IO: move tristate handling to top level

src/i3c.f

@@ -28,7 +28,6 @@
 ${I3C_ROOT_DIR}/src/csr/I3CCSR_pkg.sv
 ${I3C_ROOT_DIR}/src/ctrl/controller_pkg.sv
 ${I3C_ROOT_DIR}/src/i3c_pkg.sv
-${I3C_ROOT_DIR}/src/phy/buf_od.sv
 ${I3C_ROOT_DIR}/src/phy/buf_pp.sv
 ${I3C_ROOT_DIR}/src/phy/bufs.sv
 ${I3C_ROOT_DIR}/src/phy/i3c_phy.sv

src/i3c_wrapper.sv

@@ -264,16 +264,27 @@ module i3c_wrapper #(
   assign sda_o = sda_phy2io;
   assign sel_od_pp_o = sel_od_pp;
 `else
+  logic scl_drive_low, sda_drive_low;
+  logic sda_od, scl_od;
+  wire i3c_scl_pp_io, i3c_scl_pp_io;
+  assign scl_drive_low = ~scl_phy2io;
+  assign sda_drive_low = ~sda_phy2io;
+
   i3c_io xio (
       .scl_i(scl_phy2io),
       .sda_i(sda_phy2io),
       .scl_o(scl_io2phy),
       .sda_o(sda_io2phy),
       .sel_od_pp_i(sel_od_pp),
-      .scl_io(i3c_scl_io),
-      .sda_io(i3c_sda_io)
+      .scl_io(i3c_scl_pp_io),
+      .sda_io(i3c_sda_pp_io)
   );
-`endif
 
+  assign sda_od = sda_drive_low ? 1'b0 : 1'bz;
+  assign scl_od = scl_drive_low ? 1'b0 : 1'bz;
+  assign i3c_sda_io = sel_od_pp ? i3c_sda_pp_io : sda_od;
+  assign i3c_scl_io = sel_od_pp ? i3c_scl_pp_io : scl_od;
+
+`endif
 
 endmodule

src/phy/buf_pp.sv

@@ -12,7 +12,6 @@
   |  1 |   0| 1   |
   |  1 |   1| x   |
 
-  TODO: Add assertion for when pull_up_en and pull_down_en have the same state
 */
 module buf_pp (
     input  logic pull_up_en,

src/phy/bufs.sv

@@ -2,42 +2,20 @@
 
 `timescale 1ns / 1ps
 
-/*
-  Combined model of the Open-Drain Driver and Push-Pull Driver for the I3C bus lines.
-
-  | sel_driver_i | phy_data_i | phy_data_io |
-  |            0 |          0 |           z |
-  |            0 |          1 |           0 |
-  |            1 |          0 |           0 |
-  |            1 |          1 |           1 |
-*/
 module bufs (
     input logic phy_data_i,
-    input logic sel_od_pp_i,
-    inout wire  phy_data_io
+    output wire phy_data_o
 );
 
   logic phy_data_i_z;
 
   assign phy_data_i_z = ~phy_data_i;
 
-  logic buf_pp_o;
-  wire  buf_od_o;
-
   // Model of a Push-Pull driver
   buf_pp xbuf_pp (
       .pull_up_en(phy_data_i),
       .pull_down_en(phy_data_i_z),
-      .buf_pp_o(buf_pp_o)
+      .buf_pp_o(phy_data_o)
   );
 
-  // Model of an Open-Drain driver
-  buf_od xbuf_od (
-      .drive_low(~phy_data_i),
-      .buf_od_o (buf_od_o)
-  );
-
-  // Mux between OD and PP
-  assign phy_data_io = sel_od_pp_i ? buf_pp_o : buf_od_o;
-
 endmodule

src/phy/i3c_io.sv

@@ -4,11 +4,6 @@
 
 /*
   This module provides IO definition for the I3C Core.
-
-  The Core provides a few IO models, which can be used for different use cases:
-   - simulation
-   - FPGA emulation
-   - silicon synthesis
 */
 
 module i3c_io (
@@ -21,9 +16,6 @@ module i3c_io (
     output logic scl_o,
     output logic sda_o,
 
-    // Open-Drain / Push-Pull control
-    input logic sel_od_pp_i,
-
     // Bus {SCL, SDA}
     inout wire scl_io,
     inout wire sda_io
@@ -32,21 +24,18 @@ module i3c_io (
   // SCL buffers
   bufs xbufs_scl (
       .phy_data_i (scl_i),
-      .sel_od_pp_i(sel_od_pp_i),
-      .phy_data_io(scl_io)
+      .phy_data_o(scl_io)
   );
 
   // SDA buffers
   bufs xbufs_sda (
       .phy_data_i (sda_i),
-      .sel_od_pp_i(sel_od_pp_i),
-      .phy_data_io(sda_io)
+      .phy_data_o(sda_io)
   );
 
   // Bus state is read to provide feedback to the controller
   // Used to resolve bus arbitration and detect bus error conditions
   assign scl_o = scl_io;
   assign sda_o = sda_io;
 
-
 endmodule

verification/cocotb/block/i3c_phy_io/Makefile

@@ -16,7 +16,6 @@ TOPLEVEL     = i3c_phy_io_wrapper
 include $(TEST_DIR)/../../caliptra_common.mk
 
 VERILOG_SOURCES += \
-	$(SRC_DIR)/phy/buf_od.sv \
 	$(SRC_DIR)/phy/buf_pp.sv \
 	$(SRC_DIR)/phy/bufs.sv \
 	$(SRC_DIR)/phy/i3c_io.sv \

verification/cocotb/block/i3c_phy_io/i3c_phy_io_wrapper.sv

@@ -30,6 +30,11 @@ module i3c_phy_io_wrapper (
     logic sda_io2phy;
     logic sel_od_pp;
 
+    logic scl_drive_low, sda_drive_low;
+    logic sda_od, scl_od;
+    assign scl_drive_low = ~scl_phy2io;
+    assign sda_drive_low = ~sda_phy2io;
+
     i3c_phy xphy(
         .clk_i(clk_i),
         .rst_ni(rst_ni),
@@ -50,11 +55,14 @@ module i3c_phy_io_wrapper (
         .sda_i(sda_phy2io),
         .scl_o(scl_io2phy),
         .sda_o(sda_io2phy),
-        .sel_od_pp_i(sel_od_pp),
         .scl_io(scl_io),
         .sda_io(sda_io)
     );
 
+    assign sda_od = sda_drive_low ? 1'b0 : 1'bz;
+    assign scl_od = sda_drive_low ? 1'b0 : 1'bz;
+    assign i3c_sda_io = sel_od_pp ? sda_io : sda_od;
+    assign i3c_scl_io = sel_od_pp ? scl_io : scl_od;
 
     initial
     begin