From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikolay Dimitrov Date: Mon, 04 May 2015 17:06:09 +0300 Subject: [U-Boot] [PATCH 1/2] mx6cuboxi: Fix Ethernet PHY detection problem In-Reply-To: References: <1430710213-28008-1-git-send-email-festevam@gmail.com> <5546F32B.4020600@mail.bg> Message-ID: <55477CD1.6050209@mail.bg> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Fabio, On 05/04/2015 03:22 PM, Fabio Estevam wrote: > Hi Nikolay, > > On Mon, May 4, 2015 at 1:18 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. >> >> So, unless you have some control over the pin (via a programmable >> on-chip pull-up or pull-down) which I doubt as it's a PHY pin, the >> actual behavior is that the pin is floating, and samples a random >> value at boot. Which means, the hardware is just buggy. > > As mentioned in the commit log this explanation comes from > Solid-run. > > The key point here is that the PHY can appear at 0x0 and 0x4, so this > patch handles such case. Yes, I saw that. Sorry for the off-topic. The reason I allowed myself to comment is that this text will go into git log, and people can treat it as the proper way to configure boot-strapable pins, which I don't think it is. Otherwise your patch is completely OK - this is the only way to fix such behavior of the hardware. Kind regards, Nikolay