consoles: polling support, kgdboc

polled console handling support, to access a console in an irq-less
way while in debug or irq context.

absolutely zero impact as long as CONFIG_CONSOLE_POLL is disabled.
(which is the default)

[ jan.kiszka@siemens.com: lots of cleanups ]
[ mingo@elte.hu: redesign, splitups, cleanups. ]

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

8 files changed, 357 insertions, 3 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 613ec816ce60..4d3c7018f0c3 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1155,6 +1155,48 @@ static struct tty_driver *get_tty_driver(dev_t device, int *index)
         return NULL;
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+
+/**
+ *      tty_find_polling_driver -       find device of a polled tty
+ *      @name: name string to match
+ *      @line: pointer to resulting tty line nr
+ *
+ *      This routine returns a tty driver structure, given a name
+ *      and the condition that the tty driver is capable of polled
+ *      operation.
+ */
+struct tty_driver *tty_find_polling_driver(char *name, int *line)
+{
+        struct tty_driver *p, *res = NULL;
+        int tty_line = 0;
+        char *str;
+
+        mutex_lock(&tty_mutex);
+        /* Search through the tty devices to look for a match */
+        list_for_each_entry(p, &tty_drivers, tty_drivers) {
+                str = name + strlen(p->name);
+                tty_line = simple_strtoul(str, &str, 10);
+                if (*str == ',')
+                        str++;
+                if (*str == '\0')
+                        str = 0;
+
+                if (tty_line >= 0 && tty_line <= p->num && p->poll_init &&
+                                !p->poll_init(p, tty_line, str)) {
+
+                        res = p;
+                        *line = tty_line;
+                        break;
+                }
+        }
+        mutex_unlock(&tty_mutex);
+
+        return res;
+}
+EXPORT_SYMBOL_GPL(tty_find_polling_driver);
+#endif
+
 /**
  *      tty_check_change        -       check for POSIX terminal changes
  *      @tty: tty to check
@@ -3850,6 +3892,11 @@ void tty_set_operations(struct tty_driver *driver,
         driver->write_proc = op->write_proc;
         driver->tiocmget = op->tiocmget;
         driver->tiocmset = op->tiocmset;
+#ifdef CONFIG_CONSOLE_POLL
+        driver->poll_init = op->poll_init;
+        driver->poll_get_char = op->poll_get_char;
+        driver->poll_put_char = op->poll_put_char;
+#endif
 }
 
 
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 77f7a7f0646e..96a585e1cee8 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1740,6 +1740,60 @@ static inline void wait_for_xmitr(struct uart_8250_port *up, int bits)
         }
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+/*
+ * Console polling routines for writing and reading from the uart while
+ * in an interrupt or debug context.
+ */
+
+static int serial8250_get_poll_char(struct uart_port *port)
+{
+        struct uart_8250_port *up = (struct uart_8250_port *)port;
+        unsigned char lsr = serial_inp(up, UART_LSR);
+
+        while (!(lsr & UART_LSR_DR))
+                lsr = serial_inp(up, UART_LSR);
+
+        return serial_inp(up, UART_RX);
+}
+
+
+static void serial8250_put_poll_char(struct uart_port *port,
+                         unsigned char c)
+{
+        unsigned int ier;
+        struct uart_8250_port *up = (struct uart_8250_port *)port;
+
+        /*
+         *      First save the IER then disable the interrupts
+         */
+        ier = serial_in(up, UART_IER);
+        if (up->capabilities & UART_CAP_UUE)
+                serial_out(up, UART_IER, UART_IER_UUE);
+        else
+                serial_out(up, UART_IER, 0);
+
+        wait_for_xmitr(up, BOTH_EMPTY);
+        /*
+         *      Send the character out.
+         *      If a LF, also do CR...
+         */
+        serial_out(up, UART_TX, c);
+        if (c == 10) {
+                wait_for_xmitr(up, BOTH_EMPTY);
+                serial_out(up, UART_TX, 13);
+        }
+
+        /*
+         *      Finally, wait for transmitter to become empty
+         *      and restore the IER
+         */
+        wait_for_xmitr(up, BOTH_EMPTY);
+        serial_out(up, UART_IER, ier);
+}
+
+#endif /* CONFIG_CONSOLE_POLL */
+
 static int serial8250_startup(struct uart_port *port)
 {
         struct uart_8250_port *up = (struct uart_8250_port *)port;
@@ -2386,6 +2440,10 @@ static struct uart_ops serial8250_pops = {
         .request_port   = serial8250_request_port,
         .config_port    = serial8250_config_port,
         .verify_port    = serial8250_verify_port,
+#ifdef CONFIG_CONSOLE_POLL
+        .poll_get_char = serial8250_get_poll_char,
+        .poll_put_char = serial8250_put_poll_char,
+#endif
 };
 
 static struct uart_8250_port serial8250_ports[UART_NR];
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index cf627cd1b4c8..f7cd9504d811 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -961,6 +961,9 @@ config SERIAL_CORE
 config SERIAL_CORE_CONSOLE
         bool
 
+config CONSOLE_POLL
+        bool
+
 config SERIAL_68328
         bool "68328 serial support"
         depends on M68328 || M68EZ328 || M68VZ328
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index 640cfe44a56d..3cbea5494724 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -66,4 +66,5 @@ obj-$(CONFIG_SERIAL_UARTLITE) += uartlite.o
 obj-$(CONFIG_SERIAL_NETX) += netx-serial.o
 obj-$(CONFIG_SERIAL_OF_PLATFORM) += of_serial.o
 obj-$(CONFIG_SERIAL_KS8695) += serial_ks8695.o
+obj-$(CONFIG_KGDB_SERIAL_CONSOLE) += kgdboc.o
 obj-$(CONFIG_SERIAL_QE) += ucc_uart.o
diff --git a/drivers/serial/kgdboc.c b/drivers/serial/kgdboc.c
new file mode 100644
index 000000000000..341830791608
--- /dev/null
+++ b/drivers/serial/kgdboc.c
@@ -0,0 +1,163 @@
+/*
+ * Based on the same principle as kgdboe using the NETPOLL api, this
+ * driver uses a console polling api to implement a gdb serial inteface
+ * which is multiplexed on a console port.
+ *
+ * Maintainer: Jason Wessel <jason.wessel@windriver.com>
+ *
+ * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/kgdb.h>
+#include <linux/tty.h>
+
+#define MAX_CONFIG_LEN          40
+
+static struct kgdb_io           kgdboc_io_ops;
+
+/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
+static int configured           = -1;
+
+static char config[MAX_CONFIG_LEN];
+static struct kparam_string kps = {
+        .string                 = config,
+        .maxlen                 = MAX_CONFIG_LEN,
+};
+
+static struct tty_driver        *kgdb_tty_driver;
+static int                      kgdb_tty_line;
+
+static int kgdboc_option_setup(char *opt)
+{
+        if (strlen(opt) > MAX_CONFIG_LEN) {
+                printk(KERN_ERR "kgdboc: config string too long\n");
+                return -ENOSPC;
+        }
+        strcpy(config, opt);
+
+        return 0;
+}
+
+__setup("kgdboc=", kgdboc_option_setup);
+
+static int configure_kgdboc(void)
+{
+        struct tty_driver *p;
+        int tty_line = 0;
+        int err;
+
+        err = kgdboc_option_setup(config);
+        if (err || !strlen(config) || isspace(config[0]))
+                goto noconfig;
+
+        err = -ENODEV;
+
+        p = tty_find_polling_driver(config, &tty_line);
+        if (!p)
+                goto noconfig;
+
+        kgdb_tty_driver = p;
+        kgdb_tty_line = tty_line;
+
+        err = kgdb_register_io_module(&kgdboc_io_ops);
+        if (err)
+                goto noconfig;
+
+        configured = 1;
+
+        return 0;
+
+noconfig:
+        config[0] = 0;
+        configured = 0;
+
+        return err;
+}
+
+static int __init init_kgdboc(void)
+{
+        /* Already configured? */
+        if (configured == 1)
+                return 0;
+
+        return configure_kgdboc();
+}
+
+static void cleanup_kgdboc(void)
+{
+        if (configured == 1)
+                kgdb_unregister_io_module(&kgdboc_io_ops);
+}
+
+static int kgdboc_get_char(void)
+{
+        return kgdb_tty_driver->poll_get_char(kgdb_tty_driver, kgdb_tty_line);
+}
+
+static void kgdboc_put_char(u8 chr)
+{
+        kgdb_tty_driver->poll_put_char(kgdb_tty_driver, kgdb_tty_line, chr);
+}
+
+static int param_set_kgdboc_var(const char *kmessage, struct kernel_param *kp)
+{
+        if (strlen(kmessage) >= MAX_CONFIG_LEN) {
+                printk(KERN_ERR "kgdboc: config string too long\n");
+                return -ENOSPC;
+        }
+
+        /* Only copy in the string if the init function has not run yet */
+        if (configured < 0) {
+                strcpy(config, kmessage);
+                return 0;
+        }
+
+        if (kgdb_connected) {
+                printk(KERN_ERR
+                       "kgdboc: Cannot reconfigure while KGDB is connected.\n");
+
+                return -EBUSY;
+        }
+
+        strcpy(config, kmessage);
+
+        if (configured == 1)
+                cleanup_kgdboc();
+
+        /* Go and configure with the new params. */
+        return configure_kgdboc();
+}
+
+static void kgdboc_pre_exp_handler(void)
+{
+        /* Increment the module count when the debugger is active */
+        if (!kgdb_connected)
+                try_module_get(THIS_MODULE);
+}
+
+static void kgdboc_post_exp_handler(void)
+{
+        /* decrement the module count when the debugger detaches */
+        if (!kgdb_connected)
+                module_put(THIS_MODULE);
+}
+
+static struct kgdb_io kgdboc_io_ops = {
+        .name                   = "kgdboc",
+        .read_char              = kgdboc_get_char,
+        .write_char             = kgdboc_put_char,
+        .pre_exception          = kgdboc_pre_exp_handler,
+        .post_exception         = kgdboc_post_exp_handler,
+};
+
+module_init(init_kgdboc);
+module_exit(cleanup_kgdboc);
+module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
+MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
+MODULE_DESCRIPTION("KGDB Console TTY Driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 0f5a17987cca..4d7eecbead9b 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -1827,7 +1827,7 @@ uart_get_console(struct uart_port *ports, int nr, struct console *co)
  *      options.  The format of the string is <baud><parity><bits><flow>,
  *      eg: 115200n8r
  */
-void __init
+void
 uart_parse_options(char *options, int *baud, int *parity, int *bits, int *flow)
 {
         char *s = options;
@@ -1842,6 +1842,7 @@ uart_parse_options(char *options, int *baud, int *parity, int *bits, int *flow)
         if (*s)
                 *flow = *s;
 }
+EXPORT_SYMBOL_GPL(uart_parse_options);
 
 struct baud_rates {
         unsigned int rate;
@@ -1872,7 +1873,7 @@ static const struct baud_rates baud_rates[] = {
  *      @bits: number of data bits
  *      @flow: flow control character - 'r' (rts)
  */
-int __init
+int
 uart_set_options(struct uart_port *port, struct console *co,
                  int baud, int parity, int bits, int flow)
 {
@@ -1924,10 +1925,16 @@ uart_set_options(struct uart_port *port, struct console *co,
         port->mctrl |= TIOCM_DTR;
 
         port->ops->set_termios(port, &termios, &dummy);
-        co->cflag = termios.c_cflag;
+        /*
+         * Allow the setting of the UART parameters with a NULL console
+         * too:
+         */
+        if (co)
+                co->cflag = termios.c_cflag;
 
         return 0;
 }
+EXPORT_SYMBOL_GPL(uart_set_options);
 #endif /* CONFIG_SERIAL_CORE_CONSOLE */
 
 static void uart_change_pm(struct uart_state *state, int pm_state)
@@ -2182,6 +2189,60 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
         }
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+
+static int uart_poll_init(struct tty_driver *driver, int line, char *options)
+{
+        struct uart_driver *drv = driver->driver_state;
+        struct uart_state *state = drv->state + line;
+        struct uart_port *port;
+        int baud = 9600;
+        int bits = 8;
+        int parity = 'n';
+        int flow = 'n';
+
+        if (!state || !state->port)
+                return -1;
+
+        port = state->port;
+        if (!(port->ops->poll_get_char && port->ops->poll_put_char))
+                return -1;
+
+        if (options) {
+                uart_parse_options(options, &baud, &parity, &bits, &flow);
+                return uart_set_options(port, NULL, baud, parity, bits, flow);
+        }
+
+        return 0;
+}
+
+static int uart_poll_get_char(struct tty_driver *driver, int line)
+{
+        struct uart_driver *drv = driver->driver_state;
+        struct uart_state *state = drv->state + line;
+        struct uart_port *port;
+
+        if (!state || !state->port)
+                return -1;
+
+        port = state->port;
+        return port->ops->poll_get_char(port);
+}
+
+static void uart_poll_put_char(struct tty_driver *driver, int line, char ch)
+{
+        struct uart_driver *drv = driver->driver_state;
+        struct uart_state *state = drv->state + line;
+        struct uart_port *port;
+
+        if (!state || !state->port)
+                return;
+
+        port = state->port;
+        port->ops->poll_put_char(port, ch);
+}
+#endif
+
 static const struct tty_operations uart_ops = {
         .open           = uart_open,
         .close          = uart_close,
@@ -2206,6 +2267,11 @@ static const struct tty_operations uart_ops = {
 #endif
         .tiocmget       = uart_tiocmget,
         .tiocmset       = uart_tiocmset,
+#ifdef CONFIG_CONSOLE_POLL
+        .poll_init      = uart_poll_init,
+        .poll_get_char  = uart_poll_get_char,
+        .poll_put_char  = uart_poll_put_char,
+#endif
 };
 
 /**
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 289942fc6655..7cb094a82456 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -213,6 +213,10 @@ struct uart_ops {
         void            (*config_port)(struct uart_port *, int);
         int             (*verify_port)(struct uart_port *, struct serial_struct *);
         int             (*ioctl)(struct uart_port *, unsigned int, unsigned long);
+#ifdef CONFIG_CONSOLE_POLL
+        void    (*poll_put_char)(struct uart_port *, unsigned char);
+        int             (*poll_get_char)(struct uart_port *);
+#endif
 };
 
 #define UART_CONFIG_TYPE        (1 << 0)
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 85c95cd39bc3..21f69aca4505 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -125,6 +125,7 @@
 #include <linux/cdev.h>
 
 struct tty_struct;
+struct tty_driver;
 
 struct tty_operations {
         int  (*open)(struct tty_struct * tty, struct file * filp);
@@ -157,6 +158,11 @@ struct tty_operations {
         int (*tiocmget)(struct tty_struct *tty, struct file *file);
         int (*tiocmset)(struct tty_struct *tty, struct file *file,
                         unsigned int set, unsigned int clear);
+#ifdef CONFIG_CONSOLE_POLL
+        int (*poll_init)(struct tty_driver *driver, int line, char *options);
+        int (*poll_get_char)(struct tty_driver *driver, int line);
+        void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
+#endif
 };
 
 struct tty_driver {
@@ -220,6 +226,11 @@ struct tty_driver {
         int (*tiocmget)(struct tty_struct *tty, struct file *file);
         int (*tiocmset)(struct tty_struct *tty, struct file *file,
                         unsigned int set, unsigned int clear);
+#ifdef CONFIG_CONSOLE_POLL
+        int (*poll_init)(struct tty_driver *driver, int line, char *options);
+        int (*poll_get_char)(struct tty_driver *driver, int line);
+        void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
+#endif
 
         struct list_head tty_drivers;
 };
@@ -230,6 +241,7 @@ struct tty_driver *alloc_tty_driver(int lines);
 void put_tty_driver(struct tty_driver *driver);
 void tty_set_operations(struct tty_driver *driver,
                         const struct tty_operations *op);
+extern struct tty_driver *tty_find_polling_driver(char *name, int *line);
 
 /* tty driver magic number */
 #define TTY_DRIVER_MAGIC                0x5402