[U-Boot] Ethernet receive issue in PPC440

[prathika <prathika@deeopl.com>]

I am using PowerPC 440 EP.  The PHY I am using is DP83848. I have 
enabled RMII mode. I am making sure that all the registers are 
configured for this mode only, by reading back the registers.

First i tried enabling internal loopback in PowerPC by enabling the ILE 
bit in EMAC0_MR1 register. There was no issue. Then I wanted to test 
external loopback without RJ-45 cable. that is the data transmitted by 
Power PC is loop backed by the PHY. So i disabled the ILE bit and 
enabled FullDuplex FDE bit in EMAC0_MR1 register (As illustrated in the 
PowerPC User Manual). I also enabled Internal Loopback in PHY.I had no 
issues in this also. I was able to receive the looped back packets from 
the PHY.

Also to make sure that PHY has no issue, there is a built in test 
facility avaiilable in the PHY. I also enabled that bit and cleared for 
the passing of the Built In Test of the PHY.

But i never tried doing loop back with the RJ-45 cable. But when i 
cleared the loop back along the PHY path, should i also test looping 
back with the cable??

Thanks for your response.

Thanks & Regards,
Prathika R

Stefan Roese wrote:
> On Friday 10 April 2009, prathika wrote:
>> i am porting uboot in PowerPC 440.
>> i tried using the ping command.i have connected my board to PC via cross
>> cable.
>> When i monitor on the PC side using Network Monitor,
>> the PC receives the ARP request packet and the PC is replying with
>> acknowledgement.
>> I verified reading the receive status register in PPC, it shows there
>> was FCS error and the EMAC rejects the received packet.
> 
> Which 440 variant are you using? And which PHY (in which connection mode, MII, 
> RGMII...)?
> 
>> Actually i enabled external loop back in PowerPC and made appropriate
>> configuration in PPC and in the PHY chip.I have no issues in receiving
>> the packet.things work absolutely fine.
> 
> Are you doing an internal loopback test (using the loopback test mode of the 
> EMAC, or such a test mode of the PHY) or are you using an real external 
> loopback test, using an external RJ45 loopback connector?
> 
> You might want to take a look at the 4xx POST ethernet driver and tests. It's 
> possible to use internal and external loopback tests here (see 
> CONFIG_SYS_POST_ETHER_EXT_LOOPBACK).
> 
>> but when it comes to peer to 
>> peer communication, i have problem.. should i doubt on my hardware??
> 
> Sure. If it's not working then it's always possible that such problems result 
> from hardware issues.
> 
>> what 
>> can be the possibilities?? has anyone faced such an issue?
> 
> I suggest you check your PHY and it's components. Sometimes a wrong resistor 
> or capacitor can cause such or similar problems.
> 
> Best regards,
> Stefan
> 
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