AMCC 440EP phy detection

Eddie Dawydiuk eddie at
Thu Apr 9 01:47:06 EST 2009


> I found the ibm_newemac driver(2.6.29) makes the assumption that the 
> bootloader has already configured the tx enable pin as it is a 
> multiplexed pin. Unfortuantley I am not using U-Boot and our minimal 
> bootloader does not do this.  After finding tx enable was never 
> asserting for Eth0 a quick user space program verified tx enable was 
> configured as a GPIO pin.

I would like to eventually submit our changes for upstream support. Based on 
this would you recommend ensuring tx enable is configured properly in the 
initialization of the ibm_newemac driver or the platform initialization?

>> On Tue, Apr 7, 2009 at 9:32 AM, Eddie Dawydiuk <eddie at> 
>> wrote:
>>> Hello,
>>> I'm working on a board based on the Yosemite AMCC 440EP eval board. I'm
>>> having some difficulty getting both network interfaces working. The 
>>> first
>>> problem I found is the ibm_newemac driver was detecting the two phys at
>>> address 0 and 1 where we have them wired for addresses 1 and 3. As a 
>>> result
>>> I hardcoded the phy-address in the dts file. I then found I was able to
>>> receive and send data on eth1(phy-address 3) without incident. 
>>> Although I
>>> found eth0 can receive data but I see no packets being 
>>> transmitted(using a
>>> packet sniffer) and I see no indication from a software standpoint of 
>>> any
>>> transmit failures. We are using Micrel KSZ8041FTL phys(RMII mode) 
>>> where the
>>> Yosemite board used Micrel KS8721BL phys.  I've reviewed the 
>>> schematic and
>>> it appears both phys are connected identically and I've seen this same
>>> failure on multiple boards. I thought the fact that the driver 
>>> detected a
>>> phy at address 0 might be a clue, but I can't make much of the clue. 
>>> So I
>>> thought I'd post this info in the hopes someone else might have run 
>>> into a
>>> similar problem or have a suggestion.
>> Phy address 0 is the broadcast address.  All phys will usually respond
>> to address 0 accesses.  Off the top of my head, It sounds like one PHY
>> is responding to addresses 0 & 1, and the other phy isn't responding
>> at all.
>> g.

Best Regards,
  Eddie Dawydiuk, Technologic Systems | voice:  (480) 837-5200
  16525 East Laser Drive 	     | fax:    (480) 837-5300
  Fountain Hills, AZ 85268            | web:

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