From: Igor Plyatov <plya...@gmail.com> Sent: Monday, July 27, 2015 10:51 PM > To: linux-ker...@vger.kernel.org; netdev@vger.kernel.org > Cc: Florian Fainelli; Joe Perches; Zhou Luwei-B45643; Duan Fugang-B38611; > Richard Cochran; David S. Miller; Uwe Kleine-König; Estevam Fabio-R49496; > Lothar Waßmann; Li Frank-B20596 > Subject: Buggy cable detection on i.MX51, fec driver and LAN8700 PHY > > Dear all, > > very often we observe issue with Ethernet cable detection during cable > unplugging and plugging. > > We use Voipac i.MX51 SOMs (System On Modules). They are based on > Freescale i.MX51 CPU with LAN7800 PHY in MII mode. The schematic of PHY > connection is very similar to the Freescale i.MX51 Babbage board. > > The Ethernet interface eth0 is configured statically for simplicity, but > same issue exists with DHCP configuration. > > I did a lot of tests to determine stability of Ethernet cable detection > by the "fec" Ethernet driver. > > In normal operation, if I unplug the Ethernet cable, then "fec" driver > prints "fec 83fec000.ethernet eth0: Link is Down" and green LED (Ethernet > medium detected) is OFF. > If I plug cable back, then "fec" driver print "fec 83fec000.ethernet > eth0: Link is Up - 100Mbps/Full - flow control off" and green LED is ON. > > But sometimes, after cable plugging, "fec" driver does not print anything > on the console and green LED does not show detection of Ethernet cable. > Frequency of issue appearing is a random value. > Sometimes issue appears after second cable unplugging/plugging, but > sometimes - after 10-20 unplugging/plugging. > > The issue was tested and exists on kernels from linux-3.8.5 till current > linux-4.2-rc4-cbfe8fa6cd672011c755c3cd85c9ffd4e2d10a6f. > > Same tests was made with different versions of the Barebox bootloader and > cable detection works flawless. > > Please, help to resolve issue with Linux drivers. > > Best wishes. > -- > Igor Plyatov
For phy cable detection issue, mostly it is phy device issue like: - Phy is not stable, maybe the phy initial setting is not right. - MDIO bus read is not right, maybe MDIO/MDC pin drive strength (timing) doesn't match spec requirement. You can measure the MDIO timing firstly, and then check the phy setting. Regards, Andy
