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🐛 Fix wrong interrupt stack behaviour
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@zarubaf
zarubaf committed Nov 3, 2018
1 parent 1b1b4a4 commit ab2d590
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Showing 2 changed files with 74 additions and 52 deletions.
36 changes: 19 additions & 17 deletions include/ariane_pkg.sv
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Original file line number Diff line number Diff line change
Expand Up @@ -68,23 +68,25 @@ package ariane_pkg;
localparam logic INVALIDATE_ON_FLUSH = 1'b1;

// read mask for SSTATUS over MMSTATUS
localparam logic [63:0] SMODE_STATUS_MASK = riscv::SSTATUS_UIE
| riscv::SSTATUS_SIE
| riscv::SSTATUS_SPIE
| riscv::SSTATUS_SPP
| riscv::SSTATUS_FS
| riscv::SSTATUS_XS
| riscv::SSTATUS_SUM
| riscv::SSTATUS_MXR
| riscv::SSTATUS_UPIE
| riscv::SSTATUS_SPIE
| riscv::SSTATUS_SPP
| riscv::SSTATUS_FS
| riscv::SSTATUS_XS
| riscv::SSTATUS_SUM
| riscv::SSTATUS_MXR
| riscv::SSTATUS_UXL
| riscv::SSTATUS64_SD;
localparam logic [63:0] SMODE_STATUS_READ_MASK = riscv::SSTATUS_UIE
| riscv::SSTATUS_SIE
| riscv::SSTATUS_SPIE
| riscv::SSTATUS_SPP
| riscv::SSTATUS_FS
| riscv::SSTATUS_XS
| riscv::SSTATUS_SUM
| riscv::SSTATUS_MXR
| riscv::SSTATUS_UPIE
| riscv::SSTATUS_SPIE
| riscv::SSTATUS_UXL
| riscv::SSTATUS64_SD;

localparam logic [63:0] SMODE_STATUS_WRITE_MASK = riscv::SSTATUS_SIE
| riscv::SSTATUS_SPIE
| riscv::SSTATUS_SPP
| riscv::SSTATUS_FS
| riscv::SSTATUS_SUM
| riscv::SSTATUS_MXR;
// ---------------
// Fetch Stage
// ---------------
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90 changes: 55 additions & 35 deletions src/csr_regfile.sv
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ import ariane_pkg::*;
module csr_regfile #(
parameter int ASID_WIDTH = 1,
parameter int unsigned NR_COMMIT_PORTS = 2
)(
) (
input logic clk_i, // Clock
input logic rst_ni, // Asynchronous reset active low
input logic time_irq_i, // Timer threw a interrupt
Expand Down Expand Up @@ -156,7 +156,9 @@ module csr_regfile #(
riscv::CSR_TDATA2:; // not implemented
riscv::CSR_TDATA3:; // not implemented
// supervisor registers
riscv::CSR_SSTATUS: csr_rdata = mstatus_q & ariane_pkg::SMODE_STATUS_MASK;
riscv::CSR_SSTATUS: begin
csr_rdata = mstatus_q & ariane_pkg::SMODE_STATUS_READ_MASK;
end
riscv::CSR_SIE: csr_rdata = mie_q & mideleg_q;
riscv::CSR_SIP: csr_rdata = mip_q & mideleg_q;
riscv::CSR_STVEC: csr_rdata = stvec_q;
Expand Down Expand Up @@ -312,24 +314,8 @@ module csr_regfile #(
riscv::CSR_TDATA3:; // not implemented
// sstatus is a subset of mstatus - mask it accordingly
riscv::CSR_SSTATUS: begin
mstatus_d = csr_wdata;
// also hardwire the registers for sstatus
mstatus_d.sxl = riscv::XLEN_64;
mstatus_d.uxl = riscv::XLEN_64;
// hardwired zero registers
mstatus_d.sd = 1'b0;
mstatus_d.xs = 2'b0;
mstatus_d.fs = 2'b0;
mstatus_d.upie = 1'b0;
mstatus_d.uie = 1'b0;
// not all fields of mstatus can be written
mstatus_d.mie = mstatus_q.mie;
mstatus_d.mpie = mstatus_q.mpie;
mstatus_d.mpp = mstatus_q.mpp;
mstatus_d.mprv = mstatus_q.mprv;
mstatus_d.tsr = mstatus_q.tsr;
mstatus_d.tw = mstatus_q.tw;
mstatus_d.tvm = mstatus_q.tvm;
mask = ariane_pkg::SMODE_STATUS_WRITE_MASK;
mstatus_d = (mstatus_q & ~mask) | (csr_wdata & mask);
// this instruction has side-effects
flush_o = 1'b1;
end
Expand Down Expand Up @@ -453,8 +439,6 @@ module csr_regfile #(
// ---------------------
// Machine Mode External Interrupt Pending
mip_d[riscv::IRQ_M_EXT] = irq_i[0];
// Supervisor Mode External Interrupt Pending
mip_d[riscv::IRQ_S_EXT] = mie_q[riscv::IRQ_S_EXT];
// Machine software interrupt
mip_d[riscv::IRQ_M_SOFT] = ipi_i;
// Timer interrupt pending, coming from platform timer
Expand Down Expand Up @@ -488,7 +472,7 @@ module csr_regfile #(
mstatus_d.sie = 1'b0;
mstatus_d.spie = mstatus_q.sie;
// this can either be user or supervisor mode
mstatus_d.spp = logic'(priv_lvl_q);
mstatus_d.spp = priv_lvl_q[0];
// set cause
scause_d = ex_i.cause;
// set epc
Expand All @@ -510,7 +494,6 @@ module csr_regfile #(
end

priv_lvl_d = trap_to_priv_lvl;

end

// ------------------------------
Expand Down Expand Up @@ -623,11 +606,11 @@ module csr_regfile #(
// return from exception, IF doesn't care from where we are returning
eret_o = 1'b1;
// return the previous supervisor interrupt enable flag
mstatus_d.sie = mstatus_d.spie;
mstatus_d.sie = mstatus_q.spie;
// restore the previous privilege level
priv_lvl_d = riscv::priv_lvl_t'({1'b0, mstatus_d.spp});
priv_lvl_d = riscv::priv_lvl_t'({1'b0, mstatus_q.spp});
// set spp to user mode
mstatus_d.spp = logic'(riscv::PRIV_LVL_U);
mstatus_d.spp = 1'b0;
// set spie to 1
mstatus_d.spie = 1'b1;
end
Expand Down Expand Up @@ -783,9 +766,10 @@ module csr_regfile #(
// -------------------
// if there is any interrupt pending un-stall the core
// also un-stall if we want to enter debug mode
if (|mip_q || debug_req_i) begin
if (|mip_q || debug_req_i || irq_i[1]) begin
wfi_d = 1'b0;
// or alternatively if there is no exception pending and we are not in debug mode wait here for the interrupt
// or alternatively if there is no exception pending and we are not in debug mode wait here
// for the interrupt
end else if (!debug_mode_q && csr_op_i == WFI && !ex_i.valid) begin
wfi_d = 1'b1;
end
Expand Down Expand Up @@ -822,22 +806,58 @@ module csr_regfile #(
end
end

ila_0 i_ila_0 (
.clk(clk_i), // input wire clk
.probe0(commit_instr_i[0].pc), // input wire [63:0] probe0
.probe1(commit_instr_i[1].pc), // input wire [63:0] probe1
.probe2(commit_ack_i[0]), // input wire [0:0] probe2
.probe3(commit_ack_i[1]), // input wire [0:0] probe3
.probe4(mstatus_q.mie), // input wire [0:0] probe4
.probe5(mstatus_q.mpp), // input wire [1:0] probe5
.probe6(mstatus_q.mpie), // input wire [0:0] probe6
.probe7(mstatus_q.sie), // input wire [0:0] probe7
.probe8(mstatus_q.spp), // input wire [0:0] probe8
.probe9(mstatus_q.spie), // input wire [0:0] probe9
.probe10(mip_q[riscv::IRQ_S_SOFT]), // input wire [0:0] probe10
.probe11(mip_q[riscv::IRQ_M_SOFT]), // input wire [0:0] probe11
.probe12(mip_q[riscv::IRQ_S_TIMER]), // input wire [0:0] probe12
.probe13(mip_q[riscv::IRQ_M_TIMER]), // input wire [0:0] probe13
.probe14(mie_q[riscv::IRQ_S_SOFT]), // input wire [0:0] probe14
.probe15(mie_q[riscv::IRQ_M_SOFT]), // input wire [0:0] probe15
.probe16(mie_q[riscv::IRQ_S_TIMER]), // input wire [0:0] probe16
.probe17(mie_q[riscv::IRQ_M_TIMER]), // input wire [0:0] probe17
.probe18(priv_lvl_o) // input wire [1:0] probe18
);

// -------------------
// Output Assignments
// -------------------
// When the SEIP bit is read with a CSRRW, CSRRS, or CSRRC instruction, the value
// returned in the rd destination register contains the logical-OR of the software-writable
// bit and the interrupt signal from the interrupt controller.
assign csr_rdata_o = (csr_addr.address == riscv::CSR_MIP) ? (csr_rdata | (irq_i[1] << riscv::IRQ_S_EXT))
: csr_rdata;
always_comb begin
// When the SEIP bit is read with a CSRRW, CSRRS, or CSRRC instruction, the value
// returned in the rd destination register contains the logical-OR of the software-writable
// bit and the interrupt signal from the interrupt controller.
csr_rdata_o = csr_rdata;

unique case (csr_addr.address)
riscv::CSR_MIP: csr_rdata_o = csr_rdata | (irq_i[1] << riscv::IRQ_S_EXT);
// in supervisor mode we also need to check whether we delegated this bit
riscv::CSR_SIP: begin
csr_rdata_o = csr_rdata
| ((irq_i[1] & mideleg_q[riscv::IRQ_S_EXT]) << riscv::IRQ_S_EXT);
end
default:;
endcase
end
// in debug mode we execute with privilege level M
assign priv_lvl_o = (debug_mode_q) ? riscv::PRIV_LVL_M : priv_lvl_q;
// MMU outputs
assign satp_ppn_o = satp_q.ppn;
assign asid_o = satp_q.asid[ASID_WIDTH-1:0];
assign sum_o = mstatus_q.sum;
// we support bare memory addressing and SV39
assign en_translation_o = (satp_q.mode == 4'h8 && priv_lvl_o != riscv::PRIV_LVL_M) ? 1'b1 : 1'b0;
assign en_translation_o = (satp_q.mode == 4'h8 && priv_lvl_o != riscv::PRIV_LVL_M)
? 1'b1
: 1'b0;
assign mxr_o = mstatus_q.mxr;
assign tvm_o = mstatus_q.tvm;
assign tw_o = mstatus_q.tw;
Expand Down

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