From: Brian Lilly <[email protected]> Data: Thursday, May 08, 2014 3:52 AM
>To: Florian Fainelli >Cc: Uwe Kleine-König; David S. Miller; Estevam Fabio-R49496; Jim Baxter; Li >Frank- >B20596; Duan Fugang-B38611; netdev; [email protected]; kernel >Subject: Re: i.MX28 based system losing eth0 on boot > >Florian: > >Thank you for your help. > >After doubling the timeout length it worked. > >I managed to get my hands on a imx28evk board and compared our component load >versus theirs, to find they have a 1.5k pull-up on ENET_MDIO to +3.3v which >wasn't >present on our board. Adding a 1.5k pull-up resistor on ENET_MDIO solves the >problem, and boots as expected without patching anything. > >Sorry for the trouble on this. > >Apparently our EE had some question as to whether or not the pull-up was >necessary, >and put it in the schematic, and the footprint on the board, but marked it as a >DNP, which of course left it off the board and out of the BOM. [...] Yes, 1.5K pull-up on MDIO is necessary, otherwise write/read phy register data is not right due to the drive strength is not enough. Thanks, Andy
