1 Micrel KSZ9021/KSZ9031/KSZ9131 Gigabit Ethernet PHY
3 Some boards require special tuning values, particularly when it comes
4 to clock delays. You can specify clock delay values in the PHY OF
5 device node. Deprecated, but still supported, these properties can
6 also be added to an Ethernet OF device node.
8 Note that these settings are applied after any phy-specific fixup from
9 phy_fixup_list (see phy_init_hw() from drivers/net/phy/phy_device.c),
10 and therefore may overwrite them.
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.
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:
27 Device Tree Value Delay Pad Skew Register Value
28 -----------------------------------------------------
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
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.
70 Maximum value of 1860, default value 900:
72 - rxc-skew-ps : Skew control of RX clock pad
73 - txc-skew-ps : Skew control of TX clock pad
75 Maximum value of 900, default value 420:
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
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.
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)>;.
103 Range of the value -700 to 2400, default value 0:
105 - rxc-skew-psec : Skew control of RX clock pad
106 - txc-skew-psec : Skew control of TX clock pad
108 Range of the value -700 to 800, default value 0:
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
124 phy0: ethernet-phy@0 {
125 rxc-skew-ps = <3000>;
127 txc-skew-ps = <3000>;
134 phy-mode = "rgmii-id";