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`include "gfx/gfx_defs.sv"
module gfx_scanout
(
input logic clk,
rst_n,
input logic enable_clear,
input rgb24 clear_color,
input logic mask,
output linear_coord mask_addr,
input logic fb_waitrequest,
fb_readdatavalid,
input vram_word fb_readdata,
output logic fb_read,
output half_coord fb_address,
input logic scan_ready,
output logic scan_valid,
scan_endofpacket,
scan_startofpacket,
output rgb30 scan_data,
output logic vsync
);
logic commit, effective_mask, flush, mask_fifo_out, dac_ready,
fb_ready, mask_fifo_ready, fb_fifo_valid, mask_fifo_valid,
pop, put, put_mask, next_vsync, start_vsync, wait_vsync;
vram_word fb_fifo_out;
half_coord commit_addr, mask_in_addr, mask_out_addr, mask_hold_addr, max_addr;
assign mask_addr = mask_in_addr[$bits(mask_in_addr) - 1:$bits(mask_in_addr) - $bits(mask_addr)];
assign max_addr[0] = 1;
assign max_addr[$bits(max_addr) - 1:1] = `GFX_X_RES * `GFX_Y_RES - 1;
assign fb_ready = !fb_read || !fb_waitrequest;
assign next_vsync = commit && start_vsync;
assign start_vsync = mask_hold_addr == max_addr;
assign effective_mask = mask || !enable_clear;
gfx_flush_flow #(.STAGES(`GFX_MASK_STAGES)) mask_flow
(
.in_valid(!wait_vsync),
.out_ready(fb_ready && mask_fifo_ready && !next_vsync),
.out_valid(pop),
.*
);
gfx_pipes #(.WIDTH($bits(mask_in_addr)), .DEPTH(`GFX_MASK_STAGES)) addr_pipes
(
.in(mask_in_addr),
.out(mask_out_addr),
.stall(0),
.*
);
/* Estas FIFOs deben cumplir dos propiedades para garantizar correctitud:
*
* 1. mask_fifo.out_ready && mask_fifo.out_valid <=> scan.in_ready && scan.in_valid
* 2. fb_fifo.out_ready && fb_fifo.out_valid => scan.in_ready && scan.in_valid
*
* Nótese la asimetría (<=> vs =>), debido a mask_fifo.out
*/
gfx_fifo #(.WIDTH($bits(effective_mask)), .DEPTH(`GFX_SCANOUT_FIFO_DEPTH)) mask_fifo
(
.in(put_mask),
.out(mask_fifo_out),
.in_ready(mask_fifo_ready),
.in_valid(put),
.out_ready(dac_ready && (!mask_fifo_out || fb_fifo_valid)),
.out_valid(mask_fifo_valid),
.*
);
// 2x para evitar potencial overflow cuando fb_read=1 pero mask_fifo está llena
gfx_fifo #(.WIDTH($bits(vram_word)), .DEPTH(2 * `GFX_SCANOUT_FIFO_DEPTH)) fb_fifo
(
.in(fb_readdata),
.out(fb_fifo_out),
.in_ready(), // readdatavalid no soporta backpressure
.in_valid(fb_readdatavalid),
.out_ready(dac_ready && mask_fifo_valid && mask_fifo_out),
.out_valid(fb_fifo_valid),
.*
);
gfx_scanout_dac dac
(
.in_ready(dac_ready),
.in_valid(mask_fifo_valid && (!mask_fifo_out || fb_fifo_valid)),
.*
);
always_ff @(posedge clk or negedge rst_n)
if (!rst_n) begin
put <= 0;
fb_read <= 0;
wait_vsync <= 0;
commit_addr <= 0;
mask_in_addr <= 0;
end else begin
mask_in_addr <= mask_in_addr + 1;
if (flush || wait_vsync)
mask_in_addr <= commit_addr;
if (commit) begin
wait_vsync <= start_vsync;
commit_addr <= start_vsync ? 0 : mask_out_addr;
end
if (fb_ready)
fb_read <= mask_fifo_ready && pop && !next_vsync && effective_mask;
if (mask_fifo_ready)
put <= fb_ready && pop && !next_vsync;
if (vsync)
wait_vsync <= 0;
end
always_ff @(posedge clk) begin
mask_hold_addr <= mask_out_addr;
if (fb_ready)
fb_address <= mask_out_addr;
if (mask_fifo_ready)
put_mask <= effective_mask;
end
endmodule
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