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+* Freescale QorIQ 1588 timer based PTP clock
+
+General Properties:
+
+ - compatible Should be "fsl,etsec-ptp"
+ - reg Offset and length of the register set for the device
+ - interrupts There should be at least two interrupts. Some devices
+ have as many as four PTP related interrupts.
+
+Clock Properties:
+
+ - fsl,cksel Timer reference clock source.
+ - fsl,tclk-period Timer reference clock period in nanoseconds.
+ - fsl,tmr-prsc Prescaler, divides the output clock.
+ - fsl,tmr-add Frequency compensation value.
+ - fsl,tmr-fiper1 Fixed interval period pulse generator.
+ - fsl,tmr-fiper2 Fixed interval period pulse generator.
+ - fsl,max-adj Maximum frequency adjustment in parts per billion.
+
+ These properties set the operational parameters for the PTP
+ clock. You must choose these carefully for the clock to work right.
+ Here is how to figure good values:
+
+ TimerOsc = selected reference clock MHz
+ tclk_period = desired clock period nanoseconds
+ NominalFreq = 1000 / tclk_period MHz
+ FreqDivRatio = TimerOsc / NominalFreq (must be greater that 1.0)
+ tmr_add = ceil(2^32 / FreqDivRatio)
+ OutputClock = NominalFreq / tmr_prsc MHz
+ PulseWidth = 1 / OutputClock microseconds
+ FiperFreq1 = desired frequency in Hz
+ FiperDiv1 = 1000000 * OutputClock / FiperFreq1
+ tmr_fiper1 = tmr_prsc * tclk_period * FiperDiv1 - tclk_period
+ max_adj = 1000000000 * (FreqDivRatio - 1.0) - 1
+
+ The calculation for tmr_fiper2 is the same as for tmr_fiper1. The
+ driver expects that tmr_fiper1 will be correctly set to produce a 1
+ Pulse Per Second (PPS) signal, since this will be offered to the PPS
+ subsystem to synchronize the Linux clock.
+
+ Reference clock source is determined by the value, which is holded
+ in CKSEL bits in TMR_CTRL register. "fsl,cksel" property keeps the
+ value, which will be directly written in those bits, that is why,
+ according to reference manual, the next clock sources can be used:
+
+ <0> - external high precision timer reference clock (TSEC_TMR_CLK
+ input is used for this purpose);
+ <1> - eTSEC system clock;
+ <2> - eTSEC1 transmit clock;
+ <3> - RTC clock input.
+
+ When this attribute is not used, eTSEC system clock will serve as
+ IEEE 1588 timer reference clock.
+
+Example:
+
+ ptp_clock@24e00 {
+ compatible = "fsl,etsec-ptp";
+ reg = <0x24E00 0xB0>;
+ interrupts = <12 0x8 13 0x8>;
+ interrupt-parent = < &ipic >;
+ fsl,cksel = <1>;
+ fsl,tclk-period = <10>;
+ fsl,tmr-prsc = <100>;
+ fsl,tmr-add = <0x999999A4>;
+ fsl,tmr-fiper1 = <0x3B9AC9F6>;
+ fsl,tmr-fiper2 = <0x00018696>;
+ fsl,max-adj = <659999998>;
+ };