Documentation/devicetree/bindings/net/micrel-ksz90x1.txt

   1 Micrel KSZ9021/KSZ9031/KSZ9131 Gigabit Ethernet PHY
   2
   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.
   7
   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.
  11
  12 KSZ9021:
  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
  61 KSZ9031:
  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   The KSZ9031 hardware supports a range of skew values from negative to
  69   positive, where the specific range is property dependent. All values
  70   specified in the devicetree are offset by the minimum value so they
  71   can be represented as positive integers in the devicetree since it's
  72   difficult to represent a negative number in the devictree.
  73
  74   The following 5-bit values table apply to rxc-skew-ps and txc-skew-ps.
  75
  76   Pad Skew Value        Delay (ps)      Devicetree Value
  77   ------------------------------------------------------
  78   0_0000                -900ps          0
  79   0_0001                -840ps          60
  80   0_0010                -780ps          120
  81   0_0011                -720ps          180
  82   0_0100                -660ps          240
  83   0_0101                -600ps          300
  84   0_0110                -540ps          360
  85   0_0111                -480ps          420
  86   0_1000                -420ps          480
  87   0_1001                -360ps          540
  88   0_1010                -300ps          600
  89   0_1011                -240ps          660
  90   0_1100                -180ps          720
  91   0_1101                -120ps          780
  92   0_1110                -60ps           840
  93   0_1111                0ps             900
  94   1_0000                60ps            960
  95   1_0001                120ps           1020
  96   1_0010                180ps           1080
  97   1_0011                240ps           1140
  98   1_0100                300ps           1200
  99   1_0101                360ps           1260
 100   1_0110                420ps           1320
 101   1_0111                480ps           1380
 102   1_1000                540ps           1440
 103   1_1001                600ps           1500
 104   1_1010                660ps           1560
 105   1_1011                720ps           1620
 106   1_1100                780ps           1680
 107   1_1101                840ps           1740
 108   1_1110                900ps           1800
 109   1_1111                960ps           1860
 110
 111   The following 4-bit values table apply to the txdX-skew-ps, rxdX-skew-ps
 112   data pads, and the rxdv-skew-ps, txen-skew-ps control pads.
 113
 114   Pad Skew Value        Delay (ps)      Devicetree Value
 115   ------------------------------------------------------
 116   0000                  -420ps          0
 117   0001                  -360ps          60
 118   0010                  -300ps          120
 119   0011                  -240ps          180
 120   0100                  -180ps          240
 121   0101                  -120ps          300
 122   0110                  -60ps           360
 123   0111                  0ps             420
 124   1000                  60ps            480
 125   1001                  120ps           540
 126   1010                  180ps           600
 127   1011                  240ps           660
 128   1100                  300ps           720
 129   1101                  360ps           780
 130   1110                  420ps           840
 131   1111                  480ps           900
 132
 133   Optional properties:
 134
 135     Maximum value of 1860, default value 900:
 136
 137       - rxc-skew-ps : Skew control of RX clock pad
 138       - txc-skew-ps : Skew control of TX clock pad
 139
 140     Maximum value of 900, default value 420:
 141
 142       - rxdv-skew-ps : Skew control of RX CTL pad
 143       - txen-skew-ps : Skew control of TX CTL pad
 144       - rxd0-skew-ps : Skew control of RX data 0 pad
 145       - rxd1-skew-ps : Skew control of RX data 1 pad
 146       - rxd2-skew-ps : Skew control of RX data 2 pad
 147       - rxd3-skew-ps : Skew control of RX data 3 pad
 148       - txd0-skew-ps : Skew control of TX data 0 pad
 149       - txd1-skew-ps : Skew control of TX data 1 pad
 150       - txd2-skew-ps : Skew control of TX data 2 pad
 151       - txd3-skew-ps : Skew control of TX data 3 pad
 152
 153     - micrel,force-master:
 154         Boolean, force phy to master mode. Only set this option if the phy
 155         reference clock provided at CLK125_NDO pin is used as MAC reference
 156         clock because the clock jitter in slave mode is to high (errata#2).
 157         Attention: The link partner must be configurable as slave otherwise
 158         no link will be established.
 159
 160 KSZ9131:
 161
 162   All skew control options are specified in picoseconds. The increment
 163   step is 100ps. Unlike KSZ9031, the values represent picoseccond delays.
 164   A negative value can be assigned as rxc-skew-psec = <(-100)>;.
 165
 166   Optional properties:
 167
 168     Range of the value -700 to 2400, default value 0:
 169
 170       - rxc-skew-psec : Skew control of RX clock pad
 171       - txc-skew-psec : Skew control of TX clock pad
 172
 173     Range of the value -700 to 800, default value 0:
 174
 175       - rxdv-skew-psec : Skew control of RX CTL pad
 176       - txen-skew-psec : Skew control of TX CTL pad
 177       - rxd0-skew-psec : Skew control of RX data 0 pad
 178       - rxd1-skew-psec : Skew control of RX data 1 pad
 179       - rxd2-skew-psec : Skew control of RX data 2 pad
 180       - rxd3-skew-psec : Skew control of RX data 3 pad
 181       - txd0-skew-psec : Skew control of TX data 0 pad
 182       - txd1-skew-psec : Skew control of TX data 1 pad
 183       - txd2-skew-psec : Skew control of TX data 2 pad
 184       - txd3-skew-psec : Skew control of TX data 3 pad
 185
 186 Examples:
 187
 188         /* Attach to an Ethernet device with autodetected PHY */
 189         &enet {
 190                 rxc-skew-ps = <1800>;
 191                 rxdv-skew-ps = <0>;
 192                 txc-skew-ps = <1800>;
 193                 txen-skew-ps = <0>;
 194                 status = "okay";
 195         };
 196
 197         /* Attach to an explicitly-specified PHY */
 198         mdio {
 199                 phy0: ethernet-phy@0 {
 200                         rxc-skew-ps = <1800>;
 201                         rxdv-skew-ps = <0>;
 202                         txc-skew-ps = <1800>;
 203                         txen-skew-ps = <0>;
 204                         reg = <0>;
 205                 };
 206         };
 207         ethernet@70000 {
 208                 phy = <&phy0>;
 209                 phy-mode = "rgmii-id";
 210         };
 211
 212 References
 213
 214   Micrel ksz9021rl/rn Data Sheet, Revision 1.2. Dated 2/13/2014.
 215   http://www.micrel.com/_PDF/Ethernet/datasheets/ksz9021rl-rn_ds.pdf
 216
 217   Micrel ksz9031rnx Data Sheet, Revision 2.1. Dated 11/20/2014.
 218   http://www.micrel.com/_PDF/Ethernet/datasheets/KSZ9031RNX.pdf
 219
 220 Notes:
 221
 222   Note that a previous version of the Micrel ksz9021rl/rn Data Sheet
 223   was missing extended register 106 (transmit data pad skews), and
 224   incorrectly specified the ps per step as 200ps/step instead of
 225   120ps/step. The latest update to this document reflects the latest
 226   revision of the Micrel specification even though usage in the kernel
 227   still reflects that incorrect document.