This patch adds an infrastructure for hardware clocks that implement
IEEE 1588, the Precision Time Protocol (PTP). A class driver offers a
registration method to particular hardware clock drivers. Each clock is
exposed to user space as a character device with ioctls that allow tuning
of the PTP clock.
Signed-off-by: Richard Cochran richard.coch...@omicron.at
---
Documentation/ptp/ptp.txt| 95 +++
Documentation/ptp/testptp.c | 245 ++
Documentation/ptp/testptp.mk | 33 +++
drivers/Kconfig |2 +
drivers/Makefile |1 +
drivers/ptp/Kconfig | 26 ++
drivers/ptp/Makefile |5 +
drivers/ptp/ptp_clock.c | 512 ++
include/linux/Kbuild |1 +
include/linux/ptp_clock.h| 79 ++
include/linux/ptp_clock_kernel.h | 137 ++
11 files changed, 1136 insertions(+), 0 deletions(-)
create mode 100644 Documentation/ptp/ptp.txt
create mode 100644 Documentation/ptp/testptp.c
create mode 100644 Documentation/ptp/testptp.mk
create mode 100644 drivers/ptp/Kconfig
create mode 100644 drivers/ptp/Makefile
create mode 100644 drivers/ptp/ptp_clock.c
create mode 100644 include/linux/ptp_clock.h
create mode 100644 include/linux/ptp_clock_kernel.h
diff --git a/Documentation/ptp/ptp.txt b/Documentation/ptp/ptp.txt
new file mode 100644
index 000..46858b3
--- /dev/null
+++ b/Documentation/ptp/ptp.txt
@@ -0,0 +1,95 @@
+
+* PTP infrastructure for Linux
+
+ This patch set introduces support for IEEE 1588 PTP clocks in
+ Linux. Together with the SO_TIMESTAMPING socket options, this
+ presents a standardized method for developing PTP user space
+ programs, synchronizing Linux with external clocks, and using the
+ ancillary features of PTP hardware clocks.
+
+ A new class driver exports a kernel interface for specific clock
+ drivers and a user space interface. The infrastructure supports a
+ complete set of PTP functionality.
+
+ + Basic clock operations
+- Set time
+- Get time
+- Shift the clock by a given offset atomically
+- Adjust clock frequency
+
+ + Ancillary clock features
+- One short or periodic alarms, with signal delivery to user program
+- Time stamp external events
+- Period output signals configurable from user space
+- Synchronization of the Linux system time via the PPS subsystem
+
+** PTP kernel API
+
+ A PTP clock driver registers itself with the class driver. The
+ class driver handles all of the dealings with user space. The
+ author of a clock driver need only implement the details of
+ programming the clock hardware. The clock driver notifies the class
+ driver of asynchronous events (alarms and external time stamps) via
+ a simple message passing interface.
+
+ The class driver supports multiple PTP clock drivers. In normal use
+ cases, only one PTP clock is needed. However, for testing and
+ development, it can be useful to have more than one clock in a
+ single system, in order to allow performance comparisons.
+
+** PTP user space API
+
+ The class driver creates a character device for each registered PTP
+ clock. User space programs may control the clock using standardized
+ ioctls. A program may query, enable, configure, and disable the
+ ancillary clock features. User space can receive time stamped
+ events via blocking read() and poll(). One shot and periodic
+ signals may be configured via an ioctl API with semantics similar
+ to the POSIX timer_settime() system call.
+
+ As an real life example, the following two patches for ptpd version
+ 1.0.0 demonstrate how the API works.
+
+
https://sourceforge.net/tracker/?func=detailaid=2992845group_id=139814atid=744634
+
+
https://sourceforge.net/tracker/?func=detailaid=2992847group_id=139814atid=744634
+
+** Writing clock drivers
+
+ Clock drivers include include/linux/ptp_clock_kernel.h and register
+ themselves by presenting a 'struct ptp_clock_info' to the
+ registration method. Clock drivers must implement all of the
+ functions in the interface. If a clock does not offer a particular
+ ancillary feature, then the driver should just return -EOPNOTSUPP
+ from those functions.
+
+ Drivers must ensure that all of the methods in interface are
+ reentrant. Since most hardware implementations treat the time value
+ as a 64 bit integer accessed as two 32 bit registers, drivers
+ should use spin_lock_irqsave/spin_unlock_irqrestore to protect
+ against concurrent access. This locking cannot be accomplished in
+ class driver, since the lock may also be needed by the clock
+ driver's interrupt service routine.
+
+** Supported hardware
+
+ + Standard Linux system timer
+ - No special PTP features
+ - For use with software time stamping
+
+ + Freescale eTSEC gianfar
+ - 2 Time stamp external triggers, programmable polarity (opt. interrupt)
+ - 2
