Add obi_to_apb module

Bender.yml

@@ -21,6 +21,7 @@ sources:
   - src/obi_intf.sv
   - src/obi_rready_converter.sv
   - src/apb_to_obi.sv
+  - src/obi_to_apb.sv
   # Level 3
   - src/obi_atop_resolver.sv
   - src/obi_cut.sv

Readme.md

@@ -20,6 +20,8 @@ Most IPs will also support a SystemVerilog `interface` variant, also based on `O
 - `obi_err_sbr.sv`: A error subordinate, responding with the error bit set.
 - `obi_sram_shim.sv`: An adapter for a standard sram.
 - `obi_atop_resolver.sv`: An atomics filter, resolving atomic operations on an exclusive bus.
+- `apb_to_obi.sv`: A protocol converter from APB to OBI.
+- `obi_to_apb.sv`: A protocol converter from OBI to APB.
 
 ## License
 Solderpad Hardware License, Version 0.51

src/obi_to_apb.sv

@@ -0,0 +1,167 @@
+// Copyright 2025 ETH Zurich and University of Bologna.
+// Solderpad Hardware License, Version 0.51, see LICENSE for details.
+// SPDX-License-Identifier: SHL-0.51
+
+// Michael Rogenmoser <michaero@iis.ee.ethz.ch>
+
+`include "common_cells/assertions.svh"
+
+/// An OBI to APB adapter.
+module obi_to_apb #(
+  /// The configuration of the subordinate port (input port).
+  parameter      obi_pkg::obi_cfg_t ObiCfg = obi_pkg::ObiDefaultConfig,
+  /// The OBI request struct for the subordinate port (input port).
+  parameter type obi_req_t = logic,
+  /// The OBI response struct for the subordinate port (input port).
+  parameter type obi_rsp_t = logic, // OBI response struct
+  /// The APB request struct for the manager port (output port).
+  parameter type apb_req_t = logic, // APB request struct
+  /// The APB response struct for the manager port (output port).
+  parameter type apb_rsp_t = logic, // APB response struct
+  /// Enable gnt/rvalid in same cycle.
+  parameter bit EnableSameCycleRsp = 1'b0
+) (
+  input  logic clk_i,
+  input  logic rst_ni,
+  // Subordinate OBI port.
+  input  obi_req_t obi_req_i,
+  output obi_rsp_t obi_rsp_o,
+  // Manager APB port.
+  output apb_req_t apb_req_o,
+  input  apb_rsp_t apb_rsp_i
+);
+
+  logic [ObiCfg.AddrWidth-1:0] addr;
+  logic [ObiCfg.DataWidth-1:0] wdata;
+  logic we;
+  logic [ObiCfg.DataWidth/8-1:0] be;
+  logic [2:0] prot;
+
+  assign apb_req_o.paddr  = addr;
+  assign apb_req_o.pwrite = we;
+  // OBI expects '1 on writes, APB sets pstrb to '0 on reads.
+  assign apb_req_o.pstrb  = we ? be : '0;
+  assign apb_req_o.pwdata = wdata;
+  if (ObiCfg.OptionalCfg.UseProt) begin : gen_pprot
+    // Bit 2: inverted bit 0 of OBI prot
+    assign apb_req_o.pprot[2] = ~prot[2];
+    // Bit 1: secure access only for machine mode
+    assign apb_req_o.pprot[1] = ~(prot[1] & prot[0]);
+    // Bit 0: privileged for machine mode and supervisor mode
+    assign apb_req_o.pprot[0] = prot[1];
+  end else begin : gen_no_pprot
+    // OBI does not enable prot, so we set it to priviledged, secure, instruction.
+    assign apb_req_o.pprot = 3'b101;
+  end
+
+  assign obi_rsp_o.r.rdata = apb_rsp_i.prdata;
+  assign obi_rsp_o.r.err   = apb_rsp_i.pslverr;
+  assign obi_rsp_o.r.r_optional = '0; // No optional R feature supported at the moment.
+
+  if (!EnableSameCycleRsp) begin : gen_hs_buffers
+    logic tsxn_in_progress;
+    logic [ObiCfg.IdWidth-1:0] aid_q;
+    logic [ObiCfg.AddrWidth-1:0] addr_q;
+    logic [ObiCfg.DataWidth-1:0] wdata_q;
+    logic we_q;
+    logic [ObiCfg.DataWidth/8-1:0] be_q;
+    logic [2:0] prot_q;
+
+    assign apb_req_o.psel = obi_req_i.req | tsxn_in_progress;
+    assign apb_req_o.penable = tsxn_in_progress;
+    assign obi_rsp_o.gnt = ~tsxn_in_progress;
+    assign obi_rsp_o.rvalid = apb_rsp_i.pready & tsxn_in_progress;
+    // Mirror AID to RID
+    assign obi_rsp_o.r.rid = aid_q;
+
+    assign addr = tsxn_in_progress ? addr_q : obi_req_i.a.addr;
+    assign wdata = tsxn_in_progress ? wdata_q : obi_req_i.a.wdata;
+    assign we = tsxn_in_progress ? we_q : obi_req_i.a.we;
+    assign be = tsxn_in_progress ? be_q : obi_req_i.a.be;
+
+    always_ff @(posedge clk_i or negedge rst_ni) begin
+      if (!rst_ni) begin
+        tsxn_in_progress <= 1'b0;
+        aid_q <= '0;
+        addr_q <= '0;
+        wdata_q <= '0;
+        we_q <= 1'b0;
+        be_q <= '0;
+      end else begin
+        tsxn_in_progress <= apb_req_o.psel & ~apb_rsp_i.pready;
+        if (obi_req_i.req & obi_rsp_o.gnt) begin
+          aid_q <= obi_req_i.a.aid;
+          addr_q <= obi_req_i.a.addr;
+          wdata_q <= obi_req_i.a.wdata;
+          we_q <= obi_req_i.a.we;
+          be_q <= obi_req_i.a.be;
+        end
+      end
+    end
+    if (ObiCfg.OptionalCfg.UseProt) begin : gen_prot
+      always_ff @(posedge clk_i or negedge rst_ni) begin
+        if (!rst_ni) begin
+          prot <= 3'b101; // Privileged, secure, instruction.
+        end else if (obi_req_i.req & obi_rsp_o.gnt) begin
+          prot <= obi_req_i.a.a_optional.prot;
+        end
+      end
+    end else begin : gen_no_prot
+      assign prot = 3'b101; // Privileged, secure, instruction.
+    end
+
+  end else begin : gen_no_hs_buffers
+    logic psel_q;
+    assign apb_req_o.psel = obi_req_i.req;
+    assign apb_req_o.penable = psel_q;
+    assign obi_rsp_o.gnt = apb_rsp_i.pready;
+    assign obi_rsp_o.rvalid = apb_rsp_i.pready;
+    // Mirror AID to RID
+    assign obi_rsp_o.r.rid = obi_req_i.a.aid;
+    assign addr = obi_req_i.a.addr;
+    assign wdata = obi_req_i.a.wdata;
+    assign we = obi_req_i.a.we;
+    assign be = obi_req_i.a.be;
+    if (ObiCfg.OptionalCfg.UseProt) begin : gen_prot
+      assign prot = obi_req_i.a.a_optional.prot;
+    end else begin : gen_no_prot
+      assign prot = 3'b101; // Privileged, secure, instruction.
+    end
+
+    always_ff @(posedge clk_i or negedge rst_ni) begin
+      if (!rst_ni) begin
+        psel_q <= 1'b0;
+      end else begin
+        psel_q <= obi_req_i.req & ~apb_rsp_i.pready;
+      end
+    end
+  end
+
+
+  // ----------
+  // Assertions
+  // ----------
+
+  `ASSERT_INIT(no_rready, ObiCfg.UseRReady == 0,
+      "RReady not supported in OBI to APB conversion")
+  `ASSERT_INIT(no_atop, ObiCfg.OptionalCfg.UseAtop == 0,
+      "ATOP not supported in OBI to APB conversion")
+  `ASSERT_INIT(no_memtype, ObiCfg.OptionalCfg.UseMemtype == 0,
+      "Memtype not supported in OBI to APB conversion")
+  `ASSERT_INIT(no_debug, ObiCfg.OptionalCfg.UseDbg == 0,
+      "Debug not supported in OBI to APB conversion")
+  `ASSERT_INIT(no_integrity, !ObiCfg.Integrity,
+      "Integrity not supported!")
+   `ASSERT_INIT(no_achk, ObiCfg.OptionalCfg.AChkWidth == 0,
+      "ACHK field not supported!")
+  `ASSERT_INIT(equal_wdata_width, $bits(apb_req_o.pwdata) == $bits(obi_req_i.a.wdata),
+      "WDATA width mismatch between APB and OBI ports!")
+  `ASSERT_INIT(equal_be_width, $bits(apb_req_o.pstrb) == $bits(obi_req_i.a.be),
+      "Strobe width mismatch between APB and OBI ports!")
+  `ASSERT_INIT(equal_rdata_width, $bits(apb_rsp_i.prdata) == $bits(obi_rsp_o.r.rdata),
+      "RDATA width mismatch between APB and OBI ports!")
+  `ASSERT_INIT(equal_addr_width, $bits(apb_req_o.paddr) == $bits(obi_req_i.a.addr),
+      "Address width mismatch between APB and OBI ports!")
+
+
+endmodule