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Removed CSR mscratchcsw. #925

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merged 2 commits into from
Aug 31, 2023
Merged

Removed CSR mscratchcsw. #925

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6700e15
Removed CSR mscratchcsw.
silabs-oysteink Aug 31, 2023
65b3565
Fixes after review.
silabs-oysteink Aug 31, 2023
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8 changes: 4 additions & 4 deletions bhv/cv32e40x_wrapper.sv
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Original file line number Diff line number Diff line change
Expand Up @@ -614,7 +614,7 @@ endgenerate
.wpt_match_wb_i ( core_i.wb_stage_i.wpt_match_wb_o ),
.mpu_status_wb_i ( core_i.wb_stage_i.mpu_status_wb_o ),
.align_status_wb_i ( core_i.wb_stage_i.align_status_wb_o ),
.csr_mscratchcsw_in_wb_i ( core_i.cs_registers_i.mscratchcsw_in_wb ),
.csr_mscratchcsw_in_wb_i ( 1'b0 /* Not implemented in cv32e40x */ ),
.csr_mscratchcswl_in_wb_i ( core_i.cs_registers_i.mscratchcswl_in_wb ),
.csr_mnxti_in_wb_i ( core_i.cs_registers_i.mnxti_in_wb ),

Expand Down Expand Up @@ -682,9 +682,9 @@ endgenerate
.csr_mintthresh_n_i ( core_i.cs_registers_i.mintthresh_n ),
.csr_mintthresh_q_i ( core_i.cs_registers_i.mintthresh_rdata ),
.csr_mintthresh_we_i ( core_i.cs_registers_i.mintthresh_we ),
.csr_mscratchcsw_n_i ( core_i.cs_registers_i.mscratchcsw_n ),
.csr_mscratchcsw_q_i ( core_i.cs_registers_i.mscratchcsw_rdata ),
.csr_mscratchcsw_we_i ( core_i.cs_registers_i.mscratchcsw_we ),
.csr_mscratchcsw_n_i ( 32'd0 /* Not implemented in cv32e40x */ ),
.csr_mscratchcsw_q_i ( 32'd0 /* Not implemented in cv32e40x */ ),
.csr_mscratchcsw_we_i ( 1'b0 /* Not implemented in cv32e40x */ ),
.csr_mscratchcswl_n_i ( core_i.cs_registers_i.mscratchcswl_n ),
.csr_mscratchcswl_q_i ( core_i.cs_registers_i.mscratchcswl_rdata ),
.csr_mscratchcswl_we_i ( core_i.cs_registers_i.mscratchcswl_we ),
Expand Down
2 changes: 1 addition & 1 deletion rtl/cv32e40x_controller_bypass.sv
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Expand Up @@ -260,7 +260,7 @@ module cv32e40x_controller_bypass import cv32e40x_pkg::*;
// 2: or an explicit CSR read is in EX while any implicit write is in WB (conservative stall)
// 3: or an explicit CSR read is in EX while an explicit CSR write to the same CSR is in WB. (exact stall)
//
// Cases like accesses to mscratchcsw[l] and mnxti which reads multiple CSRs are handled by 1 above.
// Cases like accesses to mscratchcswl and mnxti which reads multiple CSRs are handled by 1 above.
if ((csr_hz_i.impl_re_ex && csr_write_in_wb) ||
(id_ex_pipe_i.csr_en && id_ex_pipe_i.instr_valid && csr_impl_write_in_wb) ||
csr_expl_hz_ex) begin
Expand Down
57 changes: 3 additions & 54 deletions rtl/cv32e40x_cs_registers.sv
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Expand Up @@ -216,9 +216,6 @@ module cv32e40x_cs_registers import cv32e40x_pkg::*;
logic [31:0] mintthresh_q, mintthresh_n, mintthresh_rdata;
logic mintthresh_we;

logic [31:0] mscratchcsw_n, mscratchcsw_rdata;
logic mscratchcsw_we;

logic [31:0] mscratchcswl_n, mscratchcswl_rdata;
logic mscratchcswl_we;

Expand Down Expand Up @@ -277,7 +274,6 @@ module cv32e40x_cs_registers import cv32e40x_pkg::*;
logic [31:0] mhpmcounter_write_increment; // Write increment of mhpmcounter_q

// Signal used for RVFI to set rmask, not used internally
logic mscratchcsw_in_wb;
logic mscratchcswl_in_wb;
logic mnxti_in_wb;

Expand Down Expand Up @@ -458,29 +454,6 @@ module cv32e40x_cs_registers import cv32e40x_pkg::*;
end
end

// mscratchcsw: Scratch Swap for Multiple Privilege Modes
CSR_MSCRATCHCSW: begin
if (CLIC) begin
// CLIC spec 13.2
// Depending on mstatus.MPP, we return either mscratch_rdata or rs1 to rd.
// Safe to use mstatus_rdata here (EX timing), as there is a generic stall of the ID stage
// whenever a CSR instruction follows another CSR instruction. Alternative implementation using
// a local forward of mstatus_rdata is identical (SEC).
csr_hz_o.impl_re_ex = 1'b1; // Reads mstatus and mscratch
csr_hz_o.impl_wr_ex = 1'b1; // Writes mscratch
if (mstatus_rdata.mpp != PRIV_LVL_M) begin
// Return mscratch for writing to GPR
csr_rdata_int = mscratch_rdata;
end else begin
// return rs1 for writing to GPR
csr_rdata_int = id_ex_pipe_i.alu_operand_a;
end
end else begin
csr_rdata_int = '0;
illegal_csr_read = 1'b1;
end
end

// mscratchcswl: Scratch Swap for Interrupt Levels
CSR_MSCRATCHCSWL: begin
if (CLIC) begin
Expand Down Expand Up @@ -750,10 +723,7 @@ module cv32e40x_cs_registers import cv32e40x_pkg::*;
mintthresh_n = csr_next_value(csr_wdata_int, CSR_MINTTHRESH_MASK, MINTTHRESH_RESET_VAL);
mintthresh_we = 1'b0;

mscratchcsw_n = mscratch_n; // mscratchcsw operates conditionally on mscratch
mscratchcsw_we = 1'b0;

mscratchcswl_n = mscratch_n; // mscratchcsw operates conditionally on mscratch
mscratchcswl_n = mscratch_n; // mscratchcswl operates conditionally on mscratch
mscratchcswl_we = 1'b0;

mie_n = '0;
Expand Down Expand Up @@ -795,9 +765,6 @@ module cv32e40x_cs_registers import cv32e40x_pkg::*;
mintthresh_n = '0;
mintthresh_we = 1'b0;

mscratchcsw_n = '0;
mscratchcsw_we = 1'b0;

mscratchcswl_n = '0;
mscratchcswl_we = 1'b0;

Expand Down Expand Up @@ -939,17 +906,6 @@ module cv32e40x_cs_registers import cv32e40x_pkg::*;
end
end

CSR_MSCRATCHCSW: begin
if (CLIC) begin
// mscratchcsw operates on mscratch
// Writing only when mstatus.mpp != PRIV_LVL_M
if (mstatus_rdata.mpp != PRIV_LVL_M) begin
mscratchcsw_we = 1'b1;
mscratch_we = 1'b1;
end
end
end

CSR_MSCRATCHCSWL: begin
if (CLIC) begin
// mscratchcswl operates on mscratch
Expand Down Expand Up @@ -1521,11 +1477,6 @@ dcsr_we = 1'b1;
// if no interrupt is pending.
assign mnxti_rdata = mnxti_irq_pending_i ? {mtvt_addr_o, mnxti_irq_id, 2'b00} : 32'h00000000;

// mscratchcsw_rdata breaks the regular convension for CSRs. Read data depends on mstatus.mpp
// mscratch_rdata is returned if mstatus.mpp differs from PRIV_LVL_M, otherwise rs1 is returned.
// This signal is only used by RVFI, and has WB timing (rs1 comes from ex_wb_pipe_i.csr_wdata, flopped version of id_ex_pipe.alu_operand_a)
assign mscratchcsw_rdata = (mstatus_rdata.mpp != PRIV_LVL_M) ? mscratch_rdata : ex_wb_pipe_i.csr_wdata;

// mscratchcswl_rdata breaks the regular convension for CSrs. Read data depend on mcause.pil and mintstatus.mil.
// This signal is only used by RVFI, and has WB timing (rs1 comes from ex_wb_pipe_i.csr_wdata, flopped version of id_ex_pipe.alu_operand_a)
assign mscratchcswl_rdata = ((mcause_rdata.mpil == '0) != (mintstatus_rdata.mil == 0)) ? mscratch_rdata : ex_wb_pipe_i.csr_wdata;
Expand Down Expand Up @@ -1948,16 +1899,14 @@ dcsr_we = 1'b1;
assign mcountinhibit_rdata = mcountinhibit_q;

// Assign values used for setting rmask in RVFI
assign mscratchcsw_in_wb = ex_wb_pipe_i.csr_en && (csr_waddr == CSR_MSCRATCHCSW);
assign mscratchcswl_in_wb = ex_wb_pipe_i.csr_en && (csr_waddr == CSR_MSCRATCHCSWL);
assign mnxti_in_wb = ex_wb_pipe_i.csr_en && (csr_waddr == CSR_MNXTI);

// Some signals are unused on purpose (typically they are used by RVFI code). Use them here for easier LINT waiving.

assign unused_signals = mstatush_we | misa_we | mip_we | mvendorid_we |
marchid_we | mimpid_we | mhartid_we | mconfigptr_we | mtval_we | (|mnxti_n) | mscratchcsw_we | mscratchcswl_we |
(|mscratchcsw_rdata) | (|mscratchcswl_rdata) | (|mscratchcsw_n) | (|mscratchcswl_n) |
mscratchcsw_in_wb | mscratchcswl_in_wb | mnxti_in_wb |
marchid_we | mimpid_we | mhartid_we | mconfigptr_we | mtval_we | (|mnxti_n) | mscratchcswl_we |
(|mscratchcswl_rdata) | (|mscratchcswl_n) |mscratchcswl_in_wb | mnxti_in_wb |
(|mtval_n) | (|mconfigptr_n) | (|mhartid_n) | (|mimpid_n) | (|marchid_n) | (|mvendorid_n) | (|mip_n) | (|misa_n) | (|mstatush_n);

endmodule
4 changes: 2 additions & 2 deletions rtl/cv32e40x_i_decoder.sv
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Expand Up @@ -379,8 +379,8 @@ module cv32e40x_i_decoder import cv32e40x_pkg::*;
endcase

if (CLIC) begin
// The mscratchcsw[l] CSRs are only accessible using CSRRW with neither rd nor rs1 set to x0
if ((instr_rdata_i[31:20] == CSR_MSCRATCHCSW) || (instr_rdata_i[31:20] == CSR_MSCRATCHCSWL)) begin
// The mscratchcswl CSR is only accessible using CSRRW with neither rd nor rs1 set to x0
if (instr_rdata_i[31:20] == CSR_MSCRATCHCSWL) begin
if (instr_rdata_i[14:12] == 3'b001) begin // CSRRW
if ((instr_rdata_i[11:7] == 5'b0) || (instr_rdata_i[19:15] == 5'b0)) begin
// rd or rs1 is zero, flag instruction as illegal
Expand Down
1 change: 0 additions & 1 deletion rtl/include/cv32e40x_pkg.sv
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Expand Up @@ -263,7 +263,6 @@ typedef enum logic[11:0] {
CSR_MIP = 12'h344,
CSR_MNXTI = 12'h345,
CSR_MINTTHRESH = 12'h347,
CSR_MSCRATCHCSW = 12'h348,
CSR_MSCRATCHCSWL = 12'h349,
CSR_MCLICBASE = 12'h34A,

Expand Down
10 changes: 0 additions & 10 deletions sva/cv32e40x_cs_registers_sva.sv
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Expand Up @@ -119,16 +119,6 @@ module cv32e40x_cs_registers_sva
a_htrap_interrupt_level: assert property(p_htrap_interrupt_level)
else `uvm_error("cs_registers", "Horizontal trap taken caused interrupt level to change");

// Check that mscratch do not update due to mscratchcsw if the conditions are not right
property p_mscratchcsw_mscratch;
@(posedge clk) disable iff (!rst_n)
( ex_wb_pipe_i.csr_en && (csr_waddr == CSR_MSCRATCHCSW) && (mstatus_q.mpp == PRIV_LVL_M)
|=> $stable(mscratch_q));
endproperty;

a_mscratchcsw_mscratch: assert property(p_mscratchcsw_mscratch)
else `uvm_error("cs_registers", "Mscratch not stable after mscratwchsw with mpp=M");

// Check that mscratch do not update due to mscratchcswl if the conditions are not right
property p_mscratchcswl_mscratch;
@(posedge clk) disable iff (!rst_n)
Expand Down
2 changes: 1 addition & 1 deletion yaml/csr.yaml.m4
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Expand Up @@ -4487,7 +4487,7 @@ ifelse(eval(CLIC != 0), 1, [[[
lsb: 0
]]])
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Not okay to remove this from the yaml file as we try to have the same yaml between 40x and 40s. The CSR should be excluded for non-CLIC and if user mode is not supported.

Only this file should get merged to the 40S, not the other files

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Added mscratchcsw back in and guarded with CLIC and UMODE.


ifelse(eval(CLIC != 0), 1, [[[
ifelse(eval((CLIC != 0) && (UMODE != 0)), 1, [[[
- csr: mscratchcsw
description: >
Machine scratch swap for privilege mode change
Expand Down