XGMII Driver initialization incomplete

The XGMII Driver initialization is incomplete resulting in a corrupted word on the first transfer.

The _XGMII_Bus helper class sets it’s value to XGMII IDLE during the __init__: https://github.com/cocotb/cocotb/blob/97e28803308d09d2bd885e4279d5036ef9861d42/cocotb/drivers/xgmii.py#L61-L83

But this value is never read during initialization of XGMII(Driver) … https://github.com/cocotb/cocotb/blob/97e28803308d09d2bd885e4279d5036ef9861d42/cocotb/drivers/xgmii.py#L122-L140

… and as reading the value clears the internal _integer buffer of the helper class … https://github.com/cocotb/cocotb/blob/97e28803308d09d2bd885e4279d5036ef9861d42/cocotb/drivers/xgmii.py#L104-L113

… the first word of the first transaction (actually the PREAMBLE and START byte) is OR’ed with the IDLE value corrupting the transmission.

One way of fixing would be to simply read the value of the bus during __init__ of XGMII(Driver) and thus clearing the buffer.

self.signal <= self.bus.value

Alternatively (and maybe cleaner) we could remove the default value of the helper class and use the idle helper of XGMII(Driver).

I’ll submit a pull for the latter, as I feel it’s cleaner. Thoughts?

[ktbarrett]

This was resolved by #1905, right?

[ktbarrett]

@ecg173-bi Have a look here at the type annotation for the XGMIIDriver, the signal argument is supposed to be a sim handle not a Bus. I’d suggest the following, assuming stream_in is your XGMII bus.

XGMII(dut.stream_in, dut.stream_in_gmii_clk, interleaved = True)