From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rabeeh Khoury Date: Mon, 04 May 2015 15:35:08 +0300 Subject: [U-Boot] [PATCH 1/2] mx6cuboxi: Fix Ethernet PHY detection problem In-Reply-To: <5546F32B.4020600@mail.bg> References: <1430710213-28008-1-git-send-email-festevam@gmail.com> <5546F32B.4020600@mail.bg> Message-ID: <5547677C.4020604@solid-run.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 05/04/2015 07:18 AM, Nikolay Dimitrov wrote: > Hi Fabio, > > On 05/04/2015 06:30 AM, Fabio Estevam wrote: >> From: Fabio Estevam >> >> mx6cuboxi sometimes fails to recognize the Ethernet PHY: >> >> Net: Phy 0 not found >> >> The explanation comes from a patch from Rabeeh: >> >> "The LED_ACT pin on the carrier-one boards had a pull down that >> forces the phy address to 0x0; where on CuBox-i and the production >> HummingBoard that pin is connected directly to LED that depending on >> the pull down strength of the LED it might be sampled as '0' or '1' >> thus the phy address might appear as either address 0x0 or 0x4." > > There's no such thing as "LED pull-down". The forward voltage drop of a > LED is between 1.65V (red low-power LEDs) to 2.1V (green LEDs) to even > more for blue LEDs. Even the lowest Vf doesn't qualify as logic "0" for > LVCMOS33, which is around 1V max (Vil). The LED just can't pull-down the > voltage level low enough. This is AR8035 implementation; in reset stage the LED pin is configured as input, and pull up/down does matter. In this case it configures the PHY address. After reset is deasserted the same LED pin becomes output and then according to the previous pull/up it should be active high/low (i.e. driver or sink).