Allow delaying the last byte to make it easier to exactly time when the
MAC sees the byte. This way, we can test to ensure that everything works
even when valid is only high for one cycle. We can't change signals
once valid goes high, so this is the only way to ensure this kind of
timing.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
We don't need to delay after sending the last byte, and it makes it more
difficult to time subsequent packets correctly.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
We only care about backoff when state=BACKOFF. We can simplify the
calculation by defaulting to loading lfsr into backoff, and special
casing things for state=BACKOFF.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This adds the transmit half of a MAC, supporting 100M and half-duplex.
It's roughly analogous to the axis_(x)gmii_tx modules in Alex
Forencich's ethernet repo. I've taken the approach of moving all state
into the state variable. All decisions are made once and have a
different state for each path. For example, instead of checking against
a "bytes_sent" variable to determine what to do on collision, we have a
different state for each set of actions.
This whole module is heinously complex, especially because of the many
corner cases caused by the spec. I have probably not tested it nearly
enough, but the basics of sending packets have mostly had the bugs wrung
out.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
The downstream TX side of the MII is almost the same as the upstream RX
side of the MII. However, MACs may never generate TX_ER, so I will be
leaving it out. TO allow testing this, make the err signal optional.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Detecting non-clock signal edges with RisingEdge and FallingEdge is not
very robust, and is recommended against. Track edges manually.
Fixes: f6f3f02 ("Add phy_core")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Although the least-significant bit of sd_delay is driven by an SB_IO (if
we are synthesizing), the other bits need to be initialized.
Fixes: d8ce165 ("pmd: Delay signal_status/detect until data is valid")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
The condition for determining s_axis_ready only looks at whether we are
currently full, not whether we will be full on the next cycle (which is
what matters). Make it take into account whether we are going to
increment s_ptr during the current cycle. Also increase the ratio to
ensure we trigger this case, as a ration of 2 doesn't make the slave
slow enough to catch this.
Fixes: 52325f2 ("Add AXI stream replay buffer")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
If the lower bits of m_ptr is the same as s_ptr when we get s_axis_last
(that is, we are full), then we will immediately end (since m_ptr will
equal last_ptr). Fix this by including all of s_ptr in last_ptr.
Fixes: 52325f2 ("Add AXI stream replay buffer")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This adds the integrated PMD module to be used with the DP83223. It
contains NRZI en/decoding as well as the I/O interfaces. The rx I/O was
added a while back, and the tx is just the I/O cell.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Most other modules in the recieve path are reset when signal_status goes
low. This one didn't, and it was difficult to test because of this. In
particular, we need to ensure that this module behaves correctly when
switching between different bitstreams (such as for loopback).
While implementing this, I found some bugs in the way that nrzi_valid
was handled: it wasn't saved from when the transfer actually happened,
and the data wasn't qualified properly.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This implements an AXI stream buffer which allows replaying of the first
portion of each packet. The intent is to simplify the implementation of
CSMA/CD. This requires keeping 56 bytes of data to "replay" (slot time
minus the preamble). After these bytes are transmitted, we can only get
late collisions.
We always read from the buffer, as this simplifies the implementation
compared to some kind of hybrid fifo/skid buffer approach. The primary
design problem faced is in determining when it's OK to overwrite the
first byte in the packet. A naïve approach might be to allow overwriting
whenever the slave reads the last byte. However, in the case of a
54-byte packet, we will still need to allow replaying at this point (in
case there is a collision on the last byte). We can't just wait for
m_axis_ready to go high, because that would violate the AXI stream
protocol. To solve this, the slave must assert the done signal when it
is finished with the packet.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Some of the ignores were not updated properly when reworking the
Makefile. Also add tags.
Fixes: 6af697b ("Initial support for post-placement simulation")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This module integrates the PCS with the descrambler, implements the PMA
(which is just the link monitor), and implements loopback and coltest
functions. This is more of the PCS/PMA, but the descrambler is
technically part of the PMD, so it's the "core" instead.
We deviate from the standard in one important way: the link doesn't come
up until the descambler is locked. I think this makes sense, since if
the descrambler isn't locked, then the incoming data will be gibberish.
I suspect this isn't part of the standard because the descrambler
doesn't have a locked output in X3.263, so IEEE would have had to
specify it.
Loopback is actually implemented in the PMD, but it modifies the
behavior in several places. It disables collisions (unless
coltest is enabled). Additionally, we need to force the link up (to
avoid the lengthy stabilization timer), but ensure it is down for at
least once cycle (to ensure the descrambler desynchronizes).
On the test side, we just go through the "happy path," as many of the
edge conditions are tested for in the submodule tests. Several of those
tests are modified so that their helper functions can be reused in this
test. In particular, the rx path is now async so that we can feed it
rx_data.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
The dependencies for the test target never got updated when some modules
were renamed. Fix this.
Fixes: 494ef2a ("pcs: Split into rx/tx")
Fixes: cf0aed4 ("pmd_io: Rename to pmd_dp83223_rx")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This adds an explicit false carrier signal. Trying to determine this
condition the MDIO signals is tricky because BAD_SSD can last over
several cycles of CE. To make things easier, add a signal which is high
only once per event.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Even when signal_status is low, we should still generate data. This
keeps the PCS processes moving along.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This adds support for counters for interesting conditions (disconnects,
PMD phase wraparounds, errors, etc). All the counters are 15 bits
instead of 16, because 16-bit counters have an fmax of 110MHz or so. All
the counters live behind a condition because they ~double the number of
resources used.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
On stretches without transitions, we can lose (or gain) a bit, depending
on how the reciever is reckoning. This can cause spurious test failures
when we get especially unlucky. Keep track of our running disparity
(time-wise, not value-wise) and keep perfect time until we get a
transition (or we start moving back in the right direction).
Signed-off-by: Sean Anderson <seanga2@gmail.com>
When increasing the delay for the recieved data, I forgot to increase
the delay for the signal status as well. Fix this.
Fixes: c02d3f3 ("pmd_io: Calculate wraparound based on state and not state_next")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This better reflects that this is an interface intended to be used with
the DP83223. While we're at it, refactor the module to just handle the
the recieve portion.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
For easier integration, split the PCS into its rx and tx components.
This was already done on the module level, but now they live in separate
files.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Basing the wraparound calculation on state_next is causing problems for
timing. Do it with the state calculations instead. We need to add
another cycle of latency to make this work, since we can't output the
data correctly without knowing the wraparound.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
These inputs were incorrectly marked as LVDS, which was causing problems
for placement. Make them single-ended.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
When writing this initially, I tried to remove some duplicate
conditionals by working with idle_counter_next. However, yosys isn't
smart enough to rewrite the calculation in terms of idle_counter, so do
it ourselves. This breaks up the critical path.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
The critical path often includes the unlock timer. Switch to an lfsr
implementation. This saves around 20 LUTs and reduces the critical path
from the carry chain (and the or reduction) to just the and reduction.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
While manually dumping signals with a macro works OK for standalone
modules, it doesn't work when multiple modules are included. Instead,
create a second top-level module to dump signals. Inspired (once again)
by [1].
[1] https://github.com/steveicarus/iverilog/issues/376#issuecomment-709907692
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This aligns the signal naming with what is used by other modules (IEEE
names for external signals, and something else for internal).
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Yosys is very verbose, so I usually run it quietly. However, it may be
usefult to review synthesis logs when debugging.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This isn't really useful for most modules (since the placement info is
if they were the only thing instantiated), but it should be a good base.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
As it turns out,
reg foo = 0;
is not the same as
reg foo; initial foo = 0;
but instead is equivalent to
reg foo; always @(*) foo = 0;
This is rather silly. Convert all existing (lucky) examples to the
second form.
Signed-off-by: Sean Anderson <seanga2@gmail.com>
The singal-ended to differential conversion will be done by the
transceiver (by the ECL interface circuit).
Signed-off-by: Sean Anderson <seanga2@gmail.com>
Sean Anderson