pluto_hdl_adi/library/axi_dmac/axi_dmac_reset_manager.v

305 lines
8.7 KiB
Verilog

// ***************************************************************************
// ***************************************************************************
// Copyright 2014 - 2018 (c) Analog Devices, Inc. All rights reserved.
//
// In this HDL repository, there are many different and unique modules, consisting
// of various HDL (Verilog or VHDL) components. The individual modules are
// developed independently, and may be accompanied by separate and unique license
// terms.
//
// The user should read each of these license terms, and understand the
// freedoms and responsibilities that he or she has by using this source/core.
//
// This core is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE.
//
// Redistribution and use of source or resulting binaries, with or without modification
// of this file, are permitted under one of the following two license terms:
//
// 1. The GNU General Public License version 2 as published by the
// Free Software Foundation, which can be found in the top level directory
// of this repository (LICENSE_GPL2), and also online at:
// <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
//
// OR
//
// 2. An ADI specific BSD license, which can be found in the top level directory
// of this repository (LICENSE_ADIBSD), and also on-line at:
// https://github.com/analogdevicesinc/hdl/blob/master/LICENSE_ADIBSD
// This will allow to generate bit files and not release the source code,
// as long as it attaches to an ADI device.
//
// ***************************************************************************
// ***************************************************************************
`timescale 1ns/100ps
module axi_dmac_reset_manager #(
parameter ASYNC_CLK_REQ_SRC = 1,
parameter ASYNC_CLK_SRC_DEST = 1,
parameter ASYNC_CLK_DEST_REQ = 1
) (
input clk,
input resetn,
input ctrl_enable,
input ctrl_pause,
output req_resetn,
output req_enable,
input req_enabled,
input dest_clk,
input dest_ext_resetn,
output dest_resetn,
output dest_enable,
input dest_enabled,
input src_clk,
input src_ext_resetn,
output src_resetn,
output src_enable,
input src_enabled,
output [11:0] dbg_status
);
/*
* TODO:
* If an external reset is asserted for a domain that domain will go into reset
* immediately. If a transfer is currently active the transfer will be aborted
* and other domains will be shutdown gracefully. The reset manager will stay in
* the shutdown state until all external resets have been de-asserted.
*/
localparam STATE_DO_RESET = 3'h0;
localparam STATE_RESET = 3'h1;
localparam STATE_DISABLED = 3'h2;
localparam STATE_STARTUP = 3'h3;
localparam STATE_ENABLED = 3'h4;
localparam STATE_SHUTDOWN = 3'h5;
reg [2:0] state = 3'b000;
reg needs_reset = 1'b0;
reg do_reset = 1'b0;
reg do_enable = 1'b0;
wire enabled_dest;
wire enabled_src;
wire enabled_all;
wire disabled_all;
assign enabled_all = req_enabled & enabled_src & enabled_dest;
assign disabled_all = ~(req_enabled | enabled_src | enabled_dest);
assign req_enable = do_enable;
assign dbg_status = {needs_reset,req_resetn,src_resetn,dest_resetn,1'b0,req_enabled,enabled_src,enabled_dest,1'b0,state};
always @(posedge clk) begin
if (state == STATE_DO_RESET) begin
do_reset <= 1'b1;
end else begin
do_reset <= 1'b0;
end
end
always @(posedge clk) begin
if (state == STATE_STARTUP || state == STATE_ENABLED) begin
do_enable <= 1'b1;
end else begin
do_enable <= 1'b0;
end
end
/*
* If ctrl_enable goes from 1 to 0 a shutdown procedure is initiated. During the
* shutdown procedure all domains are signaled that a shutdown should occur. The
* domains will then complete any active transactions that are required to
* complete according to the interface semantics. Once a domain has completed
* its transactions it will indicate that it has been shutdown. Once all domains
* indicate that they have been disabled a reset pulse will be generated to all
* domains to clear all residual state. The reset pulse is long enough so that it
* is active in all domains for at least 4 clock cycles.
*
* Once the reset signal is de-asserted the DMA is in an idle state and can be
* enabled again. If the DMA receives a enable while it is performing a shutdown
* sequence it will only be re-enabled once the shutdown sequence has
* successfully completed.
*
* If ctrl_pause is asserted all domains will be disabled. But there will be no
* reset, so when the ctrl_pause signal is de-asserted again the DMA will resume
* with its previous state.
*
*/
/*
* If ctrl_enable goes low, even for a single clock cycle, we want to go through
* a full reset sequence. This might happen when the state machine is busy, e.g.
* going through a startup sequence. To avoid missing the event store it for
* later.
*/
always @(posedge clk) begin
if (state == STATE_RESET) begin
needs_reset <= 1'b0;
end else if (ctrl_enable == 1'b0) begin
needs_reset <= 1'b1;
end
end
always @(posedge clk) begin
if (resetn == 1'b0) begin
state <= STATE_DO_RESET;
end else begin
case (state)
STATE_DO_RESET: begin
state <= STATE_RESET;
end
STATE_RESET: begin
/*
* Wait for the reset sequence to complete. Stay in this state when
* ctrl_enable == 1'b0, otherwise we'd go through the reset sequence
* again and again.
*/
if (ctrl_enable == 1'b1 && req_resetn == 1'b1) begin
state <= STATE_DISABLED;
end
end
STATE_DISABLED: begin
if (needs_reset == 1'b1) begin
state <= STATE_DO_RESET;
end else if (ctrl_pause == 1'b0) begin
state <= STATE_STARTUP;
end
end
STATE_STARTUP: begin
/* Wait for all domains to be ready */
if (enabled_all == 1'b1) begin
state <= STATE_ENABLED;
end
end
STATE_ENABLED: begin
if (needs_reset == 1'b1 || ctrl_pause == 1'b1) begin
state <= STATE_SHUTDOWN;
end
end
STATE_SHUTDOWN: begin
/* Wait for all domains to complete outstanding transactions */
if (disabled_all == 1'b1) begin
state <= STATE_DISABLED;
end
end
endcase
end
end
/*
* Chain the reset through all clock domains. This makes sure that is asserted
* for at least 4 clock cycles of the slowest domain, no matter what. If
* successive domains have the same clock they'll share their reset signal.
*/
wire [3:0] reset_async_chain;
wire [3:0] reset_sync_chain;
wire [2:0] reset_chain_clks = {clk, src_clk, dest_clk};
localparam GEN_ASYNC_RESET = {
ASYNC_CLK_REQ_SRC ? 1'b1 : 1'b0,
ASYNC_CLK_SRC_DEST ? 1'b1 : 1'b0,
1'b1
};
assign reset_async_chain[0] = 1'b0;
assign reset_sync_chain[0] = reset_async_chain[3];
generate
genvar i;
for (i = 0; i < 3; i = i + 1) begin: reset_gen
if (GEN_ASYNC_RESET[i] == 1'b1) begin
reg [3:0] reset_async = 4'b1111;
reg [1:0] reset_sync = 2'b11;
reg reset_sync_in = 1'b1;
always @(posedge reset_chain_clks[i] or posedge reset_sync_chain[i]) begin
if (reset_sync_chain[i] == 1'b1) begin
reset_sync_in <= 1'b1;
end else begin
reset_sync_in <= reset_async[0];
end
end
always @(posedge reset_chain_clks[i] or posedge do_reset) begin
if (do_reset == 1'b1) begin
reset_async <= 4'b1111;
end else begin
reset_async <= {reset_async_chain[i], reset_async[3:1]};
end
end
always @(posedge reset_chain_clks[i]) begin
reset_sync <= {reset_sync_in,reset_sync[1]};
end
assign reset_async_chain[i+1] = reset_async[0];
assign reset_sync_chain[i+1] = reset_sync[0];
end else begin
assign reset_async_chain[i+1] = reset_async_chain[i];
assign reset_sync_chain[i+1] = reset_sync_chain[i];
end
end
endgenerate
/* De-assertions in the opposite direction of the data flow: dest, src, request */
assign dest_resetn = ~reset_sync_chain[1];
assign src_resetn = ~reset_sync_chain[2];
assign req_resetn = ~reset_sync_chain[3];
sync_bits #(
.NUM_OF_BITS (1),
.ASYNC_CLK (ASYNC_CLK_DEST_REQ)
) i_sync_control_dest (
.out_clk (dest_clk),
.out_resetn (1'b1),
.in_bits (do_enable),
.out_bits (dest_enable)
);
sync_bits #(
.NUM_OF_BITS (1),
.ASYNC_CLK (ASYNC_CLK_DEST_REQ)
) i_sync_status_dest (
.out_clk (clk),
.out_resetn (1'b1),
.in_bits (dest_enabled),
.out_bits (enabled_dest)
);
sync_bits #(
.NUM_OF_BITS (1),
.ASYNC_CLK (ASYNC_CLK_REQ_SRC)
) i_sync_control_src (
.out_clk (src_clk),
.out_resetn (1'b1),
.in_bits (do_enable),
.out_bits (src_enable)
);
sync_bits #(
.NUM_OF_BITS (1),
.ASYNC_CLK (ASYNC_CLK_REQ_SRC)
) i_sync_status_src (
.out_clk (clk),
.out_resetn (1'b1),
.in_bits (src_enabled),
.out_bits (enabled_src)
);
endmodule