micrel-ksz90x1.txt

  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 no way 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  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 too high (errata#2).
157        Attention: The link partner must be configurable as slave otherwise
158        no link will be established.
159
160KSZ9131:
161LAN8841:
162
163  All skew control options are specified in picoseconds. The increment
164  step is 100ps. Unlike KSZ9031, the values represent picoseccond delays.
165  A negative value can be assigned as rxc-skew-psec = <(-100)>;.
166
167  Optional properties:
168
169    Range of the value -700 to 2400, default value 0:
170
171      - rxc-skew-psec : Skew control of RX clock pad
172      - txc-skew-psec : Skew control of TX clock pad
173
174    Range of the value -700 to 800, default value 0:
175
176      - rxdv-skew-psec : Skew control of RX CTL pad
177      - txen-skew-psec : Skew control of TX CTL pad
178      - rxd0-skew-psec : Skew control of RX data 0 pad
179      - rxd1-skew-psec : Skew control of RX data 1 pad
180      - rxd2-skew-psec : Skew control of RX data 2 pad
181      - rxd3-skew-psec : Skew control of RX data 3 pad
182      - txd0-skew-psec : Skew control of TX data 0 pad
183      - txd1-skew-psec : Skew control of TX data 1 pad
184      - txd2-skew-psec : Skew control of TX data 2 pad
185      - txd3-skew-psec : Skew control of TX data 3 pad
186
187Examples:
188
189	/* Attach to an Ethernet device with autodetected PHY */
190	&enet {
191		rxc-skew-ps = <1800>;
192		rxdv-skew-ps = <0>;
193		txc-skew-ps = <1800>;
194		txen-skew-ps = <0>;
195		status = "okay";
196	};
197
198	/* Attach to an explicitly-specified PHY */
199	mdio {
200		phy0: ethernet-phy@0 {
201			rxc-skew-ps = <1800>;
202			rxdv-skew-ps = <0>;
203			txc-skew-ps = <1800>;
204			txen-skew-ps = <0>;
205			reg = <0>;
206		};
207	};
208	ethernet@70000 {
209		phy = <&phy0>;
210		phy-mode = "rgmii-id";
211	};
212
213References
214
215  Micrel ksz9021rl/rn Data Sheet, Revision 1.2. Dated 2/13/2014.
216  http://www.micrel.com/_PDF/Ethernet/datasheets/ksz9021rl-rn_ds.pdf
217
218  Micrel ksz9031rnx Data Sheet, Revision 2.1. Dated 11/20/2014.
219  http://www.micrel.com/_PDF/Ethernet/datasheets/KSZ9031RNX.pdf
220
221Notes:
222
223  Note that a previous version of the Micrel ksz9021rl/rn Data Sheet
224  was missing extended register 106 (transmit data pad skews), and
225  incorrectly specified the ps per step as 200ps/step instead of
226  120ps/step. The latest update to this document reflects the latest
227  revision of the Micrel specification even though usage in the kernel
228  still reflects that incorrect document.