- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
hello,
i ve some problem with the network performance and the cyclone 5 on linux. i try different kernel versions, after some error research i found the solution, it was/is the ethernet skew. with the socfpga default device tree source @github (socfpga_cyclone5_sockit.dts), i get only ~10-40 Mbits/s with iperf. i change the skew at the dts and the speed is now ~600Mbits/s. That was the original stuff:&gmac1 {
status = "okay";
phy-mode = "rgmii";
rxd0-skew-ps = <0>;
rxd1-skew-ps = <0>;
rxd2-skew-ps = <0>;
rxd3-skew-ps = <0>;
txen-skew-ps = <0>;
txc-skew-ps = <2600>;
rxdv-skew-ps = <0>;
rxc-skew-ps = <2000>;
};
i change it to: &gmac1 {
status = "okay";
phy-mode = "rgmii";
txd0-skew-ps = <0>; /* -420ps */
txd1-skew-ps = <0>; /* -420ps */
txd2-skew-ps = <0>; /* -420ps */
txd3-skew-ps = <0>; /* -420ps */
rxd0-skew-ps = <420>; /* 0ps */
rxd1-skew-ps = <420>; /* 0ps */
rxd2-skew-ps = <420>; /* 0ps */
rxd3-skew-ps = <420>; /* 0ps */
txen-skew-ps = <0>; /* -420ps */
txc-skew-ps = <1860>; /* 960ps */
rxdv-skew-ps = <420>; /* 0ps */
rxc-skew-ps = <1680>; /* 780ps */
max-frame-size = <3800>;
status = "okay";
};
Where can i get the skew settings? i dont want to roll the dice. we use an custom design board with cylcone 5 and an micrel ksz9031 phy. thanks for the support
Link Copied
1 Reply
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hello roll3,
I stumbled over the same question. So how to find/calculate the correct PHY skew settings? I found the following two sources which deals with the topic: 1.“Cyclone V and Arria V SoC Device Design Guideline -> Board Design Guideline for SoC FPGAs -> Design Guideline for HPS Interfaces -> HPS EMAC PHY Interface: https://www.altera.com/documentation/doq1481305867183.html#fvj1481304448658 2. KSZ9031RNX Datasheet -> 3.9.3 RGMII PAD SKEW REGISTERS: http://ww1.microchip.com/downloads/en/devicedoc/00002117f.pdf So the skew settings depends on the used MAC (here Cyclone V), the board traces (your layout) and the PHY (here the KSZ9031). However, I did not figure out how to apply the given information correctly. Do you have newer information about the topic? Best regards, niosIIuser
Reply
Topic Options
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page