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Set up basic plugin architecture for CSRs in RISC-V - #306

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TheDeepestSpace merged 1 commit into
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boris/zicsr-special-regs
Sep 28, 2026
Merged

Set up basic plugin architecture for CSRs in RISC-V#306
TheDeepestSpace merged 1 commit into
mainfrom
boris/zicsr-special-regs

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@TheDeepestSpace

@TheDeepestSpace TheDeepestSpace commented Sep 28, 2026 •
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See MAS for updates

TheDeepestSpace
TheDeepestSpace commented Sep 28, 2026
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Comment thread src/ext/zicsr/csr_data.sv

// asynchronous read
assign csr_data.value = csrs[csr_request.address];
csr_plugin

@TheDeepestSpace TheDeepestSpace Sep 28, 2026

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what we'll likely do in the future is auto-generate this file from some sort of YAML configuration, since this is gonna get pretty repetitive quick. This way it might be easier to validate too. I'm not confident that csr_plugin will stand the test of time, i am positive we will need to extend it for more involved CSRs as well is see what the semantics of more complicated CSRs will do to this abstraction

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github-actions Bot commented Sep 28, 2026

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📊 Synthesis & Hardening Report Summary Diff

  • RV32I

    • DE1-SoC synthesis

      • Fitter summary

        @@ -1,4 +1,4 @@
-Fitter Status : Successful - Sun Sep 27 23:06:17 2026
+Fitter Status : Successful - Mon Sep 28 01:49:46 2026
 Quartus Prime Version : 25.1std.0 Build 1129 10/21/2025 SC Lite Edition
 Revision Name : utoss-risc-v
 Top-level Entity Name : top

      • Fitter by entity
        No changes detected

      • Timing
        No changes detected

    • Nangate45 hardening

      • Utilization
        No changes detected

      • Gate breakdown
        No changes detected

  • RV32IZbb_Zbkb

    • DE1-SoC synthesis

      • Fitter summary

        @@ -1,4 +1,4 @@
-Fitter Status : Successful - Sun Sep 27 23:04:35 2026
+Fitter Status : Successful - Mon Sep 28 01:48:43 2026
 Quartus Prime Version : 25.1std.0 Build 1129 10/21/2025 SC Lite Edition
 Revision Name : utoss-risc-v
 Top-level Entity Name : top

      • Fitter by entity
        No changes detected

      • Timing
        No changes detected

    • Nangate45 hardening

      • Utilization
        No changes detected

      • Gate breakdown
        No changes detected

  • RV32IZicsr

    • DE1-SoC synthesis

      • Fitter summary

        @@ -1,4 +1,4 @@
-Fitter Status : Successful - Sun Sep 27 23:05:48 2026
+Fitter Status : Successful - Mon Sep 28 01:49:56 2026
 Quartus Prime Version : 25.1std.0 Build 1129 10/21/2025 SC Lite Edition
 Revision Name : utoss-risc-v
 Top-level Entity Name : top

      • Fitter by entity
        No changes detected

      • Timing
        No changes detected

    • Nangate45 hardening

      • Utilization

        @@ -1,21 +1,23 @@
 | Hierarchy / Module                                                   | Total Cells |    Area (um^2) | Comb Cells |      Comb Area | Seq Cells |       Seq Area |
 |----------------------------------------------------------------------|-------------|----------------|------------|----------------|-----------|----------------|
-| top                                                                  |      620552 |     1109516.86 |     483392 |      489279.34 |    137160 |      620237.52 |
-| utoss_riscv$top.core                                                 |      602961 |     1071449.33 |     469993 |      470168.03 |    132968 |      601281.30 |
+| top                                                                  |       28315 |       55908.94 |      22195 |       28234.30 |      6120 |       27674.64 |
+| utoss_riscv$top.core                                                 |       10654 |       17832.91 |       8726 |        9114.49 |      1928 |        8718.42 |
 | ALU$top.core.u_execute_stage.alu                                     |        1040 |        1171.46 |       1040 |        1171.46 |         0 |           0.00 |
 | ALUdecoder$top.core.u_decode_stage.instruction_decode.instanceALUDec |          24 |          23.67 |         24 |          23.67 |         0 |           0.00 |
 | Instruction_Decode$top.core.u_decode_stage.instruction_decode        |         148 |         140.71 |        148 |         140.71 |         0 |           0.00 |
 | MemoryLoader$top.core.u_write_back_stage.memory_loader               |         102 |         104.80 |        102 |         104.80 |         0 |           0.00 |
 | control_fsm$top.core.u_decode_stage.u_ctrl                           |          27 |          28.20 |         27 |          28.20 |         0 |           0.00 |
-| csr_data$top.core.u_decode_stage.u_csr_unit.u_csr_data               |      592379 |     1053873.91 |     461307 |      461166.33 |    131072 |      592707.58 |
+| csr_data$top.core.u_decode_stage.u_csr_unit.u_csr_data               |         204 |         318.93 |        172 |         174.23 |        32 |         144.70 |
 | csr_decode$top.core.u_decode_stage.u_csr_unit.u_csr_decode           |          71 |          57.46 |         71 |          57.46 |         0 |           0.00 |
-| csr_unit$top.core.u_decode_stage.u_csr_unit                          |      592450 |     1053931.37 |     461378 |      461223.78 |    131072 |      592707.58 |
+| csr_plugin$top.core.u_decode_stage.u_csr_unit.u_csr_data.u_mhartid   |           0 |           0.00 |          0 |           0.00 |         0 |           0.00 |
+| csr_plugin$top.core.u_decode_stage.u_csr_unit.u_csr_data.u_mscratch  |         172 |         284.89 |        140 |         140.18 |        32 |         144.70 |
+| csr_unit$top.core.u_decode_stage.u_csr_unit                          |         275 |         376.39 |        243 |         231.69 |        32 |         144.70 |
 | csr_wb$top.core.u_write_back_stage.u_csr_wb                          |         131 |         113.58 |        131 |         113.58 |         0 |           0.00 |
-| decode_stage$top.core.u_decode_stage                                 |      598165 |     1063587.17 |     466069 |      466249.06 |    132096 |      597338.11 |
+| decode_stage$top.core.u_decode_stage                                 |        5858 |        9970.74 |       4802 |        5195.51 |      1056 |        4775.23 |
 | execute_stage$top.core.u_execute_stage                               |        1504 |        1732.72 |       1504 |        1732.72 |         0 |           0.00 |
 | fetch_stage$top.core.u_fetch_stage                                   |         539 |         919.30 |        442 |         480.66 |        97 |         438.63 |
 | hazard_unit$top.core.u_hazard_unit                                   |         157 |         184.60 |        156 |         180.08 |         1 |           4.52 |
 | memory_stage$top.core.u_memory_stage                                 |          68 |          69.96 |         68 |          69.96 |         0 |           0.00 |
-| registerFile$top.core.u_decode_stage.RegFile                         |        5438 |        9325.96 |       4414 |        4695.43 |      1024 |        4630.53 |
+| registerFile$top.core.u_decode_stage.RegFile                         |        5306 |        9264.51 |       4282 |        4633.99 |      1024 |        4630.53 |
 | write_back_stage$top.core.u_write_back_stage                         |         379 |         368.68 |        379 |         368.68 |         0 |           0.00 |
-| memory_map$top.u_memory_map                                          |       17591 |       38067.53 |      13399 |       19111.30 |      4192 |       18956.22 |
+| memory_map$top.u_memory_map                                          |       17661 |       38076.04 |      13469 |       19119.81 |      4192 |       18956.22 |

      • Gate breakdown

        @@ -3,34 +3,34 @@
 ====================================================================
 Cell Type        |      Count |  Total Area (um^2) |   % Area
 --------------------------------------------------------------------
-DFF_X1           |     137160 |          620237.52 |   55.90%
-OAI22_X1         |     133190 |          177142.70 |   15.97%
-INV_X1           |     133293 |           70911.88 |    6.39%
-OAI21_X1         |      62280 |           66265.92 |    5.97%
-AOI21_X1         |      53517 |           56942.09 |    5.13%
-NOR3_X1          |      22021 |           23430.34 |    2.11%
-MUX2_X1          |      12206 |           22727.57 |    2.05%
-AOI211_X1        |      12892 |           17146.36 |    1.55%
-NOR2_X1          |      17945 |           14320.11 |    1.29%
-NAND3_X1         |       9081 |            9662.18 |    0.87%
-NAND2_X1         |      11958 |            9542.48 |    0.86%
-OAI211_X1        |       6501 |            8646.33 |    0.78%
-OAI221_X1        |       1751 |            2794.60 |    0.25%
-AOI221_X1        |       1546 |            2467.42 |    0.22%
-AOI222_X1        |        871 |            1853.49 |    0.17%
-AOI22_X1         |       1176 |            1564.08 |    0.14%
-OR3_X1           |        899 |            1195.67 |    0.11%
-OR2_X1           |        883 |             939.51 |    0.08%
-AND2_X1          |        711 |             756.50 |    0.07%
-AND3_X1          |        320 |             425.60 |    0.04%
-XNOR2_X1         |        137 |             218.65 |    0.02%
-XOR2_X1          |         69 |             110.12 |    0.01%
-NAND4_X1         |         57 |              75.81 |    0.01%
-NOR4_X1          |         36 |              47.88 |    0.00%
-OR4_X1           |         17 |              27.13 |    0.00%
-OAI222_X1        |         12 |              25.54 |    0.00%
-AND4_X1          |         13 |              20.75 |    0.00%
-OAI33_X1         |         10 |              18.62 |    0.00%
+DFF_X1           |       6120 |           27674.64 |   49.50%
+MUX2_X1          |       5084 |            9466.41 |   16.93%
+OAI21_X1         |       2139 |            2275.90 |    4.07%
+AOI222_X1        |        879 |            1870.51 |    3.35%
+NOR2_X1          |       2249 |            1794.70 |    3.21%
+AOI21_X1         |       1627 |            1731.13 |    3.10%
+OAI22_X1         |       1272 |            1691.76 |    3.03%
+INV_X1           |       2240 |            1191.68 |    2.13%
+AOI22_X1         |        856 |            1138.48 |    2.04%
+AOI221_X1        |        686 |            1094.86 |    1.96%
+OAI211_X1        |        769 |            1022.77 |    1.83%
+NAND2_X1         |       1069 |             853.06 |    1.53%
+NAND3_X1         |        728 |             774.59 |    1.39%
+AOI211_X1        |        543 |             722.19 |    1.29%
+OAI221_X1        |        450 |             718.20 |    1.28%
+AND2_X1          |        477 |             507.53 |    0.91%
+OR2_X1           |        380 |             404.32 |    0.72%
+NOR3_X1          |        336 |             357.50 |    0.64%
+XNOR2_X1         |        137 |             218.65 |    0.39%
+XOR2_X1          |         69 |             110.12 |    0.20%
+NAND4_X1         |         62 |              82.46 |    0.15%
+NOR4_X1          |         40 |              53.20 |    0.10%
+AND3_X1          |         34 |              45.22 |    0.08%
+OR3_X1           |         28 |              37.24 |    0.07%
+OR4_X1           |         15 |              23.94 |    0.04%
+OAI222_X1        |         11 |              23.41 |    0.04%
+AND4_X1          |         13 |              20.75 |    0.04%
+OAI33_X1         |          2 |               3.72 |    0.01%
 --------------------------------------------------------------------
-TOTAL            |     620552 |         1109516.86 | 100.00%
+TOTAL            |      28315 |           55908.94 | 100.00%
 ====================================================================

Comparing synthesis & hardening results from main branch vs. this PR

@TheDeepestSpace
TheDeepestSpace merged commit 3f15685 into main Sep 28, 2026
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