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[rtl] Debug mode controller changes

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* `if` in `DBG_TAKEN_IF` is needless as the conditions it checks will be
  true if controller enters `DBG_TAKEN_IF` state

* flop `enter_debug_mode` so `FLUSH` state looks at what
  `enter_debug_mode` was when it was seen in `DECODE` state rather than
  what it has become. In particular the controller could enter `FLUSH`
  on the basis of performing a WFI then divert down the debug control
  path due to a new debug request being raised. In this instance it is
  preferable for the WFI to complete entering `SLEEP` before the debug
  request wakes the core back up.
This commit is contained in:
Greg Chadwick 2021-02-10 16:25:51 +00:00
parent 65287f7d7b
commit 99b8f61223
1 changed files with 39 additions and 38 deletions
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17
rtl/ibex_controller.sv
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@ -144,7 +144,8 @@ module ibex_controller #(
logic exc_req_lsu;
logic special_req_all;
logic special_req_branch;
logic enter_debug_mode;
logic enter_debug_mode_d;
logic enter_debug_mode_q;
logic ebreak_into_debug;
logic handle_irq;
@ -317,7 +318,7 @@ module ibex_controller #(
// due to a recently flushed IF (or a delay in an instruction returning from
// memory) before it has had anything to single step.
// Also enter debug mode on a trigger match (hardware breakpoint)
assign enter_debug_mode = (debug_req_i | (debug_single_step_i & instr_valid_i) |
assign enter_debug_mode_d = (debug_req_i | (debug_single_step_i & instr_valid_i) |
trigger_match_i) & ~debug_mode_q;
// Set when an ebreak should enter debug mode rather than jump to exception
@ -461,7 +462,7 @@ module ibex_controller #(
end
// enter debug mode
if (enter_debug_mode) begin
if (enter_debug_mode_d) begin
ctrl_fsm_ns = DBG_TAKEN_IF;
// Halt IF only for now, ID will be flushed in DBG_TAKEN_IF as the
// ID state is needed for correct debug mode entry
@ -530,12 +531,12 @@ module ibex_controller #(
// If entering debug mode or handling an IRQ the core needs to wait
// until the current instruction has finished executing. Stall IF
// during that time.
if ((enter_debug_mode || handle_irq) && stall) begin
if ((enter_debug_mode_d || handle_irq) && stall) begin
halt_if = 1'b1;
end
if (!stall && !special_req_all) begin
if (enter_debug_mode) begin
if (enter_debug_mode_d) begin
// enter debug mode
ctrl_fsm_ns = DBG_TAKEN_IF;
// Halt IF only for now, ID will be flushed in DBG_TAKEN_IF as the
@ -594,7 +595,6 @@ module ibex_controller #(
// enter debug mode and save PC in IF to dpc
// jump to debug exception handler in debug memory
if (debug_single_step_i || debug_req_i || trigger_match_i) begin
flush_id = 1'b1;
pc_set_o = 1'b1;
pc_set_spec_o = 1'b1;
@ -613,7 +613,6 @@ module ibex_controller #(
// enter debug mode
debug_mode_d = 1'b1;
end
ctrl_fsm_ns = DECODE;
end
@ -770,7 +769,7 @@ module ibex_controller #(
// If an EBREAK instruction is causing us to enter debug mode on the
// same cycle as a debug_req or single step, honor the EBREAK and
// proceed to DBG_TAKEN_ID.
if (enter_debug_mode && !(ebrk_insn_prio && ebreak_into_debug)) begin
if (enter_debug_mode_q && !(ebrk_insn_prio && ebreak_into_debug)) begin
ctrl_fsm_ns = DBG_TAKEN_IF;
end
end // FLUSH
@ -815,6 +814,7 @@ module ibex_controller #(
ctrl_fsm_cs <= RESET;
nmi_mode_q <= 1'b0;
debug_mode_q <= 1'b0;
enter_debug_mode_q <= 1'b0;
load_err_q <= 1'b0;
store_err_q <= 1'b0;
exc_req_q <= 1'b0;
@ -823,6 +823,7 @@ module ibex_controller #(
ctrl_fsm_cs <= ctrl_fsm_ns;
nmi_mode_q <= nmi_mode_d;
debug_mode_q <= debug_mode_d;
enter_debug_mode_q <= enter_debug_mode_d;
load_err_q <= load_err_d;
store_err_q <= store_err_d;
exc_req_q <= exc_req_d;