1* Freescale QorIQ 1588 timer based PTP clock
2
3General Properties:
4
5  - compatible   Should be "fsl,etsec-ptp" for eTSEC
6                 Should be "fsl,fman-ptp-timer" for DPAA FMan
7                 Should be "fsl,dpaa2-ptp" for DPAA2
8                 Should be "fsl,enetc-ptp" for ENETC
9  - reg          Offset and length of the register set for the device
10  - interrupts   There should be at least two interrupts. Some devices
11                 have as many as four PTP related interrupts.
12
13Clock Properties:
14
15  - fsl,cksel        Timer reference clock source.
16  - fsl,tclk-period  Timer reference clock period in nanoseconds.
17  - fsl,tmr-prsc     Prescaler, divides the output clock.
18  - fsl,tmr-add      Frequency compensation value.
19  - fsl,tmr-fiper1   Fixed interval period pulse generator.
20  - fsl,tmr-fiper2   Fixed interval period pulse generator.
21  - fsl,max-adj      Maximum frequency adjustment in parts per billion.
22  - fsl,extts-fifo   The presence of this property indicates hardware
23		     support for the external trigger stamp FIFO.
24  - little-endian    The presence of this property indicates the 1588 timer
25		     IP block is little-endian mode. The default endian mode
26		     is big-endian.
27
28  These properties set the operational parameters for the PTP
29  clock. You must choose these carefully for the clock to work right.
30  Here is how to figure good values:
31
32  TimerOsc     = selected reference clock   MHz
33  tclk_period  = desired clock period       nanoseconds
34  NominalFreq  = 1000 / tclk_period         MHz
35  FreqDivRatio = TimerOsc / NominalFreq     (must be greater that 1.0)
36  tmr_add      = ceil(2^32 / FreqDivRatio)
37  OutputClock  = NominalFreq / tmr_prsc     MHz
38  PulseWidth   = 1 / OutputClock            microseconds
39  FiperFreq1   = desired frequency in Hz
40  FiperDiv1    = 1000000 * OutputClock / FiperFreq1
41  tmr_fiper1   = tmr_prsc * tclk_period * FiperDiv1 - tclk_period
42  max_adj      = 1000000000 * (FreqDivRatio - 1.0) - 1
43
44  The calculation for tmr_fiper2 is the same as for tmr_fiper1. The
45  driver expects that tmr_fiper1 will be correctly set to produce a 1
46  Pulse Per Second (PPS) signal, since this will be offered to the PPS
47  subsystem to synchronize the Linux clock.
48
49  Reference clock source is determined by the value, which is holded
50  in CKSEL bits in TMR_CTRL register. "fsl,cksel" property keeps the
51  value, which will be directly written in those bits, that is why,
52  according to reference manual, the next clock sources can be used:
53
54  For eTSEC,
55  <0> - external high precision timer reference clock (TSEC_TMR_CLK
56        input is used for this purpose);
57  <1> - eTSEC system clock;
58  <2> - eTSEC1 transmit clock;
59  <3> - RTC clock input.
60
61  For DPAA FMan,
62  <0> - external high precision timer reference clock (TMR_1588_CLK)
63  <1> - MAC system clock (1/2 FMan clock)
64  <2> - reserved
65  <3> - RTC clock oscillator
66
67  When this attribute is not used, the IEEE 1588 timer reference clock
68  will use the eTSEC system clock (for Gianfar) or the MAC system
69  clock (for DPAA).
70
71Example:
72
73	ptp_clock@24e00 {
74		compatible = "fsl,etsec-ptp";
75		reg = <0x24E00 0xB0>;
76		interrupts = <12 0x8 13 0x8>;
77		interrupt-parent = < &ipic >;
78		fsl,cksel       = <1>;
79		fsl,tclk-period = <10>;
80		fsl,tmr-prsc    = <100>;
81		fsl,tmr-add     = <0x999999A4>;
82		fsl,tmr-fiper1  = <0x3B9AC9F6>;
83		fsl,tmr-fiper2  = <0x00018696>;
84		fsl,max-adj     = <659999998>;
85	};
86