colin
/
Hazard3
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Change style of IRQ register tie-offs as Yosys was not able to trim them for iCE40 synthesis.

This commit is contained in:
Luke Wren 2022-09-04 23:43:24 +01:00
parent 3ae843034d
commit c594ec42e9
1 changed files with 29 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
hdl/hazard3_csr.v
View File

@ -328,8 +328,6 @@ end
// Custom external IRQ handling CSRs
localparam MAX_IRQS = 512;
localparam [MAX_IRQS-1:0] IRQ_IMPL_MASK = ~({MAX_IRQS{1'b1}} << NUM_IRQS);
localparam [3:0] IRQ_PRIORITY_MASK = ~(4'hf >> IRQ_PRIORITY_BITS);
// Assigned later:
@ -342,32 +340,49 @@ reg [MAX_IRQS-1:0] meiea;
reg [MAX_IRQS-1:0] meifa;
reg [4*MAX_IRQS-1:0] meipra;
always @ (posedge clk or negedge rst_n) begin
always @ (posedge clk or negedge rst_n) begin: update_irq_reg_arrays
integer i;
if (!rst_n) begin
meiea <= {MAX_IRQS{1'b0}};
meifa <= {MAX_IRQS{1'b0}};
meipra <= {4*MAX_IRQS{1'b0}};
end else begin
// Tie off unimplemented fields with a constant mask, then rely on
// further constant folding. Otherwise subsequent RTL will get a bit
// out of hand.
// Assign as though all 512 IRQs existed.
if (wen_m_mode && addr == MEIEA) begin
meiea[16 * wdata[4:0] +: 16] <= IRQ_IMPL_MASK[16 * wdata[4:0] +: 16] & wdata_update[31:16];
meiea[16 * wdata[4:0] +: 16] <= wdata_update[31:16];
end else if (wen_m_mode && addr == MEIFA) begin
meifa[16 * wdata[4:0] +: 16] <= IRQ_IMPL_MASK[16 * wdata[4:0] +: 16] & wdata_update[31:16];
meifa[16 * wdata[4:0] +: 16] <= wdata_update[31:16];
end else if (wen_m_mode && addr == MEIPRA) begin
meipra[16 * wdata[6:0] +: 16] <= {
{4{IRQ_IMPL_MASK[4 * wdata[6:0] + 3]}},
{4{IRQ_IMPL_MASK[4 * wdata[6:0] + 2]}},
{4{IRQ_IMPL_MASK[4 * wdata[6:0] + 1]}},
{4{IRQ_IMPL_MASK[4 * wdata[6:0] + 0]}}
} & {4{IRQ_PRIORITY_MASK}} & wdata_update[31:16];
meipra[16 * wdata[6:0] +: 16] <= wdata_update[31:16];
end
// Clear IRQ force when the corresponding IRQ is sample from meinext
// (so that an IRQ can be posted *once* without modifying the ISR source)
if (ren_m_mode && addr == MEINEXT && !meinext_noirq) begin
meifa[meinext_irq] <= 1'b0;
end
// Finally, force all nonimplemented register fields to 0 so they are
// trimmed. Some tools have trouble propagating constants through the
// indexed assignments used above -- a final assignment makes the
// propagation simpler as this is the head of the decision tree.
for (i = 0; i < MAX_IRQS; i = i + 1) begin
if (i >= NUM_IRQS) begin
meiea[i] <= 1'b0;
meifa[i] <= 1'b0;
meipra[4 * i +: 4] <= 4'h0;
end
if (IRQ_PRIORITY_BITS < 4) begin
meipra[4 * i + 0] <= 1'b0;
end
if (IRQ_PRIORITY_BITS < 3) begin
meipra[4 * i + 1] <= 1'b0;
end
if (IRQ_PRIORITY_BITS < 2) begin
meipra[4 * i + 2] <= 1'b0;
end
if (IRQ_PRIORITY_BITS < 1) begin
meipra[4 * i + 3] <= 1'b0;
end
end
end
end