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Commitff7bd212cb("net: phy: micrel: fix divisor value for KSZ9031 phy skew") fixed the skew value divisor for the KSZ9031, but left the code using the same divisor for the KSZ9021, which is incorrect. The preceding commitc16e69f702("net: phy: micrel: add documentation for Micrel KSZ90x1 binding") added the DTS documentation for the KSZ90x1, changing it from the equivalent file in the Linux kernel to correctly state that for this part the skew value is set in 120ps steps, whereas the Linux documentation and driver continue to this day to use the incorrect value of 200 that came from the original KSZ9021 datasheet before it was corrected in revision 1.2 (Feb 2014). This commit sorts out the resulting confusion in a consistent way by making the following changes: - Update the documentation to be clear about what the skew values mean, in the same was as for the KSZ9031. - Update the Micrel PHY driver to select the appropriate divisor for both parts. - Adjust all the device trees that state skew values for KSZ9021 PHYs to use values based on 120ps steps instead of 200ps steps. This will result in the same values being programmed into the skew registers as the equivalent device trees in the Linux kernel do, where it incorrectly uses 200ps steps (since that's where all these device trees were copied from). Signed-off-by: James Byrne <james.byrne@origamienergy.com> Acked-by: Joe Hershberger <joe.hershberger@ni.com>
192 lines
5.7 KiB
Text
192 lines
5.7 KiB
Text
Micrel KSZ9021/KSZ9031 Gigabit Ethernet PHY
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Some boards require special tuning values, particularly when it comes to
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clock delays. You can specify clock delay values by adding
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micrel-specific properties to an Ethernet OF device node.
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Note that these settings are applied after any phy-specific fixup from
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phy_fixup_list (see phy_init_hw() from drivers/net/phy/phy_device.c),
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and therefore may overwrite them.
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KSZ9021:
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All skew control options are specified in picoseconds. The minimum
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value is 0, the maximum value is 1800, and it is incremented by 120ps
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steps.
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The KSZ9021 hardware supports a range of skew values from negative to
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positive, where the specific range is property dependent. All values
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specified in the devicetree are offset by the minimum value so they
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can be represented as positive integers in the devicetree since it's
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difficult to represent a negative number in the devictree.
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The following 4-bit values table applies to all the skew properties:
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Pad Skew Value Delay (ps) Devicetree Value
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------------------------------------------------------
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0000 -840ps 0
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0001 -720ps 120
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0010 -600ps 240
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0011 -480ps 360
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0100 -360ps 480
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0101 -240ps 600
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0110 -120ps 720
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0111 0ps 840
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1000 120ps 960
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1001 240ps 1080
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1010 360ps 1200
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1011 480ps 1320
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1100 600ps 1440
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1101 720ps 1560
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1110 840ps 1680
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1111 960ps 1800
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Optional properties:
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- rxc-skew-ps : Skew control of RXC pad
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- rxdv-skew-ps : Skew control of RX CTL pad
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- txc-skew-ps : Skew control of TXC pad
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- txen-skew-ps : Skew control of TX CTL pad
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- rxd0-skew-ps : Skew control of RX data 0 pad
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- rxd1-skew-ps : Skew control of RX data 1 pad
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- rxd2-skew-ps : Skew control of RX data 2 pad
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- rxd3-skew-ps : Skew control of RX data 3 pad
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- txd0-skew-ps : Skew control of TX data 0 pad
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- txd1-skew-ps : Skew control of TX data 1 pad
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- txd2-skew-ps : Skew control of TX data 2 pad
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- txd3-skew-ps : Skew control of TX data 3 pad
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KSZ9031:
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All skew control options are specified in picoseconds. The minimum
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value is 0, and the maximum is property-dependent. The increment
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step is 60ps.
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The KSZ9031 hardware supports a range of skew values from negative to
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positive, where the specific range is property dependent. All values
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specified in the devicetree are offset by the minimum value so they
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can be represented as positive integers in the devicetree since it's
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difficult to represent a negative number in the devictree.
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The following 5-bit values table apply to rxc-skew-ps and txc-skew-ps.
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Pad Skew Value Delay (ps) Devicetree Value
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------------------------------------------------------
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0_0000 -900ps 0
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0_0001 -840ps 60
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0_0010 -780ps 120
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0_0011 -720ps 180
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0_0100 -660ps 240
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0_0101 -600ps 300
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0_0110 -540ps 360
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0_0111 -480ps 420
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0_1000 -420ps 480
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0_1001 -360ps 540
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0_1010 -300ps 600
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0_1011 -240ps 660
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0_1100 -180ps 720
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0_1101 -120ps 780
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0_1110 -60ps 840
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0_1111 0ps 900
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1_0000 60ps 960
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1_0001 120ps 1020
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1_0010 180ps 1080
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1_0011 240ps 1140
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1_0100 300ps 1200
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1_0101 360ps 1260
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1_0110 420ps 1320
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1_0111 480ps 1380
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1_1000 540ps 1440
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1_1001 600ps 1500
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1_1010 660ps 1560
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1_1011 720ps 1620
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1_1100 780ps 1680
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1_1101 840ps 1740
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1_1110 900ps 1800
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1_1111 960ps 1860
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The following 4-bit values table apply to the txdX-skew-ps, rxdX-skew-ps
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data pads, and the rxdv-skew-ps, txen-skew-ps control pads.
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Pad Skew Value Delay (ps) Devicetree Value
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------------------------------------------------------
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0000 -420ps 0
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0001 -360ps 60
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0010 -300ps 120
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0011 -240ps 180
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0100 -180ps 240
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0101 -120ps 300
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0110 -60ps 360
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0111 0ps 420
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1000 60ps 480
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1001 120ps 540
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1010 180ps 600
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1011 240ps 660
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1100 300ps 720
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1101 360ps 780
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1110 420ps 840
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1111 480ps 900
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Optional properties:
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Maximum value of 1860:
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- rxc-skew-ps : Skew control of RX clock pad
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- txc-skew-ps : Skew control of TX clock pad
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Maximum value of 900:
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- rxdv-skew-ps : Skew control of RX CTL pad
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- txen-skew-ps : Skew control of TX CTL pad
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- rxd0-skew-ps : Skew control of RX data 0 pad
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- rxd1-skew-ps : Skew control of RX data 1 pad
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- rxd2-skew-ps : Skew control of RX data 2 pad
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- rxd3-skew-ps : Skew control of RX data 3 pad
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- txd0-skew-ps : Skew control of TX data 0 pad
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- txd1-skew-ps : Skew control of TX data 1 pad
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- txd2-skew-ps : Skew control of TX data 2 pad
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- txd3-skew-ps : Skew control of TX data 3 pad
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Examples:
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/* Attach to an Ethernet device with autodetected PHY */
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&enet {
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rxc-skew-ps = <1800>;
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rxdv-skew-ps = <0>;
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txc-skew-ps = <1800>;
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txen-skew-ps = <0>;
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status = "okay";
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};
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/* Attach to an explicitly-specified PHY */
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mdio {
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phy0: ethernet-phy@0 {
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rxc-skew-ps = <1800>;
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rxdv-skew-ps = <0>;
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txc-skew-ps = <1800>;
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txen-skew-ps = <0>;
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reg = <0>;
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};
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};
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ethernet@70000 {
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status = "okay";
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phy = <&phy0>;
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phy-mode = "rgmii-id";
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};
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References
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Micrel ksz9021rl/rn Data Sheet, Revision 1.2. Dated 2/13/2014.
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http://www.micrel.com/_PDF/Ethernet/datasheets/ksz9021rl-rn_ds.pdf
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Micrel ksz9031rnx Data Sheet, Revision 2.1. Dated 11/20/2014.
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http://www.micrel.com/_PDF/Ethernet/datasheets/KSZ9031RNX.pdf
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Notes:
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Note that a previous version of the Micrel ksz9021rl/rn Data Sheet
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was missing extended register 106 (transmit data pad skews), and
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incorrectly specified the ps per step as 200ps/step instead of
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120ps/step. The latest update to this document reflects the latest
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revision of the Micrel specification even though usage in the kernel
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still reflects that incorrect document.
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