[prim_alert*/prim_esc*] Rework placement of size_only bufs/flops
This slightly reworks the placement of size_only bufs and flops.
In particular, all diff input and outputs should now either go through a
size_only flop or a size_only buf.
Signed-off-by: Michael Schaffner <msf@opentitan.org>
diff --git a/hw/ip/prim/rtl/prim_alert_receiver.sv b/hw/ip/prim/rtl/prim_alert_receiver.sv
index bfc1baf..338387c 100644
--- a/hw/ip/prim/rtl/prim_alert_receiver.sv
+++ b/hw/ip/prim/rtl/prim_alert_receiver.sv
@@ -56,15 +56,25 @@
/////////////////////////////////
// decode differential signals //
/////////////////////////////////
- logic alert_level, alert_sigint;
+ logic alert_level, alert_sigint, alert_p, alert_n;
+
+ // This prevents further tool optimizations of the differential signal.
+ prim_buf #(
+ .Width(2)
+ ) u_prim_buf (
+ .in_i({alert_tx_i.alert_n,
+ alert_tx_i.alert_p}),
+ .out_o({alert_n,
+ alert_p})
+ );
prim_diff_decode #(
.AsyncOn(AsyncOn)
- ) i_decode_alert (
+ ) u_decode_alert (
.clk_i,
.rst_ni,
- .diff_pi ( alert_tx_i.alert_p ),
- .diff_ni ( alert_tx_i.alert_n ),
+ .diff_pi ( alert_p ),
+ .diff_ni ( alert_n ),
.level_o ( alert_level ),
.rise_o ( ),
.fall_o ( ),
@@ -78,33 +88,43 @@
typedef enum logic [1:0] {Idle, HsAckWait, Pause0, Pause1} state_e;
state_e state_d, state_q;
logic ping_rise;
- logic ping_tog, ping_tog_dp, ping_tog_qp, ping_tog_dn, ping_tog_qn;
- logic ack, ack_dp, ack_qp, ack_dn, ack_qn;
+ logic ping_tog_pd, ping_tog_pq, ping_tog_dn, ping_tog_nq;
+ logic ack_pd, ack_pq, ack_dn, ack_nq;
logic ping_req_d, ping_req_q;
logic ping_pending_d, ping_pending_q;
// signal ping request upon positive transition on ping_req_i
// signalling is performed by a level change event on the diff output
assign ping_req_d = ping_req_i;
- assign ping_rise = ping_req_i && !ping_req_q;
- assign ping_tog = (ping_rise) ? ~ping_tog_qp : ping_tog_qp;
+ assign ping_rise = ping_req_i && !ping_req_q;
+ assign ping_tog_pd = (ping_rise) ? ~ping_tog_pq : ping_tog_pq;
+
+ assign ack_dn = ~ack_pd;
+ assign ping_tog_dn = ~ping_tog_pd;
// This prevents further tool optimizations of the differential signal.
- prim_buf u_prim_buf_ack_p (
- .in_i(ack),
- .out_o(ack_dp)
+ prim_generic_flop #(
+ .Width (2),
+ .ResetValue(2'b10)
+ ) u_prim_generic_flop_ack (
+ .clk_i,
+ .rst_ni,
+ .d_i({ack_dn,
+ ack_pd}),
+ .q_o({ack_nq,
+ ack_pq})
);
- prim_buf u_prim_buf_ack_n (
- .in_i(~ack),
- .out_o(ack_dn)
- );
- prim_buf u_prim_buf_ping_p (
- .in_i(ping_tog),
- .out_o(ping_tog_dp)
- );
- prim_buf u_prim_buf_ping_n (
- .in_i(~ping_tog),
- .out_o(ping_tog_dn)
+
+ prim_generic_flop #(
+ .Width (2),
+ .ResetValue(2'b10)
+ ) u_prim_generic_flop_ping (
+ .clk_i,
+ .rst_ni,
+ .d_i({ping_tog_dn,
+ ping_tog_pd}),
+ .q_o({ping_tog_nq,
+ ping_tog_pq})
);
// the ping pending signal is used to in the FSM to distinguish whether the
@@ -115,11 +135,11 @@
assign ping_pending_d = ping_rise | ((~ping_ok_o) & ping_req_i & ping_pending_q);
// diff pair outputs
- assign alert_rx_o.ack_p = ack_qp;
- assign alert_rx_o.ack_n = ack_qn;
+ assign alert_rx_o.ack_p = ack_pq;
+ assign alert_rx_o.ack_n = ack_nq;
- assign alert_rx_o.ping_p = ping_tog_qp;
- assign alert_rx_o.ping_n = ping_tog_qn;
+ assign alert_rx_o.ping_p = ping_tog_pq;
+ assign alert_rx_o.ping_n = ping_tog_nq;
// this FSM receives the four phase handshakes from the alert receiver
// note that the latency of the alert_p/n input diff pair is at least one
@@ -128,7 +148,7 @@
always_comb begin : p_fsm
// default
state_d = state_q;
- ack = 1'b0;
+ ack_pd = 1'b0;
ping_ok_o = 1'b0;
integ_fail_o = 1'b0;
alert_o = 1'b0;
@@ -138,7 +158,7 @@
// wait for handshake to be initiated
if (alert_level) begin
state_d = HsAckWait;
- ack = 1'b1;
+ ack_pd = 1'b1;
// signal either an alert or ping received on the output
if (ping_pending_q) begin
ping_ok_o = 1'b1;
@@ -152,7 +172,7 @@
if (!alert_level) begin
state_d = Pause0;
end else begin
- ack = 1'b1;
+ ack_pd = 1'b1;
end
end
// pause cycles between back-to-back handshakes
@@ -164,7 +184,7 @@
// override in case of sigint
if (alert_sigint) begin
state_d = Idle;
- ack = 1'b0;
+ ack_pd = 1'b0;
ping_ok_o = 1'b0;
integ_fail_o = 1'b1;
alert_o = 1'b0;
@@ -174,18 +194,10 @@
always_ff @(posedge clk_i or negedge rst_ni) begin : p_reg
if (!rst_ni) begin
state_q <= Idle;
- ack_qp <= 1'b0;
- ack_qn <= 1'b1;
- ping_tog_qp <= 1'b0;
- ping_tog_qn <= 1'b1;
ping_req_q <= 1'b0;
ping_pending_q <= 1'b0;
end else begin
state_q <= state_d;
- ack_qp <= ack_dp;
- ack_qn <= ack_dn;
- ping_tog_qp <= ping_tog_dp;
- ping_tog_qn <= ping_tog_dn;
ping_req_q <= ping_req_d;
ping_pending_q <= ping_pending_d;
end
