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Diffstat (limited to 'Documentation/ptp/ptp.txt')
| -rw-r--r-- | Documentation/ptp/ptp.txt | 86 |
1 files changed, 0 insertions, 86 deletions
diff --git a/Documentation/ptp/ptp.txt b/Documentation/ptp/ptp.txt deleted file mode 100644 index 11e904ee073f..000000000000 --- a/Documentation/ptp/ptp.txt +++ /dev/null @@ -1,86 +0,0 @@ - -* PTP hardware clock 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 hardware clock functionality. - - + Basic clock operations - - Set time - - Get time - - Shift the clock by a given offset atomically - - Adjust clock frequency - - + Ancillary clock features - - Time stamp external events - - Period output signals configurable from user space - - Synchronization of the Linux system time via the PPS subsystem - -** PTP hardware clock 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 hardware clock user space API - - The class driver also creates a character device for each - registered clock. User space can use an open file descriptor from - the character device as a POSIX clock id and may call - clock_gettime, clock_settime, and clock_adjtime. These calls - implement the basic clock operations. - - 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(). - -** 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 - - + Freescale eTSEC gianfar - - 2 Time stamp external triggers, programmable polarity (opt. interrupt) - - 2 Alarm registers (optional interrupt) - - 3 Periodic signals (optional interrupt) - - + National DP83640 - - 6 GPIOs programmable as inputs or outputs - - 6 GPIOs with dedicated functions (LED/JTAG/clock) can also be - used as general inputs or outputs - - GPIO inputs can time stamp external triggers - - GPIO outputs can produce periodic signals - - 1 interrupt pin - - + Intel IXP465 - - Auxiliary Slave/Master Mode Snapshot (optional interrupt) - - Target Time (optional interrupt) |