_nmi_num_readers);
-
-       return ret;
-}
-
-static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file)
-{
-       struct kgdb_nmi_tty_priv *priv = tty->driver_data;
-       unsigned int mode = file->f_flags & O_ACCMODE;
-
-       if (mode == O_RDONLY || mode == O_RDWR)
-               atomic_dec(&kgdb_nmi_num_readers);
-
-       tty_port_close(&priv->port, tty, file);
-}
-
-static void kgdb_nmi_tty_hangup(struct tty_struct *tty)
-{
-       struct kgdb_nmi_tty_priv *priv = tty->driver_data;
-
-       tty_port_hangup(&priv->port);
-}
-
-static unsigned int kgdb_nmi_tty_write_room(struct tty_struct *tty)
-{
-       /* Actually, we can handle any amount as we use polled writes. */
-       return 2048;
-}
-
-static ssize_t kgdb_nmi_tty_write(struct tty_struct *tty, const u8 *buf,
-                                 size_t c)
-{
-       int i;
-
-       for (i = 0; i < c; i++)
-               dbg_io_ops->write_char(buf[i]);
-       return c;
-}
-
-static const struct tty_operations kgdb_nmi_tty_ops = {
-       .open           = kgdb_nmi_tty_open,
-       .close          = kgdb_nmi_tty_close,
-       .install        = kgdb_nmi_tty_install,
-       .cleanup        = kgdb_nmi_tty_cleanup,
-       .hangup         = kgdb_nmi_tty_hangup,
-       .write_room     = kgdb_nmi_tty_write_room,
-       .write          = kgdb_nmi_tty_write,
-};
-
-int kgdb_register_nmi_console(void)
-{
-       int ret;
-
-       if (!arch_kgdb_ops.enable_nmi)
-               return 0;
-
-       kgdb_nmi_tty_driver = tty_alloc_driver(1, TTY_DRIVER_REAL_RAW);
-       if (IS_ERR(kgdb_nmi_tty_driver)) {
-               pr_err("%s: cannot allocate tty\n", __func__);
-               return PTR_ERR(kgdb_nmi_tty_driver);
-       }
-       kgdb_nmi_tty_driver->driver_name        = "ttyNMI";
-       kgdb_nmi_tty_driver->name               = "ttyNMI";
-       kgdb_nmi_tty_driver->num                = 1;
-       kgdb_nmi_tty_driver->type               = TTY_DRIVER_TYPE_SERIAL;
-       kgdb_nmi_tty_driver->subtype            = SERIAL_TYPE_NORMAL;
-       kgdb_nmi_tty_driver->init_termios       = tty_std_termios;
-       tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios,
-                                    KGDB_NMI_BAUD, KGDB_NMI_BAUD);
-       tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops);
-
-       ret = tty_register_driver(kgdb_nmi_tty_driver);
-       if (ret) {
-               pr_err("%s: can't register tty driver: %d\n", __func__, ret);
-               goto err_drv_reg;
-       }
-
-       register_console(&kgdb_nmi_console);
-
-       return 0;
-err_drv_reg:
-       tty_driver_kref_put(kgdb_nmi_tty_driver);
-       return ret;
-}
-EXPORT_SYMBOL_GPL(kgdb_register_nmi_console);
-
-int kgdb_unregister_nmi_console(void)
-{
-       int ret;
-
-       if (!arch_kgdb_ops.enable_nmi)
-               return 0;
-       arch_kgdb_ops.enable_nmi(0);
-
-       ret = unregister_console(&kgdb_nmi_console);
-       if (ret)
-               return ret;
-
-       tty_unregister_driver(kgdb_nmi_tty_driver);
-       tty_driver_kref_put(kgdb_nmi_tty_driver);
-
-       return 0;
-}
-EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console);
diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 58ea1e1391ce..85f6c5a76e0f 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -186,8 +186,6 @@ static void cleanup_kgdboc(void)
        if (configured != 1)
                return;
 
-       if (kgdb_unregister_nmi_console())
-               return;
        kgdboc_unregister_kbd();
        kgdb_unregister_io_module(&kgdboc_io_ops);
 }
@@ -250,16 +248,10 @@ static int configure_kgdboc(void)
        if (err)
                goto noconfig;
 
-       err = kgdb_register_nmi_console();
-       if (err)
-               goto nmi_con_failed;
-
        configured = 1;
 
        return 0;
 
-nmi_con_failed:
-       kgdb_unregister_io_module(&kgdboc_io_ops);
 noconfig:
        kgdboc_unregister_kbd();
        configured = 0;
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 51ef131e66b7..14739952698b 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -306,14 +306,6 @@ extern const struct kgdb_arch              arch_kgdb_ops;
 
 extern unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs);
 
-#ifdef CONFIG_SERIAL_KGDB_NMI
-extern int kgdb_register_nmi_console(void);
-extern int kgdb_unregister_nmi_console(void);
-#else
-static inline int kgdb_register_nmi_console(void) { return 0; }
-static inline int kgdb_unregister_nmi_console(void) { return 0; }
-#endif
-
 extern int kgdb_register_io_module(struct kgdb_io *local_kgdb_io_ops);
 extern void kgdb_unregister_io_module(struct kgdb_io *local_kgdb_io_ops);
 extern struct kgdb_io *dbg_io_ops;
-- 
2.48.1.262.g85cc9f2d1e-goog



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