As the title says, I’ve enabled the FPGA2SDRAM interface in my HPS and have written an Avalon Memory Mapped Host/Master to write to a specific memory location.
It’s a very simple code, based off the template in platform designer and it works fine:
`timescale 1 ps / 1 ps
module mem_write (
output logic [31:0] avm_m0_address, // avm_m0.address
input logic avm_m0_waitrequest, // .waitrequest
output logic avm_m0_write, // .write
output logic [31:0] avm_m0_writedata, // .writedata
input logic clk, // clock.clk
input logic reset, // reset.reset
input logic [31:0] in_address
);
reg [31:0] cnt;
assign avm_m0_address = in_address;
assign avm_m0_write = 1'b1;
assign avm_m0_writedata = {30'd0, cnt[26], cnt[25]};
always_ff @(posedge clk) begin
cnt <= cnt + 1'b1;
end
endmodule
I hardcoded in_address in my top level design to be 32'h20000000 (512MB).
This works fine and I can see it cycling through 0-3 at 0x20000000 at regular intervals with the command:
busybox devmem 0x20000000
But when I try to do the reverse, i.e. read from the same memory location, linux hangs.
Here is my code:
`timescale 1 ps / 1 ps
module mem_read (
output logic [31:0] avm_m0_address, // avm_m0.address
output logic avm_m0_read, // .read
input logic avm_m0_waitrequest, // .waitrequest
input logic [31:0] avm_m0_readdata, // .readdata
input logic clk, // clock.clk
input logic reset, // reset.reset
input logic [31:0] in_address,
output logic [31:0] out_data
);
reg [31:0] readdata;
assign avm_m0_address = in_address;
assign out_data = readdata;
assign avm_m0_read = 1'b1;
always_ff @(posedge clk) begin
if (reset) begin
readdata <= 32'd0;
end else begin
if (avm_m0_waitrequest) begin
readdata <= readdata;
end else begin
readdata <= avm_m0_readdata;
end
end
end
endmodule
Is there something wrong with my code?
I’ve set up the FPGA2SDRAM in HPS to be bi-directional and 256 bits.
Here is a screenshot of platform designer:
. I spent a few days struggling to understand this, but since I have no idea how to use Modelsim also, I just abandoned this. If you have any links or references for beginners on how to use BFM, I’d appreciate it!