Traffic capture of raw primitives #54
Description
From playing around with fejkon with some actual FC traffic it has become clear that there will be a need to capture behavior on the primitives.
For example when debugging why Brocade loopbacks wouldn't come up in #26 it seems the Brocade switch sends a bunch of primitives that fejkon 1) does not know about and 2) implementing would be infeasible.
Switching to xcvr <-> xcvr based mode is in progress which means that supporting this kind of traffic will be done, but in order to analyze this kind of low-level traffic there needs to be a way to capture essentially a waveform of the primitives.
I have been thinking about something like this:
csr
+
|
+----v---------+ +------------+
| | | |
+---------+ | +---------->+ Memory <-------+
+-->+ Port 0 +---->+ | | | |
+---------+ | RLE | +------------+ |
+---------+ | Encoder | +------------+ |
+-->+ Port 1 +---->+ | | | |
+---------+ | +---------->+ Memory <-------+
| | | | |
+-----^--------+ +------------+ |
| |
+ |
106.25 MHz |
|
|
+
Data
Writing to a fixed-sized memory should allow one to trigger a ~synchronized capture of Port 0 and 1 being written to two memories encoded using RLE. A simple data format such as 64-bit formatted as 24-bit count | 4-bit metadata | 4-bit K-value | 32-bit value should be fine. 24-bit counter means that a fully idle stream will write out 7x idle frames every second as the counter wrap around is reached. This should be ample for our needs.