LinuxPPS: core support

This patch adds the kernel side of the PPS support currently named
"LinuxPPS".

PPS means "pulse per second" and a PPS source is just a device which
provides a high precision signal each second so that an application can
use it to adjust system clock time.

Common use is the combination of the NTPD as userland program with a GPS
receiver as PPS source to obtain a wallclock-time with sub-millisecond
synchronisation to UTC.

To obtain this goal the userland programs shoud use the PPS API
specification (RFC 2783 - Pulse-Per-Second API for UNIX-like Operating
Systems, Version 1.0) which in part is implemented by this patch.  It
provides a set of chars devices, one per PPS source, which can be used to
get the time signal.  The RFC's functions can be implemented by accessing
to these char devices.

Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

14 files changed, 1249 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-pps b/Documentation/ABI/testing/sysfs-pps
new file mode 100644
index 000000000000..25028c7bc37d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-pps
@@ -0,0 +1,73 @@
+What:           /sys/class/pps/
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ directory will contain files and
+                directories that will provide a unified interface to
+                the PPS sources.
+
+What:           /sys/class/pps/ppsX/
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ppsX/ directory is related to X-th
+                PPS source into the system. Each directory will
+                contain files to manage and control its PPS source.
+
+What:           /sys/class/pps/ppsX/assert
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ppsX/assert file reports the assert events
+                and the assert sequence number of the X-th source in the form:
+
+                        <secs>.<nsec>#<sequence>
+
+                If the source has no assert events the content of this file
+                is empty.
+
+What:           /sys/class/pps/ppsX/clear
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ppsX/clear file reports the clear events
+                and the clear sequence number of the X-th source in the form:
+
+                        <secs>.<nsec>#<sequence>
+
+                If the source has no clear events the content of this file
+                is empty.
+
+What:           /sys/class/pps/ppsX/mode
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ppsX/mode file reports the functioning
+                mode of the X-th source in hexadecimal encoding.
+
+                Please, refer to linux/include/linux/pps.h for further
+                info.
+
+What:           /sys/class/pps/ppsX/echo
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ppsX/echo file reports if the X-th does
+                or does not support an "echo" function.
+
+What:           /sys/class/pps/ppsX/name
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ppsX/name file reports the name of the
+                X-th source.
+
+What:           /sys/class/pps/ppsX/path
+Date:           February 2008
+Contact:        Rodolfo Giometti <giometti@linux.it>
+Description:
+                The /sys/class/pps/ppsX/path file reports the path name of
+                the device connected with the X-th source.
+
+                If the source is not connected with any device the content
+                of this file is empty.
diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index 1f779a25c703..7bb0d934b6d8 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -149,6 +149,8 @@ Code	Seq#	Include File		Comments
 'p'     40-7F   linux/nvram.h
 'p'     80-9F                           user-space parport
                                         <mailto:tim@cyberelk.net>
+'p'     a1-a4   linux/pps.h             LinuxPPS
+                                        <mailto:giometti@linux.it>
 'q'     00-1F   linux/serio.h
 'q'     80-FF                           Internet PhoneJACK, Internet LineJACK
                                         <http://www.quicknet.net>
diff --git a/Documentation/pps/pps.txt b/Documentation/pps/pps.txt
new file mode 100644
index 000000000000..125f4ab48998
--- /dev/null
+++ b/Documentation/pps/pps.txt
@@ -0,0 +1,172 @@
+
+                        PPS - Pulse Per Second
+                        ----------------------
+
+(C) Copyright 2007 Rodolfo Giometti <giometti@enneenne.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+
+
+Overview
+--------
+
+LinuxPPS provides a programming interface (API) to define in the
+system several PPS sources.
+
+PPS means "pulse per second" and a PPS source is just a device which
+provides a high precision signal each second so that an application
+can use it to adjust system clock time.
+
+A PPS source can be connected to a serial port (usually to the Data
+Carrier Detect pin) or to a parallel port (ACK-pin) or to a special
+CPU's GPIOs (this is the common case in embedded systems) but in each
+case when a new pulse arrives the system must apply to it a timestamp
+and record it for userland.
+
+Common use is the combination of the NTPD as userland program, with a
+GPS receiver as PPS source, to obtain a wallclock-time with
+sub-millisecond synchronisation to UTC.
+
+
+RFC considerations
+------------------
+
+While implementing a PPS API as RFC 2783 defines and using an embedded
+CPU GPIO-Pin as physical link to the signal, I encountered a deeper
+problem:
+
+   At startup it needs a file descriptor as argument for the function
+   time_pps_create().
+
+This implies that the source has a /dev/... entry. This assumption is
+ok for the serial and parallel port, where you can do something
+useful besides(!) the gathering of timestamps as it is the central
+task for a PPS-API. But this assumption does not work for a single
+purpose GPIO line. In this case even basic file-related functionality
+(like read() and write()) makes no sense at all and should not be a
+precondition for the use of a PPS-API.
+
+The problem can be simply solved if you consider that a PPS source is
+not always connected with a GPS data source.
+
+So your programs should check if the GPS data source (the serial port
+for instance) is a PPS source too, and if not they should provide the
+possibility to open another device as PPS source.
+
+In LinuxPPS the PPS sources are simply char devices usually mapped
+into files /dev/pps0, /dev/pps1, etc..
+
+
+Coding example
+--------------
+
+To register a PPS source into the kernel you should define a struct
+pps_source_info_s as follows:
+
+    static struct pps_source_info pps_ktimer_info = {
+            .name         = "ktimer",
+            .path         = "",
+            .mode         = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | \
+                            PPS_ECHOASSERT | \
+                            PPS_CANWAIT | PPS_TSFMT_TSPEC,
+            .echo         = pps_ktimer_echo,
+            .owner        = THIS_MODULE,
+    };
+
+and then calling the function pps_register_source() in your
+intialization routine as follows:
+
+    source = pps_register_source(&pps_ktimer_info,
+                        PPS_CAPTUREASSERT | PPS_OFFSETASSERT);
+
+The pps_register_source() prototype is:
+
+  int pps_register_source(struct pps_source_info_s *info, int default_params)
+
+where "info" is a pointer to a structure that describes a particular
+PPS source, "default_params" tells the system what the initial default
+parameters for the device should be (it is obvious that these parameters
+must be a subset of ones defined in the struct
+pps_source_info_s which describe the capabilities of the driver).
+
+Once you have registered a new PPS source into the system you can
+signal an assert event (for example in the interrupt handler routine)
+just using:
+
+    pps_event(source, &ts, PPS_CAPTUREASSERT, ptr)
+
+where "ts" is the event's timestamp.
+
+The same function may also run the defined echo function
+(pps_ktimer_echo(), passing to it the "ptr" pointer) if the user
+asked for that... etc..
+
+Please see the file drivers/pps/clients/ktimer.c for example code.
+
+
+SYSFS support
+-------------
+
+If the SYSFS filesystem is enabled in the kernel it provides a new class:
+
+   $ ls /sys/class/pps/
+   pps0/  pps1/  pps2/
+
+Every directory is the ID of a PPS sources defined in the system and
+inside you find several files:
+
+   $ ls /sys/class/pps/pps0/
+   assert       clear  echo  mode  name  path  subsystem@  uevent
+
+Inside each "assert" and "clear" file you can find the timestamp and a
+sequence number:
+
+   $ cat /sys/class/pps/pps0/assert
+   1170026870.983207967#8
+
+Where before the "#" is the timestamp in seconds; after it is the
+sequence number. Other files are:
+
+* echo: reports if the PPS source has an echo function or not;
+
+* mode: reports available PPS functioning modes;
+
+* name: reports the PPS source's name;
+
+* path: reports the PPS source's device path, that is the device the
+  PPS source is connected to (if it exists).
+
+
+Testing the PPS support
+-----------------------
+
+In order to test the PPS support even without specific hardware you can use
+the ktimer driver (see the client subsection in the PPS configuration menu)
+and the userland tools provided into Documentaion/pps/ directory.
+
+Once you have enabled the compilation of ktimer just modprobe it (if
+not statically compiled):
+
+   # modprobe ktimer
+
+and the run ppstest as follow:
+
+   $ ./ppstest /dev/pps0
+   trying PPS source "/dev/pps1"
+   found PPS source "/dev/pps1"
+   ok, found 1 source(s), now start fetching data...
+   source 0 - assert 1186592699.388832443, sequence: 364 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592700.388931295, sequence: 365 - clear  0.000000000, sequence: 0
+   source 0 - assert 1186592701.389032765, sequence: 366 - clear  0.000000000, sequence: 0
+
+Please, note that to compile userland programs you need the file timepps.h
+(see Documentation/pps/).
diff --git a/MAINTAINERS b/MAINTAINERS
index 5b7a08d88e4f..035df9d26609 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4577,6 +4577,13 @@ S:	Maintained
 F:      drivers/net/pppol2tp.c
 F:      include/linux/if_pppol2tp.h
 
+PPS SUPPORT
+P:      Rodolfo Giometti
+M:      giometti@enneenne.com
+W:      http://wiki.enneenne.com/index.php/LinuxPPS_support
+L:      linuxpps@ml.enneenne.com (subscribers-only)
+S:      Maintained
+
 PREEMPTIBLE KERNEL
 P:      Robert Love
 M:      rml@tech9.net
diff --git a/drivers/Kconfig b/drivers/Kconfig
index a442c8f29fc1..48bbdbe43e69 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -52,6 +52,8 @@ source "drivers/i2c/Kconfig"
 
 source "drivers/spi/Kconfig"
 
+source "drivers/pps/Kconfig"
+
 source "drivers/gpio/Kconfig"
 
 source "drivers/w1/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index 00b44f4ccf03..bc4205d2fc3c 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -72,6 +72,7 @@ obj-$(CONFIG_INPUT)		+= input/
 obj-$(CONFIG_I2O)               += message/
 obj-$(CONFIG_RTC_LIB)           += rtc/
 obj-y                           += i2c/ media/
+obj-$(CONFIG_PPS)               += pps/
 obj-$(CONFIG_W1)                += w1/
 obj-$(CONFIG_POWER_SUPPLY)      += power/
 obj-$(CONFIG_HWMON)             += hwmon/
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
new file mode 100644
index 000000000000..cc2eb8edb514
--- /dev/null
+++ b/drivers/pps/Kconfig
@@ -0,0 +1,33 @@
+#
+# PPS support configuration
+#
+
+menu "PPS support"
+
+config PPS
+        tristate "PPS support"
+        depends on EXPERIMENTAL
+        ---help---
+          PPS (Pulse Per Second) is a special pulse provided by some GPS
+          antennae. Userland can use it to get a high-precision time
+          reference.
+
+          Some antennae's PPS signals are connected with the CD (Carrier
+          Detect) pin of the serial line they use to communicate with the
+          host. In this case use the SERIAL_LINE client support.
+
+          Some antennae's PPS signals are connected with some special host
+          inputs so you have to enable the corresponding client support.
+
+          To compile this driver as a module, choose M here: the module
+          will be called pps_core.ko.
+
+config PPS_DEBUG
+        bool "PPS debugging messages"
+        depends on PPS
+        help
+          Say Y here if you want the PPS support to produce a bunch of debug
+          messages to the system log.  Select this if you are having a
+          problem with PPS support and want to see more of what is going on.
+
+endmenu
diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
new file mode 100644
index 000000000000..19ea582f431d
--- /dev/null
+++ b/drivers/pps/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for the PPS core.
+#
+
+pps_core-y                      := pps.o kapi.o sysfs.o
+obj-$(CONFIG_PPS)               := pps_core.o
+
+ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
new file mode 100644
index 000000000000..35a0b192d768
--- /dev/null
+++ b/drivers/pps/kapi.c
@@ -0,0 +1,329 @@
+/*
+ * kernel API
+ *
+ *
+ * Copyright (C) 2005-2009   Rodolfo Giometti <giometti@linux.it>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+#include <linux/fs.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Global variables
+ */
+
+DEFINE_SPINLOCK(pps_idr_lock);
+DEFINE_IDR(pps_idr);
+
+/*
+ * Local functions
+ */
+
+static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
+{
+        ts->nsec += offset->nsec;
+        while (ts->nsec >= NSEC_PER_SEC) {
+                ts->nsec -= NSEC_PER_SEC;
+                ts->sec++;
+        }
+        while (ts->nsec < 0) {
+                ts->nsec += NSEC_PER_SEC;
+                ts->sec--;
+        }
+        ts->sec += offset->sec;
+}
+
+/*
+ * Exported functions
+ */
+
+/* pps_get_source - find a PPS source
+ * @source: the PPS source ID.
+ *
+ * This function is used to find an already registered PPS source into the
+ * system.
+ *
+ * The function returns NULL if found nothing, otherwise it returns a pointer
+ * to the PPS source data struct (the refcounter is incremented by 1).
+ */
+
+struct pps_device *pps_get_source(int source)
+{
+        struct pps_device *pps;
+        unsigned long flags;
+
+        spin_lock_irqsave(&pps_idr_lock, flags);
+
+        pps = idr_find(&pps_idr, source);
+        if (pps != NULL)
+                atomic_inc(&pps->usage);
+
+        spin_unlock_irqrestore(&pps_idr_lock, flags);
+
+        return pps;
+}
+
+/* pps_put_source - free the PPS source data
+ * @pps: a pointer to the PPS source.
+ *
+ * This function is used to free a PPS data struct if its refcount is 0.
+ */
+
+void pps_put_source(struct pps_device *pps)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&pps_idr_lock, flags);
+        BUG_ON(atomic_read(&pps->usage) == 0);
+
+        if (!atomic_dec_and_test(&pps->usage)) {
+                pps = NULL;
+                goto exit;
+        }
+
+        /* No more reference to the PPS source. We can safely remove the
+         * PPS data struct.
+         */
+        idr_remove(&pps_idr, pps->id);
+
+exit:
+        spin_unlock_irqrestore(&pps_idr_lock, flags);
+        kfree(pps);
+}
+
+/* pps_register_source - add a PPS source in the system
+ * @info: the PPS info struct
+ * @default_params: the default PPS parameters of the new source
+ *
+ * This function is used to add a new PPS source in the system. The new
+ * source is described by info's fields and it will have, as default PPS
+ * parameters, the ones specified into default_params.
+ *
+ * The function returns, in case of success, the PPS source ID.
+ */
+
+int pps_register_source(struct pps_source_info *info, int default_params)
+{
+        struct pps_device *pps;
+        int id;
+        int err;
+
+        /* Sanity checks */
+        if ((info->mode & default_params) != default_params) {
+                printk(KERN_ERR "pps: %s: unsupported default parameters\n",
+                                        info->name);
+                err = -EINVAL;
+                goto pps_register_source_exit;
+        }
+        if ((info->mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
+                        info->echo == NULL) {
+                printk(KERN_ERR "pps: %s: echo function is not defined\n",
+                                        info->name);
+                err = -EINVAL;
+                goto pps_register_source_exit;
+        }
+        if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+                printk(KERN_ERR "pps: %s: unspecified time format\n",
+                                        info->name);
+                err = -EINVAL;
+                goto pps_register_source_exit;
+        }
+
+        /* Allocate memory for the new PPS source struct */
+        pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL);
+        if (pps == NULL) {
+                err = -ENOMEM;
+                goto pps_register_source_exit;
+        }
+
+        /* These initializations must be done before calling idr_get_new()
+         * in order to avoid reces into pps_event().
+         */
+        pps->params.api_version = PPS_API_VERS;
+        pps->params.mode = default_params;
+        pps->info = *info;
+
+        init_waitqueue_head(&pps->queue);
+        spin_lock_init(&pps->lock);
+        atomic_set(&pps->usage, 1);
+
+        /* Get new ID for the new PPS source */
+        if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
+                err = -ENOMEM;
+                goto kfree_pps;
+        }
+
+        spin_lock_irq(&pps_idr_lock);
+
+        /* Now really allocate the PPS source.
+         * After idr_get_new() calling the new source will be freely available
+         * into the kernel.
+         */
+        err = idr_get_new(&pps_idr, pps, &id);
+        if (err < 0) {
+                spin_unlock_irq(&pps_idr_lock);
+                goto kfree_pps;
+        }
+
+        id = id & MAX_ID_MASK;
+        if (id >= PPS_MAX_SOURCES) {
+                spin_unlock_irq(&pps_idr_lock);
+
+                printk(KERN_ERR "pps: %s: too many PPS sources in the system\n",
+                                        info->name);
+                err = -EBUSY;
+                goto free_idr;
+        }
+        pps->id = id;
+
+        spin_unlock_irq(&pps_idr_lock);
+
+        /* Create the char device */
+        err = pps_register_cdev(pps);
+        if (err < 0) {
+                printk(KERN_ERR "pps: %s: unable to create char device\n",
+                                        info->name);
+                goto free_idr;
+        }
+
+        pr_info("new PPS source %s at ID %d\n", info->name, id);
+
+        return id;
+
+free_idr:
+        spin_lock_irq(&pps_idr_lock);
+        idr_remove(&pps_idr, id);
+        spin_unlock_irq(&pps_idr_lock);
+
+kfree_pps:
+        kfree(pps);
+
+pps_register_source_exit:
+        printk(KERN_ERR "pps: %s: unable to register source\n", info->name);
+
+        return err;
+}
+EXPORT_SYMBOL(pps_register_source);
+
+/* pps_unregister_source - remove a PPS source from the system
+ * @source: the PPS source ID
+ *
+ * This function is used to remove a previously registered PPS source from
+ * the system.
+ */
+
+void pps_unregister_source(int source)
+{
+        struct pps_device *pps;
+
+        spin_lock_irq(&pps_idr_lock);
+        pps = idr_find(&pps_idr, source);
+
+        if (!pps) {
+                BUG();
+                spin_unlock_irq(&pps_idr_lock);
+                return;
+        }
+        spin_unlock_irq(&pps_idr_lock);
+
+        pps_unregister_cdev(pps);
+        pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_unregister_source);
+
+/* pps_event - register a PPS event into the system
+ * @source: the PPS source ID
+ * @ts: the event timestamp
+ * @event: the event type
+ * @data: userdef pointer
+ *
+ * This function is used by each PPS client in order to register a new
+ * PPS event into the system (it's usually called inside an IRQ handler).
+ *
+ * If an echo function is associated with the PPS source it will be called
+ * as:
+ *      pps->info.echo(source, event, data);
+ */
+
+void pps_event(int source, struct pps_ktime *ts, int event, void *data)
+{
+        struct pps_device *pps;
+        unsigned long flags;
+
+        if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
+                printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
+                        event, source);
+                return;
+        }
+
+        pps = pps_get_source(source);
+        if (!pps)
+                return;
+
+        pr_debug("PPS event on source %d at %llu.%06u\n",
+                        pps->id, (unsigned long long) ts->sec, ts->nsec);
+
+        spin_lock_irqsave(&pps->lock, flags);
+
+        /* Must call the echo function? */
+        if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
+                pps->info.echo(source, event, data);
+
+        /* Check the event */
+        pps->current_mode = pps->params.mode;
+        if (event & PPS_CAPTUREASSERT) {
+                /* We have to add an offset? */
+                if (pps->params.mode & PPS_OFFSETASSERT)
+                        pps_add_offset(ts, &pps->params.assert_off_tu);
+
+                /* Save the time stamp */
+                pps->assert_tu = *ts;
+                pps->assert_sequence++;
+                pr_debug("capture assert seq #%u for source %d\n",
+                        pps->assert_sequence, source);
+        }
+        if (event & PPS_CAPTURECLEAR) {
+                /* We have to add an offset? */
+                if (pps->params.mode & PPS_OFFSETCLEAR)
+                        pps_add_offset(ts, &pps->params.clear_off_tu);
+
+                /* Save the time stamp */
+                pps->clear_tu = *ts;
+                pps->clear_sequence++;
+                pr_debug("capture clear seq #%u for source %d\n",
+                        pps->clear_sequence, source);
+        }
+
+        pps->go = ~0;
+        wake_up_interruptible(&pps->queue);
+
+        kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
+
+        spin_unlock_irqrestore(&pps->lock, flags);
+
+        /* Now we can release the PPS source for (possible) deregistration */
+        pps_put_source(pps);
+}
+EXPORT_SYMBOL(pps_event);
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
new file mode 100644
index 000000000000..ac8cc8cea1e3
--- /dev/null
+++ b/drivers/pps/pps.c
@@ -0,0 +1,312 @@
+/*
+ * PPS core file
+ *
+ *
+ * Copyright (C) 2005-2009   Rodolfo Giometti <giometti@linux.it>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+#include <linux/idr.h>
+#include <linux/cdev.h>
+#include <linux/poll.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Local variables
+ */
+
+static dev_t pps_devt;
+static struct class *pps_class;
+
+/*
+ * Char device methods
+ */
+
+static unsigned int pps_cdev_poll(struct file *file, poll_table *wait)
+{
+        struct pps_device *pps = file->private_data;
+
+        poll_wait(file, &pps->queue, wait);
+
+        return POLLIN | POLLRDNORM;
+}
+
+static int pps_cdev_fasync(int fd, struct file *file, int on)
+{
+        struct pps_device *pps = file->private_data;
+        return fasync_helper(fd, file, on, &pps->async_queue);
+}
+
+static long pps_cdev_ioctl(struct file *file,
+                unsigned int cmd, unsigned long arg)
+{
+        struct pps_device *pps = file->private_data;
+        struct pps_kparams params;
+        struct pps_fdata fdata;
+        unsigned long ticks;
+        void __user *uarg = (void __user *) arg;
+        int __user *iuarg = (int __user *) arg;
+        int err;
+
+        switch (cmd) {
+        case PPS_GETPARAMS:
+                pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
+
+                /* Return current parameters */
+                err = copy_to_user(uarg, &pps->params,
+                                                sizeof(struct pps_kparams));
+                if (err)
+                        return -EFAULT;
+
+                break;
+
+        case PPS_SETPARAMS:
+                pr_debug("PPS_SETPARAMS: source %d\n", pps->id);
+
+                /* Check the capabilities */
+                if (!capable(CAP_SYS_TIME))
+                        return -EPERM;
+
+                err = copy_from_user(&params, uarg, sizeof(struct pps_kparams));
+                if (err)
+                        return -EFAULT;
+                if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
+                        pr_debug("capture mode unspecified (%x)\n",
+                                                                params.mode);
+                        return -EINVAL;
+                }
+
+                /* Check for supported capabilities */
+                if ((params.mode & ~pps->info.mode) != 0) {
+                        pr_debug("unsupported capabilities (%x)\n",
+                                                                params.mode);
+                        return -EINVAL;
+                }
+
+                spin_lock_irq(&pps->lock);
+
+                /* Save the new parameters */
+                pps->params = params;
+
+                /* Restore the read only parameters */
+                if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
+                        /* section 3.3 of RFC 2783 interpreted */
+                        pr_debug("time format unspecified (%x)\n",
+                                                                params.mode);
+                        pps->params.mode |= PPS_TSFMT_TSPEC;
+                }
+                if (pps->info.mode & PPS_CANWAIT)
+                        pps->params.mode |= PPS_CANWAIT;
+                pps->params.api_version = PPS_API_VERS;
+
+                spin_unlock_irq(&pps->lock);
+
+                break;
+
+        case PPS_GETCAP:
+                pr_debug("PPS_GETCAP: source %d\n", pps->id);
+
+                err = put_user(pps->info.mode, iuarg);
+                if (err)
+                        return -EFAULT;
+
+                break;
+
+        case PPS_FETCH:
+                pr_debug("PPS_FETCH: source %d\n", pps->id);
+
+                err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
+                if (err)
+                        return -EFAULT;
+
+                pps->go = 0;
+
+                /* Manage the timeout */
+                if (fdata.timeout.flags & PPS_TIME_INVALID)
+                        err = wait_event_interruptible(pps->queue, pps->go);
+                else {
+                        pr_debug("timeout %lld.%09d\n",
+                                        (long long) fdata.timeout.sec,
+                                        fdata.timeout.nsec);
+                        ticks = fdata.timeout.sec * HZ;
+                        ticks += fdata.timeout.nsec / (NSEC_PER_SEC / HZ);
+
+                        if (ticks != 0) {
+                                err = wait_event_interruptible_timeout(
+                                                pps->queue, pps->go, ticks);
+                                if (err == 0)
+                                        return -ETIMEDOUT;
+                        }
+                }
+
+                /* Check for pending signals */
+                if (err == -ERESTARTSYS) {
+                        pr_debug("pending signal caught\n");
+                        return -EINTR;
+                }
+
+                /* Return the fetched timestamp */
+                spin_lock_irq(&pps->lock);
+
+                fdata.info.assert_sequence = pps->assert_sequence;
+                fdata.info.clear_sequence = pps->clear_sequence;
+                fdata.info.assert_tu = pps->assert_tu;
+                fdata.info.clear_tu = pps->clear_tu;
+                fdata.info.current_mode = pps->current_mode;
+
+                spin_unlock_irq(&pps->lock);
+
+                err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata));
+                if (err)
+                        return -EFAULT;
+
+                break;
+
+        default:
+                return -ENOTTY;
+                break;
+        }
+
+        return 0;
+}
+
+static int pps_cdev_open(struct inode *inode, struct file *file)
+{
+        struct pps_device *pps = container_of(inode->i_cdev,
+                                                struct pps_device, cdev);
+        int found;
+
+        found = pps_get_source(pps->id) != 0;
+        if (!found)
+                return -ENODEV;
+
+        file->private_data = pps;
+
+        return 0;
+}
+
+static int pps_cdev_release(struct inode *inode, struct file *file)
+{
+        struct pps_device *pps = file->private_data;
+
+        /* Free the PPS source and wake up (possible) deregistration */
+        pps_put_source(pps);
+
+        return 0;
+}
+
+/*
+ * Char device stuff
+ */
+
+static const struct file_operations pps_cdev_fops = {
+        .owner          = THIS_MODULE,
+        .llseek         = no_llseek,
+        .poll           = pps_cdev_poll,
+        .fasync         = pps_cdev_fasync,
+        .unlocked_ioctl = pps_cdev_ioctl,
+        .open           = pps_cdev_open,
+        .release        = pps_cdev_release,
+};
+
+int pps_register_cdev(struct pps_device *pps)
+{
+        int err;
+
+        pps->devno = MKDEV(MAJOR(pps_devt), pps->id);
+        cdev_init(&pps->cdev, &pps_cdev_fops);
+        pps->cdev.owner = pps->info.owner;
+
+        err = cdev_add(&pps->cdev, pps->devno, 1);
+        if (err) {
+                printk(KERN_ERR "pps: %s: failed to add char device %d:%d\n",
+                                pps->info.name, MAJOR(pps_devt), pps->id);
+                return err;
+        }
+        pps->dev = device_create(pps_class, pps->info.dev, pps->devno, NULL,
+                                                        "pps%d", pps->id);
+        if (err)
+                goto del_cdev;
+        dev_set_drvdata(pps->dev, pps);
+
+        pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
+                        MAJOR(pps_devt), pps->id);
+
+        return 0;
+
+del_cdev:
+        cdev_del(&pps->cdev);
+
+        return err;
+}
+
+void pps_unregister_cdev(struct pps_device *pps)
+{
+        device_destroy(pps_class, pps->devno);
+        cdev_del(&pps->cdev);
+}
+
+/*
+ * Module stuff
+ */
+
+static void __exit pps_exit(void)
+{
+        class_destroy(pps_class);
+        unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
+}
+
+static int __init pps_init(void)
+{
+        int err;
+
+        pps_class = class_create(THIS_MODULE, "pps");
+        if (!pps_class) {
+                printk(KERN_ERR "pps: failed to allocate class\n");
+                return -ENOMEM;
+        }
+        pps_class->dev_attrs = pps_attrs;
+
+        err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
+        if (err < 0) {
+                printk(KERN_ERR "pps: failed to allocate char device region\n");
+                goto remove_class;
+        }
+
+        pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
+        pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
+                "<giometti@linux.it>\n", PPS_VERSION);
+
+        return 0;
+
+remove_class:
+        class_destroy(pps_class);
+
+        return err;
+}
+
+subsys_initcall(pps_init);
+module_exit(pps_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("LinuxPPS support (RFC 2783) - ver. " PPS_VERSION);
+MODULE_LICENSE("GPL");
diff --git a/drivers/pps/sysfs.c b/drivers/pps/sysfs.c
new file mode 100644
index 000000000000..ef0978c71eee
--- /dev/null
+++ b/drivers/pps/sysfs.c
@@ -0,0 +1,98 @@
+/*
+ * PPS sysfs support
+ *
+ *
+ * Copyright (C) 2007-2009   Rodolfo Giometti <giometti@linux.it>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/pps_kernel.h>
+
+/*
+ * Attribute functions
+ */
+
+static ssize_t pps_show_assert(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        if (!(pps->info.mode & PPS_CAPTUREASSERT))
+                return 0;
+
+        return sprintf(buf, "%lld.%09d#%d\n",
+                        (long long) pps->assert_tu.sec, pps->assert_tu.nsec,
+                        pps->assert_sequence);
+}
+
+static ssize_t pps_show_clear(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        if (!(pps->info.mode & PPS_CAPTURECLEAR))
+                return 0;
+
+        return sprintf(buf, "%lld.%09d#%d\n",
+                        (long long) pps->clear_tu.sec, pps->clear_tu.nsec,
+                        pps->clear_sequence);
+}
+
+static ssize_t pps_show_mode(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%4x\n", pps->info.mode);
+}
+
+static ssize_t pps_show_echo(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%d\n", !!pps->info.echo);
+}
+
+static ssize_t pps_show_name(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%s\n", pps->info.name);
+}
+
+static ssize_t pps_show_path(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct pps_device *pps = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%s\n", pps->info.path);
+}
+
+struct device_attribute pps_attrs[] = {
+        __ATTR(assert, S_IRUGO, pps_show_assert, NULL),
+        __ATTR(clear, S_IRUGO, pps_show_clear, NULL),
+        __ATTR(mode, S_IRUGO, pps_show_mode, NULL),
+        __ATTR(echo, S_IRUGO, pps_show_echo, NULL),
+        __ATTR(name, S_IRUGO, pps_show_name, NULL),
+        __ATTR(path, S_IRUGO, pps_show_path, NULL),
+        __ATTR_NULL,
+};
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index a2df7030d49d..03f22076381f 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -308,6 +308,7 @@ unifdef-y += pmu.h
 unifdef-y += poll.h
 unifdef-y += ppp_defs.h
 unifdef-y += ppp-comp.h
+unifdef-y += pps.h
 unifdef-y += ptrace.h
 unifdef-y += quota.h
 unifdef-y += random.h
diff --git a/include/linux/pps.h b/include/linux/pps.h
new file mode 100644
index 000000000000..cfe5c7214ec6
--- /dev/null
+++ b/include/linux/pps.h
@@ -0,0 +1,122 @@
+/*
+ * PPS API header
+ *
+ * Copyright (C) 2005-2009   Rodolfo Giometti <giometti@linux.it>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#ifndef _PPS_H_
+#define _PPS_H_
+
+#define PPS_VERSION             "5.3.6"
+#define PPS_MAX_SOURCES         16              /* should be enough... */
+
+/* Implementation note: the logical states ``assert'' and ``clear''
+ * are implemented in terms of the chip register, i.e. ``assert''
+ * means the bit is set.  */
+
+/*
+ * 3.2 New data structures
+ */
+
+#define PPS_API_VERS_1          1
+#define PPS_API_VERS            PPS_API_VERS_1  /* we use API version 1 */
+#define PPS_MAX_NAME_LEN        32
+
+/* 32-bit vs. 64-bit compatibility.
+ *
+ * 0n i386, the alignment of a uint64_t is only 4 bytes, while on most other
+ * architectures it's 8 bytes. On i386, there will be no padding between the
+ * two consecutive 'struct pps_ktime' members of struct pps_kinfo and struct
+ * pps_kparams. But on most platforms there will be padding to ensure correct
+ * alignment.
+ *
+ * The simple fix is probably to add an explicit padding.
+ *                                                      [David Woodhouse]
+ */
+struct pps_ktime {
+        __s64 sec;
+        __s32 nsec;
+        __u32 flags;
+};
+#define PPS_TIME_INVALID        (1<<0)  /* used to specify timeout==NULL */
+
+struct pps_kinfo {
+        __u32 assert_sequence;          /* seq. num. of assert event */
+        __u32 clear_sequence;           /* seq. num. of clear event */
+        struct pps_ktime assert_tu;     /* time of assert event */
+        struct pps_ktime clear_tu;      /* time of clear event */
+        int current_mode;               /* current mode bits */
+};
+
+struct pps_kparams {
+        int api_version;                /* API version # */
+        int mode;                       /* mode bits */
+        struct pps_ktime assert_off_tu; /* offset compensation for assert */
+        struct pps_ktime clear_off_tu;  /* offset compensation for clear */
+};
+
+/*
+ * 3.3 Mode bit definitions
+ */
+
+/* Device/implementation parameters */
+#define PPS_CAPTUREASSERT       0x01    /* capture assert events */
+#define PPS_CAPTURECLEAR        0x02    /* capture clear events */
+#define PPS_CAPTUREBOTH         0x03    /* capture assert and clear events */
+
+#define PPS_OFFSETASSERT        0x10    /* apply compensation for assert ev. */
+#define PPS_OFFSETCLEAR         0x20    /* apply compensation for clear ev. */
+
+#define PPS_CANWAIT             0x100   /* can we wait for an event? */
+#define PPS_CANPOLL             0x200   /* bit reserved for future use */
+
+/* Kernel actions */
+#define PPS_ECHOASSERT          0x40    /* feed back assert event to output */
+#define PPS_ECHOCLEAR           0x80    /* feed back clear event to output */
+
+/* Timestamp formats */
+#define PPS_TSFMT_TSPEC         0x1000  /* select timespec format */
+#define PPS_TSFMT_NTPFP         0x2000  /* select NTP format */
+
+/*
+ * 3.4.4 New functions: disciplining the kernel timebase
+ */
+
+/* Kernel consumers */
+#define PPS_KC_HARDPPS          0       /* hardpps() (or equivalent) */
+#define PPS_KC_HARDPPS_PLL      1       /* hardpps() constrained to
+                                           use a phase-locked loop */
+#define PPS_KC_HARDPPS_FLL      2       /* hardpps() constrained to
+                                           use a frequency-locked loop */
+/*
+ * Here begins the implementation-specific part!
+ */
+
+struct pps_fdata {
+        struct pps_kinfo info;
+        struct pps_ktime timeout;
+};
+
+#include <linux/ioctl.h>
+
+#define PPS_GETPARAMS           _IOR('p', 0xa1, struct pps_kparams *)
+#define PPS_SETPARAMS           _IOW('p', 0xa2, struct pps_kparams *)
+#define PPS_GETCAP              _IOR('p', 0xa3, int *)
+#define PPS_FETCH               _IOWR('p', 0xa4, struct pps_fdata *)
+
+#endif /* _PPS_H_ */
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
new file mode 100644
index 000000000000..e0a193f830ef
--- /dev/null
+++ b/include/linux/pps_kernel.h
@@ -0,0 +1,89 @@
+/*
+ * PPS API kernel header
+ *
+ * Copyright (C) 2009   Rodolfo Giometti <giometti@linux.it>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/pps.h>
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/time.h>
+
+/*
+ * Global defines
+ */
+
+/* The specific PPS source info */
+struct pps_source_info {
+        char name[PPS_MAX_NAME_LEN];            /* simbolic name */
+        char path[PPS_MAX_NAME_LEN];            /* path of connected device */
+        int mode;                               /* PPS's allowed mode */
+
+        void (*echo)(int source, int event, void *data); /* PPS echo function */
+
+        struct module *owner;
+        struct device *dev;
+};
+
+/* The main struct */
+struct pps_device {
+        struct pps_source_info info;            /* PSS source info */
+
+        struct pps_kparams params;              /* PPS's current params */
+
+        __u32 assert_sequence;                  /* PPS' assert event seq # */
+        __u32 clear_sequence;                   /* PPS' clear event seq # */
+        struct pps_ktime assert_tu;
+        struct pps_ktime clear_tu;
+        int current_mode;                       /* PPS mode at event time */
+
+        int go;                                 /* PPS event is arrived? */
+        wait_queue_head_t queue;                /* PPS event queue */
+
+        unsigned int id;                        /* PPS source unique ID */
+        struct cdev cdev;
+        struct device *dev;
+        int devno;
+        struct fasync_struct *async_queue;      /* fasync method */
+        spinlock_t lock;
+
+        atomic_t usage;                         /* usage count */
+};
+
+/*
+ * Global variables
+ */
+
+extern spinlock_t pps_idr_lock;
+extern struct idr pps_idr;
+extern struct timespec pps_irq_ts[];
+
+extern struct device_attribute pps_attrs[];
+
+/*
+ * Exported functions
+ */
+
+struct pps_device *pps_get_source(int source);
+extern void pps_put_source(struct pps_device *pps);
+extern int pps_register_source(struct pps_source_info *info,
+                                int default_params);
+extern void pps_unregister_source(int source);
+extern int pps_register_cdev(struct pps_device *pps);
+extern void pps_unregister_cdev(struct pps_device *pps);
+extern void pps_event(int source, struct pps_ktime *ts, int event, void *data);