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remedy endless feedback loop #102

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remedy endless feedback loop #102

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8953fe2
remedy endless feedback loop
majbthrd Dec 13, 2020
4a3b786
alternate remedy for endless feedback loop
majbthrd Feb 28, 2021
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16 changes: 11 additions & 5 deletions src/dm_mem.sv
100755 → 100644
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Original file line number Diff line number Diff line change
Expand Up @@ -137,13 +137,12 @@ module dm_mem #(
cmderror_valid_o = 1'b0;
cmderror_o = dm::CmdErrNone;
state_d = state_q;
go = 1'b0;
resume = 1'b0;
cmdbusy_o = 1'b1;

unique case (state_q)
Idle: begin
cmdbusy_o = 1'b0;
go = 1'b0;
resume = 1'b0;
if (cmd_valid_i && halted_q_aligned[hartsel] && !unsupported_command) begin
// give the go signal
state_d = Go;
Expand All @@ -164,6 +163,7 @@ module dm_mem #(
// we are already busy here since we scheduled the execution of a program
cmdbusy_o = 1'b1;
go = 1'b1;
resume = 1'b0;
// the thread is now executing the command, track its state
if (going) begin
state_d = CmdExecuting;
Expand All @@ -172,7 +172,8 @@ module dm_mem #(

Resume: begin
cmdbusy_o = 1'b1;
resume = 1'b1;
go = 1'b0;
resume = 1'b1;
if (resuming_q_aligned[hartsel]) begin
state_d = Idle;
end
Expand All @@ -181,13 +182,18 @@ module dm_mem #(
CmdExecuting: begin
cmdbusy_o = 1'b1;
go = 1'b0;
resume = 1'b0;
// wait until the hart has halted again
if (halted_aligned[hartsel]) begin
state_d = Idle;
end
end

default: ;
default: begin
cmdbusy_o = 1'b1;
go = 1'b0;
resume = 1'b0;
end
endcase

// only signal once that cmd is unsupported so that we can clear cmderr
Expand Down