> -----Original Message-----
> From: Ruvinskiy, Ray [mailto:[email protected]]
> Sent: Tuesday, April 10, 2012 3:34 PM
> To: [email protected]
> Subject: [E1000-devel] MAC Loopback with 82574L
> 
> Hello,
> 
> I am trying to enable MAC loopback with an 82574L device. The code
> looks roughly as follows:
> 
>     u32 rctl, ctrl;
> 
>     ctrl = E1000_READ_REG(&adapter->hw, E1000_CTRL);
>     ctrl |= (E1000_CTRL_FRCSPD | E1000_CTRL_SPD_1000);
>     ctrl |= (E1000_CTRL_FRCDPX | E1000_CTRL_FD);
> 
>     rctl = E1000_READ_REG(&adapter->hw, E1000_RCTL);
>     rctl |= E1000_RCTL_LBM_MAC;
> 
>     E1000_WRITE_REG(&adapter->hw, E1000_RCTL, rctl);
>     E1000_WRITE_REG(&adapter->hw, E1000_CTRL, ctrl);
> 
> This appears to work if the interface already has link (a cable is
> plugged in). However, it does not work if a cable is not plugged in. I
> do not get link interrupts, and packets I try to send disappear into
> the ether. The values of CTRL and RCTL after the steps above end up
> being 0x40101a49 and  0x04008042, respectively. Incidentally, the same
> steps do work with an i350 card.
> 
> I would appreciate if anyone had any suggestions.
> 
> Thanks,
> 
> Ray

Hello Ray,

If you're only getting the 82574 to pass when it has link, you can try setting 
the CTRL.SLU bit to 1.

For comparison, can you please get me the CTRL and RCTL registers in a "fail" 
scenario as well?

Cheers,
Matthew

> 
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