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[control] minor cleanups
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@stnolting
stnolting committed Jan 11, 2025
1 parent 99ab672 commit 6dc0206
Showing 1 changed file with 37 additions and 38 deletions.
75 changes: 37 additions & 38 deletions rtl/core/neorv32_cpu_control.vhd
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Original file line number Diff line number Diff line change
Expand Up @@ -226,8 +226,8 @@ architecture neorv32_cpu_control_rtl of neorv32_cpu_control is
mie_mti : std_ulogic; -- machine timer interrupt enable
mie_firq : std_ulogic_vector(15 downto 0); -- fast interrupt enable
--
privilege : std_ulogic; -- current privilege mode
privilege_eff : std_ulogic; -- current *effective* privilege mode
prv_level : std_ulogic; -- current privilege level
prv_level_eff : std_ulogic; -- current *effective* privilege level
--
mepc : std_ulogic_vector(XLEN-1 downto 0); -- machine exception PC
mcause : std_ulogic_vector(5 downto 0); -- machine trap cause
Expand Down Expand Up @@ -339,7 +339,7 @@ begin
-- ------------------------------------------------------------
fetch_engine.restart <= '0'; -- restart done
fetch_engine.pc <= exe_engine.pc2(XLEN-1 downto 1) & '0'; -- initialize from PC incl. 16-bit-alignment bit
fetch_engine.priv <= csr.privilege_eff; -- set new privilege level
fetch_engine.priv <= csr.prv_level_eff; -- set new privilege level
fetch_engine.state <= IF_REQUEST;

end case;
Expand Down Expand Up @@ -874,13 +874,13 @@ begin
ctrl_o.lsu_rw <= ctrl.lsu_rw;
ctrl_o.lsu_mo_we <= '1' when (exe_engine.state = EX_MEM_REQ) else '0'; -- write memory output registers (data & address)
ctrl_o.lsu_fence <= ctrl.lsu_fence;
ctrl_o.lsu_priv <= csr.mstatus_mpp when (csr.mstatus_mprv = '1') else csr.privilege_eff; -- effective privilege level for loads/stores in M-mode
ctrl_o.lsu_priv <= csr.mstatus_mpp when (csr.mstatus_mprv = '1') else csr.prv_level_eff; -- effective privilege level for loads/stores in M-mode
-- instruction word bit fields --
ctrl_o.ir_funct3 <= exe_engine.ir(instr_funct3_msb_c downto instr_funct3_lsb_c);
ctrl_o.ir_funct12 <= exe_engine.ir(instr_funct12_msb_c downto instr_funct12_lsb_c);
ctrl_o.ir_opcode <= opcode;
-- cpu status --
ctrl_o.cpu_priv <= csr.privilege_eff;
ctrl_o.cpu_priv <= csr.prv_level_eff;
ctrl_o.cpu_sleep <= sleep_mode;
ctrl_o.cpu_trap <= trap_ctrl.env_enter;
ctrl_o.cpu_debug <= debug_ctrl.run;
Expand Down Expand Up @@ -997,12 +997,12 @@ begin
if (csr_addr_v(11 downto 4) = csr_dcsr_c(11 downto 4)) and -- debug-mode-only CSR?
RISCV_ISA_Sdext and (debug_ctrl.run = '0') then -- debug-mode implemented and not running?
csr_valid(0) <= '0'; -- invalid access
elsif RISCV_ISA_Zicntr and RISCV_ISA_U and (csr.privilege_eff = '0') and -- any user-mode counters available and in user-mode?
elsif RISCV_ISA_Zicntr and RISCV_ISA_U and (csr.prv_level_eff = '0') and -- any user-mode counters available and in user-mode?
(csr_addr_v(11 downto 8) = csr_cycle_c(11 downto 8)) and -- user-mode counter access
(((csr_addr_v(1 downto 0) = csr_cycle_c(1 downto 0)) and (csr.mcounteren_cy = '0')) or -- illegal access to cycle
((csr_addr_v(1 downto 0) = csr_instret_c(1 downto 0)) and (csr.mcounteren_ir = '0'))) then -- illegal access to instret
csr_valid(0) <= '0'; -- invalid access
elsif (csr_addr_v(9 downto 8) /= "00") and (csr.privilege_eff = '0') then -- invalid privilege level
elsif (csr_addr_v(9 downto 8) /= "00") and (csr.prv_level_eff = '0') then -- invalid privilege level
csr_valid(0) <= '0'; -- invalid access
else
csr_valid(0) <= '1'; -- access granted
Expand Down Expand Up @@ -1066,9 +1066,9 @@ begin
case exe_engine.ir(instr_funct12_msb_c downto instr_funct12_lsb_c) is
when funct12_ecall_c => illegal_cmd <= '0'; -- ecall is always allowed
when funct12_ebreak_c => illegal_cmd <= '0'; -- ebreak is always allowed
when funct12_mret_c => illegal_cmd <= (not csr.privilege) or debug_ctrl.run; -- mret allowed in (real/non-debug) M-mode only
when funct12_mret_c => illegal_cmd <= (not csr.prv_level) or debug_ctrl.run; -- mret allowed in (real/non-debug) M-mode only
when funct12_dret_c => illegal_cmd <= not debug_ctrl.run; -- dret allowed in debug mode only
when funct12_wfi_c => illegal_cmd <= (not csr.privilege) and csr.mstatus_tw; -- wfi allowed in M-mode or if TW is zero
when funct12_wfi_c => illegal_cmd <= (not csr.prv_level) and csr.mstatus_tw; -- wfi allowed in M-mode or if TW is zero
when others => illegal_cmd <= '1'; -- undefined
end case;
end if;
Expand Down Expand Up @@ -1126,8 +1126,8 @@ begin
if RISCV_ISA_Sdext then
trap_ctrl.exc_buf(exc_ebreak_c) <= (not trap_ctrl.env_enter) and (trap_ctrl.exc_buf(exc_ebreak_c) or
(trap_ctrl.hwtrig and (not csr.tdata1_action)) or -- trigger module fires and enter-debug-action is disabled
(trap_ctrl.ebreak and ( csr.privilege) and (not csr.dcsr_ebreakm) and (not debug_ctrl.run)) or -- enter M-mode handler on ebreak in M-mode
(trap_ctrl.ebreak and (not csr.privilege) and (not csr.dcsr_ebreaku) and (not debug_ctrl.run))); -- enter M-mode handler on ebreak in U-mode
(trap_ctrl.ebreak and ( csr.prv_level) and (not csr.dcsr_ebreakm) and (not debug_ctrl.run)) or -- enter M-mode handler on ebreak in M-mode
(trap_ctrl.ebreak and (not csr.prv_level) and (not csr.dcsr_ebreaku) and (not debug_ctrl.run))); -- enter M-mode handler on ebreak in U-mode
else
trap_ctrl.exc_buf(exc_ebreak_c) <= (trap_ctrl.exc_buf(exc_ebreak_c) or trap_ctrl.ebreak or (trap_ctrl.hwtrig and (not csr.tdata1_action))) and (not trap_ctrl.env_enter);
end if;
Expand Down Expand Up @@ -1200,7 +1200,7 @@ begin
if (trap_ctrl.exc_buf(exc_iaccess_c) = '1') then trap_ctrl.cause <= trap_iaf_c; -- instruction access fault
elsif (trap_ctrl.exc_buf(exc_illegal_c) = '1') then trap_ctrl.cause <= trap_iil_c; -- illegal instruction
elsif (trap_ctrl.exc_buf(exc_ialign_c) = '1') then trap_ctrl.cause <= trap_ima_c; -- instruction address misaligned
elsif (trap_ctrl.exc_buf(exc_ecall_c) = '1') then trap_ctrl.cause <= trap_env_c(6 downto 2) & replicate_f(csr.privilege, 2); -- environment call (U/M)
elsif (trap_ctrl.exc_buf(exc_ecall_c) = '1') then trap_ctrl.cause <= trap_env_c(6 downto 2) & replicate_f(csr.prv_level, 2); -- environment call (U/M)
elsif (trap_ctrl.exc_buf(exc_ebreak_c) = '1') then trap_ctrl.cause <= trap_brk_c; -- environment breakpoint
elsif (trap_ctrl.exc_buf(exc_salign_c) = '1') then trap_ctrl.cause <= trap_sma_c; -- store address misaligned
elsif (trap_ctrl.exc_buf(exc_lalign_c) = '1') then trap_ctrl.cause <= trap_lma_c; -- load address misaligned
Expand Down Expand Up @@ -1274,7 +1274,7 @@ begin
trap_ctrl.irq_fire(0) <= '1' when
(exe_engine.state = EX_EXECUTE) and -- trigger system IRQ only in EX_EXECUTE state
(or_reduce_f(trap_ctrl.irq_buf(irq_firq_15_c downto irq_msi_irq_c)) = '1') and -- pending system IRQ
((csr.mstatus_mie = '1') or (csr.privilege = priv_mode_u_c)) and -- IRQ only when in M-mode and MIE=1 OR when in U-mode
((csr.mstatus_mie = '1') or (csr.prv_level = priv_mode_u_c)) and -- IRQ only when in M-mode and MIE=1 OR when in U-mode
(debug_ctrl.run = '0') and (csr.dcsr_step = '0') else '0'; -- no system IRQs when in debug-mode / during single-stepping

-- debug-entry halt interrupt? --
Expand Down Expand Up @@ -1353,7 +1353,7 @@ begin
begin
if (rstn_i = '0') then
csr.we <= '0';
csr.privilege <= priv_mode_m_c;
csr.prv_level <= priv_mode_m_c;
csr.mstatus_mie <= '0';
csr.mstatus_mpie <= '0';
csr.mstatus_mpp <= priv_mode_m_c;
Expand All @@ -1364,8 +1364,8 @@ begin
csr.mie_mti <= '0';
csr.mie_firq <= (others => '0');
csr.mtvec <= (others => '0');
csr.mscratch <= x"19880704";
csr.mepc <= BOOT_ADDR(XLEN-1 downto 2) & "00"; -- 32-bit-aligned boot address
csr.mscratch <= (others => '0');
csr.mepc <= (others => '0');
csr.mcause <= (others => '0');
csr.mtval <= (others => '0');
csr.mtinst <= (others => '0');
Expand Down Expand Up @@ -1538,16 +1538,16 @@ begin
csr.mtinst <= (others => '0');
end if;
-- update privilege level and interrupt-enable stack --
csr.privilege <= priv_mode_m_c; -- execute trap in machine mode
csr.prv_level <= priv_mode_m_c; -- execute trap in machine mode
csr.mstatus_mie <= '0'; -- disable interrupts
csr.mstatus_mpie <= csr.mstatus_mie; -- backup previous mie state
csr.mstatus_mpp <= csr.privilege; -- backup previous privilege mode
csr.mstatus_mpp <= csr.prv_level; -- backup previous privilege level
end if;

-- DEBUG trap entry - no CSR update when already in debug-mode! --
if RISCV_ISA_Sdext and (trap_ctrl.cause(5) = '1') and (debug_ctrl.run = '0') then
csr.dcsr_cause <= trap_ctrl.cause(2 downto 0); -- trap cause
csr.dcsr_prv <= csr.privilege; -- current privilege mode when debug mode was entered
csr.dcsr_prv <= csr.prv_level; -- current privilege level when debug mode was entered
csr.dpc <= trap_ctrl.epc(XLEN-1 downto 1) & '0'; -- trap PC
end if;

Expand All @@ -1559,18 +1559,18 @@ begin
-- return from debug mode --
if RISCV_ISA_Sdext and (debug_ctrl.run = '1') then
if RISCV_ISA_U then
csr.privilege <= csr.dcsr_prv;
csr.prv_level <= csr.dcsr_prv;
if (csr.dcsr_prv /= priv_mode_m_c) then
csr.mstatus_mprv <= '0'; -- clear if return to priv. mode less than M
csr.mstatus_mprv <= '0'; -- clear if return to priv. level less than M
end if;
end if;
-- return from normal trap --
else
if RISCV_ISA_U then
csr.privilege <= csr.mstatus_mpp; -- restore previous privilege mode
csr.mstatus_mpp <= priv_mode_u_c; -- set to least-privileged mode that is supported
csr.prv_level <= csr.mstatus_mpp; -- restore previous privilege level
csr.mstatus_mpp <= priv_mode_u_c; -- set to least-privileged level that is supported
if (csr.mstatus_mpp /= priv_mode_m_c) then
csr.mstatus_mprv <= '0'; -- clear if return to priv. mode less than M
csr.mstatus_mprv <= '0'; -- clear if return to priv. level less than M
end if;
end if;
csr.mstatus_mie <= csr.mstatus_mpie; -- restore machine-mode IRQ enable flag
Expand Down Expand Up @@ -1604,7 +1604,7 @@ begin

-- no user mode --
if not RISCV_ISA_U then
csr.privilege <= priv_mode_m_c;
csr.prv_level <= priv_mode_m_c;
csr.mstatus_mpp <= priv_mode_m_c;
csr.mstatus_mprv <= '0';
csr.mstatus_tw <= '0';
Expand Down Expand Up @@ -1636,8 +1636,8 @@ begin
end if;
end process csr_write_access;

-- effective privilege mode is MACHINE when in debug mode --
csr.privilege_eff <= priv_mode_m_c when (debug_ctrl.run = '1') else csr.privilege;
-- effective privilege level is MACHINE when in debug mode --
csr.prv_level_eff <= priv_mode_m_c when (debug_ctrl.run = '1') else csr.prv_level;


-- CSR Read Access ------------------------------------------------------------------------
Expand Down Expand Up @@ -1688,13 +1688,13 @@ begin
-- when csr_mstatush_c => csr.rdata <= (others => '0'); -- machine status register, high word - hardwired to zero

when csr_misa_c => -- ISA and extensions
csr.rdata(1) <= bool_to_ulogic_f(RISCV_ISA_B); -- B CPU extension
csr.rdata(2) <= bool_to_ulogic_f(RISCV_ISA_C); -- C CPU extension
csr.rdata(4) <= bool_to_ulogic_f(RISCV_ISA_E); -- E CPU extension
csr.rdata(8) <= bool_to_ulogic_f(not RISCV_ISA_E); -- I CPU extension (if not E)
csr.rdata(12) <= bool_to_ulogic_f(RISCV_ISA_M); -- M CPU extension
csr.rdata(20) <= bool_to_ulogic_f(RISCV_ISA_U); -- U CPU extension
csr.rdata(23) <= '1'; -- X CPU extension (non-standard / NEORV32-specific)
csr.rdata(1) <= bool_to_ulogic_f(RISCV_ISA_B);
csr.rdata(2) <= bool_to_ulogic_f(RISCV_ISA_C);
csr.rdata(4) <= bool_to_ulogic_f(RISCV_ISA_E);
csr.rdata(8) <= bool_to_ulogic_f(not RISCV_ISA_E); -- I = not E
csr.rdata(12) <= bool_to_ulogic_f(RISCV_ISA_M);
csr.rdata(20) <= bool_to_ulogic_f(RISCV_ISA_U);
csr.rdata(23) <= '1'; -- X CPU extension (non-standard / NEORV32-specific)
csr.rdata(31 downto 30) <= "01"; -- MXL = 32

when csr_mie_c => -- machine interrupt-enable register
Expand Down Expand Up @@ -1878,7 +1878,6 @@ begin
csr.rdata(24) <= bool_to_ulogic_f(RISCV_ISA_Zbs); -- Zbs: single-bit bit-manipulation
csr.rdata(25) <= bool_to_ulogic_f(RISCV_ISA_Zaamo); -- Zaamo: atomic memory operations
csr.rdata(26) <= '0'; -- reserved
csr.rdata(27) <= '0'; -- reserved
-- tuning options --
csr.rdata(27) <= bool_to_ulogic_f(CPU_CLOCK_GATING_EN); -- enable clock gating when in sleep mode
csr.rdata(28) <= bool_to_ulogic_f(CPU_RF_HW_RST_EN); -- full hardware reset of register file
Expand Down Expand Up @@ -2076,8 +2075,8 @@ begin
-- debug mode entry triggers --
debug_ctrl.trig_hw <= trap_ctrl.hwtrig and (not debug_ctrl.run) and csr.tdata1_action and csr.tdata1_dmode; -- enter debug mode by HW trigger module
debug_ctrl.trig_break <= trap_ctrl.ebreak and (debug_ctrl.run or -- re-enter debug mode
(( csr.privilege) and csr.dcsr_ebreakm) or -- enabled goto-debug-mode in machine mode on "ebreak"
((not csr.privilege) and csr.dcsr_ebreaku)); -- enabled goto-debug-mode in user mode on "ebreak"
(( csr.prv_level) and csr.dcsr_ebreakm) or -- enabled goto-debug-mode in machine mode on "ebreak"
((not csr.prv_level) and csr.dcsr_ebreaku)); -- enabled goto-debug-mode in user mode on "ebreak"
debug_ctrl.trig_halt <= irq_dbg_i and (not debug_ctrl.run); -- external halt request (if not halted already)
debug_ctrl.trig_step <= csr.dcsr_step and (not debug_ctrl.run); -- single-step mode (trigger when NOT CURRENTLY in debug mode)

Expand Down Expand Up @@ -2110,7 +2109,7 @@ begin
csr.dcsr_rd(4) <= '1'; -- mprven: mstatus.mprv is also evaluated in debug mode
csr.dcsr_rd(3) <= '0'; -- nmip: no pending non-maskable interrupt
csr.dcsr_rd(2) <= csr.dcsr_step; -- step: single-step mode
csr.dcsr_rd(1 downto 0) <= (others => csr.dcsr_prv); -- prv: privilege mode when debug mode was entered
csr.dcsr_rd(1 downto 0) <= (others => csr.dcsr_prv); -- prv: privilege level when debug mode was entered


-- ****************************************************************************************************************************
Expand Down

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