1Micrel KSZ9021/KSZ9031/KSZ9131 Gigabit Ethernet PHY
2
3Some boards require special tuning values, particularly when it comes
4to clock delays. You can specify clock delay values in the PHY OF
5device node. Deprecated, but still supported, these properties can
6also be added to an Ethernet OF device node.
7
8Note that these settings are applied after any phy-specific fixup from
9phy_fixup_list (see phy_init_hw() from drivers/net/phy/phy_device.c),
10and therefore may overwrite them.
11
12KSZ9021:
13
14  All skew control options are specified in picoseconds. The minimum
15  value is 0, the maximum value is 3000, and it can be specified in 200ps
16  steps, *but* these values are in not fact what you get because this chip's
17  skew values actually increase in 120ps steps, starting from -840ps. The
18  incorrect values came from an error in the original KSZ9021 datasheet
19  before it was corrected in revision 1.2 (Feb 2014), but it is too late to
20  change the driver now because of the many existing device trees that have
21  been created using values that go up in increments of 200.
22
23  The following table shows the actual skew delay you will get for each of the
24  possible devicetree values, and the number that will be programmed into the
25  corresponding pad skew register:
26
27  Device Tree Value	Delay	Pad Skew Register Value
28  -----------------------------------------------------
29	0   		-840ps		0000
30	200 		-720ps		0001
31	400 		-600ps		0010
32	600 		-480ps		0011
33	800 		-360ps		0100
34	1000		-240ps		0101
35	1200		-120ps		0110
36	1400		   0ps		0111
37	1600		 120ps		1000
38	1800		 240ps		1001
39	2000		 360ps		1010
40	2200		 480ps		1011
41	2400		 600ps		1100
42	2600		 720ps		1101
43	2800		 840ps		1110
44	3000		 960ps		1111
45
46  Optional properties:
47
48    - rxc-skew-ps : Skew control of RXC pad
49    - rxdv-skew-ps : Skew control of RX CTL pad
50    - txc-skew-ps : Skew control of TXC pad
51    - txen-skew-ps : Skew control of TX CTL pad
52    - rxd0-skew-ps : Skew control of RX data 0 pad
53    - rxd1-skew-ps : Skew control of RX data 1 pad
54    - rxd2-skew-ps : Skew control of RX data 2 pad
55    - rxd3-skew-ps : Skew control of RX data 3 pad
56    - txd0-skew-ps : Skew control of TX data 0 pad
57    - txd1-skew-ps : Skew control of TX data 1 pad
58    - txd2-skew-ps : Skew control of TX data 2 pad
59    - txd3-skew-ps : Skew control of TX data 3 pad
60
61KSZ9031:
62
63  All skew control options are specified in picoseconds. The minimum
64  value is 0, and the maximum is property-dependent. The increment
65  step is 60ps. The default value is the neutral setting, so setting
66  rxc-skew-ps=<0> actually results in -900 picoseconds adjustment.
67
68  Optional properties:
69
70    Maximum value of 1860, default value 900:
71
72      - rxc-skew-ps : Skew control of RX clock pad
73      - txc-skew-ps : Skew control of TX clock pad
74
75    Maximum value of 900, default value 420:
76
77      - rxdv-skew-ps : Skew control of RX CTL pad
78      - txen-skew-ps : Skew control of TX CTL pad
79      - rxd0-skew-ps : Skew control of RX data 0 pad
80      - rxd1-skew-ps : Skew control of RX data 1 pad
81      - rxd2-skew-ps : Skew control of RX data 2 pad
82      - rxd3-skew-ps : Skew control of RX data 3 pad
83      - txd0-skew-ps : Skew control of TX data 0 pad
84      - txd1-skew-ps : Skew control of TX data 1 pad
85      - txd2-skew-ps : Skew control of TX data 2 pad
86      - txd3-skew-ps : Skew control of TX data 3 pad
87
88    - micrel,force-master:
89        Boolean, force phy to master mode. Only set this option if the phy
90        reference clock provided at CLK125_NDO pin is used as MAC reference
91        clock because the clock jitter in slave mode is to high (errata#2).
92        Attention: The link partner must be configurable as slave otherwise
93        no link will be established.
94
95KSZ9131:
96
97  All skew control options are specified in picoseconds. The increment
98  step is 100ps. Unlike KSZ9031, the values represent picoseccond delays.
99  A negative value can be assigned as rxc-skew-psec = <(-100)>;.
100
101  Optional properties:
102
103    Range of the value -700 to 2400, default value 0:
104
105      - rxc-skew-psec : Skew control of RX clock pad
106      - txc-skew-psec : Skew control of TX clock pad
107
108    Range of the value -700 to 800, default value 0:
109
110      - rxdv-skew-psec : Skew control of RX CTL pad
111      - txen-skew-psec : Skew control of TX CTL pad
112      - rxd0-skew-psec : Skew control of RX data 0 pad
113      - rxd1-skew-psec : Skew control of RX data 1 pad
114      - rxd2-skew-psec : Skew control of RX data 2 pad
115      - rxd3-skew-psec : Skew control of RX data 3 pad
116      - txd0-skew-psec : Skew control of TX data 0 pad
117      - txd1-skew-psec : Skew control of TX data 1 pad
118      - txd2-skew-psec : Skew control of TX data 2 pad
119      - txd3-skew-psec : Skew control of TX data 3 pad
120
121Examples:
122
123	mdio {
124		phy0: ethernet-phy@0 {
125			rxc-skew-ps = <3000>;
126			rxdv-skew-ps = <0>;
127			txc-skew-ps = <3000>;
128			txen-skew-ps = <0>;
129			reg = <0>;
130		};
131	};
132	ethernet@70000 {
133		phy = <&phy0>;
134		phy-mode = "rgmii-id";
135	};
136