Micrel KSZ9031 var-som-mx6 1GBps issue

[ameerhamza]

Hi all,

Its me again. I was developing ethernet driver for custom OS, so i am not using Linux. 100 MBps connection works fine but if we switch to 1000 MBps the data transmit through the line gets corrupted, however Auto-Negotiation successfully occurs and both the link partners switch to 1GBps connection but data transmission is not right. I am using 125-MHz clock (ENET_PLL-> div = 3) and setting SPEED bit in ECR_REGISTER to 1 for 1GBPs. I also set RGMII_CLOCK_SKEW to 0x3ff (as mentioned in U-Boot), if i leave clock skew register to it default value, no data transmit through the line. If i set it to 0x3ff data corruption is observed. I also set RX_SKEW to 0 and CONTROL_SKEW to 0 but still not help. Also went through micrel.c and net/FEC linux driver but still no luck. If any one plz could suggest if I am missing anything would be really helpful. Looking forward for you kind respnse.

Thanks,
Hamza.

[chenw]

how about now，please

[igorpadykov]

Hi Hamza

it may be useful to check timings with oscilloscope

given in sect.4.11.5.3 RGMII Signal Switching Specifications

i.MX6DQ Datasheet

http://cache.freescale.com/files/32bit/doc/data_sheet/IMX6DQCEC.pdf

Best regards
igor
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[ameerhamza]

Hi Igor,

Your quick response is always appreciated. Unfortunately I don't have oscilloscope available with me, but after hacking code from u-boot I hope that my current PAD settings are good, please correct me if I am wrong:

RX Data Pad Skew = 0x0;

TX Data Pad Skew = 0x0;

Control Signal Pad Skew = 0x0;

Clock Pad Skew = 0x3ff;

Attached manual also says that DDR_SEL should be 0b11 and DSE should be 0b111, why we need to increase the voltage ? Although I tried it also but still can not transmit packets successfully.

I am also using CCM_ANALOG_PLL_ENET->divider = 3 which I am assuming that the clock would be 125 MHz. Also MII Speed divider I am using is 24 which should feed PHY clock of 2.5 MHz.

For clearing my problem a little more to you, I sent same DHCP Discover packet for both 100 Mbps and 1000 Mbps modes. 100 Mbps behavior was correct and packet looked like this on wireshark.

But when I transmit the same packet for 1000 Mbps the packet got corrupted and I got following log:

Since I don't have oscilloscope available with me it would be very nice of you to verify my skew values. also by looking at both the packets what you think can be a problem. Please ask me if I need to provide you more details. Yous help would be really highly appreciated :smileyhappy:

Thanks,

Hamza.