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1Micrel KSZ9021/KSZ9031 Gigabit Ethernet PHY
2
3Some boards require special tuning values, particularly when it comes to
4clock delays. You can specify clock delay values by adding
5micrel-specific properties to an Ethernet OF device node.
6
7Note that these settings are applied after any phy-specific fixup from
8phy_fixup_list (see phy_init_hw() from drivers/net/phy/phy_device.c),
9and therefore may overwrite them.
10
11KSZ9021:
12
13  All skew control options are specified in picoseconds. The minimum
14  value is 0, the maximum value is 1800, and it is incremented by 120ps
15  steps.
16
17  Optional properties:
18
19    - rxc-skew-ps : Skew control of RXC pad
20    - rxdv-skew-ps : Skew control of RX CTL pad
21    - txc-skew-ps : Skew control of TXC pad
22    - txen-skew-ps : Skew control of TX CTL pad
23    - rxd0-skew-ps : Skew control of RX data 0 pad
24    - rxd1-skew-ps : Skew control of RX data 1 pad
25    - rxd2-skew-ps : Skew control of RX data 2 pad
26    - rxd3-skew-ps : Skew control of RX data 3 pad
27    - txd0-skew-ps : Skew control of TX data 0 pad
28    - txd1-skew-ps : Skew control of TX data 1 pad
29    - txd2-skew-ps : Skew control of TX data 2 pad
30    - txd3-skew-ps : Skew control of TX data 3 pad
31
32KSZ9031:
33
34  All skew control options are specified in picoseconds. The minimum
35  value is 0, and the maximum is property-dependent. The increment
36  step is 60ps.
37
38  The KSZ9031 hardware supports a range of skew values from negative to
39  positive, where the specific range is property dependent. All values
40  specified in the devicetree are offset by the minimum value so they
41  can be represented as positive integers in the devicetree since it's
42  difficult to represent a negative number in the devictree.
43
44  The following 5-bit values table apply to rxc-skew-ps and txc-skew-ps.
45
46  Pad Skew Value	Delay (ps)	Devicetree Value
47  ------------------------------------------------------
48  0_0000		-900ps		0
49  0_0001		-840ps		60
50  0_0010		-780ps		120
51  0_0011		-720ps		180
52  0_0100		-660ps		240
53  0_0101		-600ps		300
54  0_0110		-540ps		360
55  0_0111		-480ps		420
56  0_1000		-420ps		480
57  0_1001		-360ps		540
58  0_1010		-300ps		600
59  0_1011		-240ps		660
60  0_1100		-180ps		720
61  0_1101		-120ps		780
62  0_1110		-60ps		840
63  0_1111		0ps		900
64  1_0000		60ps		960
65  1_0001		120ps		1020
66  1_0010		180ps		1080
67  1_0011		240ps		1140
68  1_0100		300ps		1200
69  1_0101		360ps		1260
70  1_0110		420ps		1320
71  1_0111		480ps		1380
72  1_1000		540ps		1440
73  1_1001		600ps		1500
74  1_1010		660ps		1560
75  1_1011		720ps		1620
76  1_1100		780ps		1680
77  1_1101		840ps		1740
78  1_1110		900ps		1800
79  1_1111		960ps		1860
80
81  The following 4-bit values table apply to the txdX-skew-ps, rxdX-skew-ps
82  data pads, and the rxdv-skew-ps, txen-skew-ps control pads.
83
84  Pad Skew Value	Delay (ps)	Devicetree Value
85  ------------------------------------------------------
86  0000			-420ps		0
87  0001			-360ps		60
88  0010			-300ps		120
89  0011			-240ps		180
90  0100			-180ps		240
91  0101			-120ps		300
92  0110			-60ps		360
93  0111			0ps		420
94  1000			60ps		480
95  1001			120ps		540
96  1010			180ps		600
97  1011			240ps		660
98  1100			300ps		720
99  1101			360ps		780
100  1110			420ps		840
101  1111			480ps		900
102
103  Optional properties:
104
105    Maximum value of 1860:
106
107      - rxc-skew-ps : Skew control of RX clock pad
108      - txc-skew-ps : Skew control of TX clock pad
109
110    Maximum value of 900:
111
112      - rxdv-skew-ps : Skew control of RX CTL pad
113      - txen-skew-ps : Skew control of TX CTL pad
114      - rxd0-skew-ps : Skew control of RX data 0 pad
115      - rxd1-skew-ps : Skew control of RX data 1 pad
116      - rxd2-skew-ps : Skew control of RX data 2 pad
117      - rxd3-skew-ps : Skew control of RX data 3 pad
118      - txd0-skew-ps : Skew control of TX data 0 pad
119      - txd1-skew-ps : Skew control of TX data 1 pad
120      - txd2-skew-ps : Skew control of TX data 2 pad
121      - txd3-skew-ps : Skew control of TX data 3 pad
122
123Examples:
124
125	/* Attach to an Ethernet device with autodetected PHY */
126	&enet {
127		rxc-skew-ps = <1800>;
128		rxdv-skew-ps = <0>;
129		txc-skew-ps = <1800>;
130		txen-skew-ps = <0>;
131		status = "okay";
132	};
133
134	/* Attach to an explicitly-specified PHY */
135	mdio {
136		phy0: ethernet-phy@0 {
137			rxc-skew-ps = <1800>;
138			rxdv-skew-ps = <0>;
139			txc-skew-ps = <1800>;
140			txen-skew-ps = <0>;
141			reg = <0>;
142		};
143	};
144	ethernet@70000 {
145		status = "okay";
146		phy = <&phy0>;
147		phy-mode = "rgmii-id";
148	};
149
150References
151
152  Micrel ksz9021rl/rn Data Sheet, Revision 1.2. Dated 2/13/2014.
153  http://www.micrel.com/_PDF/Ethernet/datasheets/ksz9021rl-rn_ds.pdf
154
155  Micrel ksz9031rnx Data Sheet, Revision 2.1. Dated 11/20/2014.
156  http://www.micrel.com/_PDF/Ethernet/datasheets/KSZ9031RNX.pdf
157
158Notes:
159
160  Note that a previous version of the Micrel ksz9021rl/rn Data Sheet
161  was missing extended register 106 (transmit data pad skews), and
162  incorrectly specified the ps per step as 200ps/step instead of
163  120ps/step. The latest update to this document reflects the latest
164  revision of the Micrel specification even though usage in the kernel
165  still reflects that incorrect document.
166