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[i2c,dv] Update predictions for transfers where a the DUT-Controller …
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…sees NACKs.

This is the start of the modelling process, which is still largely incomplete.
It's not yet very granular at handling things like FIFO queues, resets and interrupts.

Signed-off-by: Harry Callahan <[email protected]>
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hcallahan-lowrisc committed Jul 5, 2024
1 parent 1d9f15f commit 6c39ade
Showing 1 changed file with 90 additions and 16 deletions.
106 changes: 90 additions & 16 deletions hw/ip/i2c/dv/env/i2c_reference_model.sv
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Original file line number Diff line number Diff line change
Expand Up @@ -98,15 +98,25 @@ class i2c_reference_model extends uvm_component;
local i2c_item in_progress_wr_transfer;
local i2c_item in_progress_rd_transfer;

// These queues are used to capture predictions of transfers before pushing them out to the
// scoreboard at the appropriate times.
local i2c_item exp_controller_mode_txn_q[$];
// This queue stores predicted Controller-Mode transfers based upon CSR writes to the DUT.
// As we can potentially enque multiple transfers by writing to the FMTFIFO before
// any transfer has even started, we need to keep a track of the expected ordering of transfers.
// Once we have predicted the transfer to have actually been driven and any data read back, we
// can drop the item from this queue.
local i2c_item prev_item[$];

// DUT-Controller
//
// The following local seq_items are used to construct larger transactions.
// We update the local items as different events occur, then push the item
// into a queue for checking after the end of the transaction has been detected.
// See the header comment for more details.
//
local i2c_item exp_wr_item, prev_wr_item;
local i2c_item exp_rd_item, prev_rd_item, rd_pending_item;
local i2c_item exp_wr_item;
local i2c_item exp_rd_item, rd_pending_item;
local i2c_item rd_pending_q[$]; // Helper-queue : holds partial read transactions
local uint rdata_cnt = 0; // Count data-bytes read in a single transfer (DUT-Controller)

Expand Down Expand Up @@ -165,6 +175,7 @@ class i2c_reference_model extends uvm_component;
super.run_phase(phase);
fork
forever create_target_exp();
forever create_controller_exp();
join_none
endtask: run_phase

Expand Down Expand Up @@ -317,7 +328,7 @@ class i2c_reference_model extends uvm_component;
// the current transfer ends (with an RSTART beginning a new transfer.)
exp_wr_item.rstart_back = 1'b1;
push_complete_write_txn(exp_wr_item);
prev_wr_item = exp_wr_item; // Keep track of the previously pushed item.
prev_item.push_back(exp_wr_item); // Keep track of the previously pushed item.
exp_wr_item = new("exp_wr_item");
end

Expand All @@ -329,8 +340,9 @@ class i2c_reference_model extends uvm_component;
i2c_pkg::READ: begin
exp_rd_item = new("exp_rd_item");
exp_rd_item.bus_op = BusOpRead;
exp_rd_item.dir = i2c_pkg::READ;
exp_rd_item.addr = fbyte[7:1];
if (prev_rd_item != null && prev_rd_item.rstart_back) begin
if (prev_item[$] != null && prev_item[$].rstart_back) begin
exp_rd_item.rstart_front = 1;
end else begin
exp_rd_item.start = 1;
Expand All @@ -340,8 +352,9 @@ class i2c_reference_model extends uvm_component;
i2c_pkg::WRITE: begin
exp_wr_item = new("exp_wr_item");
exp_wr_item.bus_op = BusOpWrite;
exp_wr_item.dir = i2c_pkg::WRITE;
exp_wr_item.addr = fbyte[7:1];
if (prev_wr_item != null && prev_wr_item.rstart_back) begin
if (prev_item[$] != null && prev_item[$].rstart_back) begin
exp_wr_item.rstart_front = 1;
end else begin
exp_wr_item.start = 1;
Expand Down Expand Up @@ -369,7 +382,7 @@ class i2c_reference_model extends uvm_component;
exp_wr_item.stop = stop;
if (stop) begin
push_complete_write_txn(exp_wr_item);
prev_wr_item = exp_wr_item; // Keep track of the previously pushed item.
prev_item.push_back(exp_wr_item); // Keep track of the previously pushed item.
exp_wr_item = new("exp_wr_item");
end
end
Expand Down Expand Up @@ -407,7 +420,7 @@ class i2c_reference_model extends uvm_component;
// reads from 'rdata'.
`downcast(tmp_rd_item, exp_rd_item.clone());
rd_pending_q.push_back(tmp_rd_item);
prev_rd_item = tmp_rd_item; // Keep track of the previously pushed item.
prev_item.push_back(tmp_rd_item); // Keep track of the previously pushed item.

// If this read also set the 'stop' bit to end the transaction, clear the
// temporary variable we use to accumulate chained reads.
Expand All @@ -431,10 +444,29 @@ class i2c_reference_model extends uvm_component;
begin
i2c_item temp_item;
`downcast(temp_item, wr_item.clone());
controller_mode_wr_port.write(temp_item);
exp_controller_mode_txn_q.push_back(temp_item);
end
endtask: push_complete_write_txn

// Push DUT-Controller read transfer items to the scoreboard once all data for the transfer
// has been received.
//
task push_complete_read_txn(i2c_item rd_item);
// If we wrote to the FMTFIFO while in-reset or host/controller-mode was
// inactive, break here so we don't push the expectation for checking.
if (cfg.under_reset || !(`gmv(ral.ctrl.enablehost))) return;

begin
i2c_item temp_item;
`downcast(temp_item, rd_item.clone());
exp_controller_mode_txn_q.push_back(temp_item);
end

// Zero-out the pending item, though we will soon drop it for a new
// item the next time we go around and pick up the new FMTFIFO write.
rd_pending_item.clear_all();
endtask: push_complete_read_txn

// Complete forming our expectations of DUT-Controller read items by capturing data read from the
// RXFIFO and adding it into the items created when we started a read xfer in the fmtfifo.
//
Expand Down Expand Up @@ -492,14 +524,7 @@ class i2c_reference_model extends uvm_component;
rdata_cnt = 0;
rd_pending_item.data_ack_q.push_back(i2c_pkg::NACK);

if (!cfg.under_reset) begin
i2c_item tmp_rd_item;
`downcast(tmp_rd_item, rd_pending_item.clone());
controller_mode_rd_port.write(tmp_rd_item);
// Zero-out the pending item, though we will soon drop it for a new
// item the next time we go around and pick up the new FMTFIFO write.
rd_pending_item.clear_all();
end
push_complete_read_txn(rd_pending_item);
end else begin
rd_pending_item.data_ack_q.push_back(i2c_pkg::ACK);
end
Expand All @@ -508,6 +533,55 @@ class i2c_reference_model extends uvm_component;

endtask: rdata_read

// Fuse data from both the i2c and tl_ul interface to create predictions for
// DUT-Controller transfers.
//
virtual task create_controller_exp();
i2c_item csr_pred_xfer;
i2c_item inp_xfer; // in_progress_xfer
i2c_pkg::acknack_e data_ack_q[$];

controller_mode_in_progress_fifo.get(inp_xfer);
`DV_CHECK(inp_xfer.state inside {StNone, StStarted})

// First, wait until we see the Target's ACK/NACK response to the address+dir byte.
// This tells us if our transfer was accepted by anyone.
wait(inp_xfer.state == StAddrByteAckRcvd);

`uvm_info(`gfn, $sformatf(
"create_controller_exp() got inp_xfer : (address=2'h%2x, rw=1'b%b (%0s))",
inp_xfer.addr, inp_xfer.dir, inp_xfer.dir.name()), UVM_HIGH)

// If the address byte was NACK'd, we may just end up sending a STOP immediately, depending on
// if the software chose to clear any FMTFIFO state in response to the NACK.
// If not, we loop to capture all the data-byte ACKs from in-progress transfers.
fork
wait(inp_xfer.state == StStopped);
forever begin
wait(inp_xfer.state == StDataByteRcvd);
wait(inp_xfer.state == StDataByteAckRcvd);
data_ack_q.push_back(i2c_pkg::acknack_e'(inp_xfer.data_ack_q[$]));
end
join_any

// Wait until we have made a prediction based on the CSR accesses only.
wait(exp_controller_mode_txn_q.size > 0);
csr_pred_xfer = exp_controller_mode_txn_q.pop_front();

// If we see a NACK from the Target, then update the prediction
if (inp_xfer.addr_ack == i2c_pkg::NACK) csr_pred_xfer.addr_ack = i2c_pkg::NACK;
// Update the data acks with our observations
foreach (csr_pred_xfer.data_ack_q[i]) csr_pred_xfer.data_ack_q[i] = bit'(data_ack_q[i]);

// Now that we have updated the predicted transfer, push it to the scoreboard for checking
case (csr_pred_xfer.bus_op)
BusOpRead: controller_mode_rd_port.write(csr_pred_xfer);
BusOpWrite: controller_mode_wr_port.write(csr_pred_xfer);
endcase
void'(prev_item.pop_front());

endtask : create_controller_exp

// This task generates DUT-Target transfer expectations
//
// Previously, these expectations were formed by taking the stimulus items directly from the
Expand Down

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