fpga: lib: add extended spi core for 64bit

The existing SPI core (simple_spi_slave.v) was limited to 32 bit. This
commit adds a second spi core with capability to transfer up to 64 bits
while keeping the same amount of resources when using generic setting
MAX_BITS = 32. Furthermore, the new module aligns mosi and miso with the
edges of sclk. The register stages were not aligned in the existing
version.

2 files changed, 287 insertions, 0 deletions

diff --git a/fpga/usrp3/lib/control/Makefile.srcs b/fpga/usrp3/lib/control/Makefile.srcs
index 578f19ea5..21f986a50 100644
--- a/fpga/usrp3/lib/control/Makefile.srcs
+++ b/fpga/usrp3/lib/control/Makefile.srcs
@@ -39,6 +39,7 @@ settings_bus_mux.v \
 settings_bus_timed_2clk.v \
 simple_i2c_core.v \
 simple_spi_core.v \
+simple_spi_core_64bit.v \
 synchronizer_impl.v \
 synchronizer.v \
 pulse_synchronizer.v \
diff --git a/fpga/usrp3/lib/control/simple_spi_core_64bit.v b/fpga/usrp3/lib/control/simple_spi_core_64bit.v
new file mode 100644
index 000000000..fdacd8ea1
--- /dev/null
+++ b/fpga/usrp3/lib/control/simple_spi_core_64bit.v
@@ -0,0 +1,286 @@
+//
+// Copyright 2020 Ettus Research, A National Instruments Company
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+// Module: simple_spi_core_64bit
+// Description:
+// Simple SPI core based on simple_spi_core.v. Extended to 64 bit transmissions
+// while preserving the same control interface for 32 bit transmissions.
+
+// Settings register controlled.
+// 4 settings regs, control and data
+// 1 up to 64-bit readback and status signal
+
+// Settings reg map:
+//
+// BASE+0 divider setting
+// bits [15:0] spi clock divider
+//
+// BASE+1 configuration input
+// bits [23:0] slave select, bit0 = slave0 enabled
+// bits [29:24] num bits (0 through 63; value of 0 transmits 64 bits)
+// bit [30] data input edge = in data bit latched on rising edge of clock
+// bit [31] data output edge = out data bit latched on rising edge of clock
+//
+// BASE+2 input data (bits 63...32)
+// Writing this register begins a spi transaction. If up to 32 bits (MAX_BITS <=
+// 32) are required only this input data register needs to be written. Bits are
+// latched out from bit 63. Therefore, load this register aligning with MSBs.
+//
+// BASE+3 input data (bits 31...0, present if MAX_BITS>32)
+// This register needs to be written before accessing BASE+2 input data
+// register when MAX_BITS > 32.
+//
+// Readback
+// Bits are latched into bit 0.
+
+module simple_spi_core_64bit
+  #(
+    //settings register base address
+    parameter BASE = 0,
+
+    //width of serial enables (up to 24 is possible)
+    parameter WIDTH = 8,
+
+    //idle state of the spi clock
+    parameter CLK_IDLE = 0,
+
+    //idle state of the serial enables
+    parameter SEN_IDLE = 24'hffffff,
+
+    //maximum number of bits for single transmission (<=64)
+    parameter MAX_BITS = 32
+  )
+  (
+    //clock and synchronous reset
+    input clock, input reset,
+
+    //32-bit settings bus inputs
+    input set_stb, input [7:0] set_addr, input [31:0] set_data,
+
+    //up to 64-bit data readback
+    output [MAX_BITS-1:0] readback,
+    output reg readback_stb,
+
+    //read is high when spi core can begin another transaction
+    output ready,
+
+    //spi interface, slave selects, clock, data in, data out
+    output [WIDTH-1:0] sen,
+    output reg sclk,
+    output reg mosi,
+    input miso,
+
+    //optional debug output
+    output [23:0] debug
+  );
+
+  // assert for MAX_BITS
+  generate
+  if (MAX_BITS > 64 || MAX_BITS < 1) begin
+    MAX_BITS_must_be_between_1_and_64();
+  end
+  endgenerate
+
+  wire [15:0] sclk_divider;
+  setting_reg #(.my_addr(BASE+0),.width(16)) divider_sr(
+    .clk(clock),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data),
+    .out(sclk_divider),.changed());
+
+  wire [23:0] slave_select;
+  wire [5:0] num_bits;
+  wire datain_edge, dataout_edge;
+  setting_reg #(.my_addr(BASE+1),.width(32)) ctrl_sr(
+    .clk(clock),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data),
+    .out({dataout_edge, datain_edge, num_bits, slave_select}),.changed());
+
+  wire [63:0] mosi_data;
+  wire trigger_spi;
+  setting_reg #(.my_addr(BASE+2),.width(32)) data_upper_sr(
+    .clk(clock),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data),
+    .out(mosi_data[63:32]),.changed(trigger_spi));
+  setting_reg #(.my_addr(BASE+3),.width(32)) data_lower_sr(
+    .clk(clock),.rst(reset),.strobe(set_stb),.addr(set_addr),.in(set_data),
+    .out(mosi_data[31:0]),.changed());
+
+  localparam WAIT_TRIG = 0;
+  localparam PRE_IDLE = 1;
+  localparam CLK_REG = 2;
+  localparam CLK_INV = 3;
+  localparam POST_IDLE = 4;
+  localparam IDLE_SEN = 5;
+
+  reg [2:0] state;
+
+  reg ready_reg;
+  assign ready = ready_reg && ~trigger_spi;
+
+  //serial clock either idles or is in one of two clock states
+  //One pipeline stage to align output data with clock edge.
+  reg sclk_reg;
+  always @(posedge clock) begin
+    sclk <= sclk_reg;
+  end
+
+  //serial enables either idle or enabled based on state
+  // IJB. One pipeline stage to break critical path from register in I/O pads.
+  wire sen_is_idle = (state == WAIT_TRIG) || (state == IDLE_SEN);
+  wire [23:0] sen24 = (sen_is_idle) ? SEN_IDLE : (SEN_IDLE ^ slave_select);
+  reg [WIDTH-1:0] sen_reg = SEN_IDLE[WIDTH-1:0];
+  always @(posedge clock) begin
+    if (reset) begin
+      sen_reg <= SEN_IDLE[WIDTH-1:0];
+    end else begin
+      sen_reg <= sen24[WIDTH-1:0];
+    end
+  end
+  assign sen = sen_reg;
+
+  //data output shift register
+  // IJB. One pipeline stage to break critical path from register in I/O pads.
+  reg [MAX_BITS-1:0] dataout_reg = {MAX_BITS {1'b0}};
+  wire [MAX_BITS-1:0] dataout_next = {dataout_reg[MAX_BITS-2:0], 1'b0};
+
+  always @(posedge clock) begin
+    mosi <= dataout_reg[MAX_BITS-1];
+  end
+
+  //data input shift register
+  // IJB. Two pipeline stages to break critical path from register in I/O pads.
+  reg  miso_pipe, miso_pipe2;
+  always @(posedge clock) begin
+    miso_pipe2 <= miso;
+    miso_pipe <= miso_pipe2;
+  end
+
+  // Register to control input data capturing, compensating 2 miso_pipe
+  // registers and the output register on mosi/sclk.
+  //
+  // When sclk_counter_done is asserted the FSM below updates sclk_reg and
+  // dataout_reg (compensated by datain_capture_reg).
+  // One clock cycle later those values get propagated to sclk and mosi. On
+  // the active datain_edge miso would be capture into miso_pipe2. This clock
+  // cycle is compensated by datain_capture_pipe[0].
+  // Propagation of miso data to miso_pipe is compensated by
+  // datain_capture_pipe[1].
+  // On the next clock edge datain_capture_pipe[1] serves as enable signal for
+  // datain_reg which then consumes the aligned data from miso_pipe.
+  reg datain_capture_reg = 1'b0;
+  reg [1:0] datain_capture_pipe;
+  wire capturing_done = ~| {datain_capture_reg, datain_capture_pipe};
+
+  reg [MAX_BITS-1:0] datain_reg;
+  wire [MAX_BITS-1:0] datain_next = {datain_reg[MAX_BITS-2:0], miso_pipe};
+  assign readback = datain_reg;
+
+  always @(posedge clock) begin
+    datain_capture_pipe <= {datain_capture_pipe[0], datain_capture_reg};
+    if (datain_capture_pipe[1]) begin
+      datain_reg <= datain_next;
+    end
+  end
+
+  //counter for spi clock
+  reg [15:0] sclk_counter = 16'b0;
+  wire sclk_counter_done = (sclk_counter == sclk_divider);
+  wire [15:0] sclk_counter_next = (sclk_counter_done)? 0 : sclk_counter + 1;
+
+  //counter for latching bits miso/mosi
+  reg [5:0] bit_counter = 6'b0;
+  wire [5:0] bit_counter_next = bit_counter + 1;
+  wire bit_counter_done = (bit_counter_next == num_bits);
+
+  always @(posedge clock) begin
+    if (reset) begin
+      state <= WAIT_TRIG;
+      sclk_reg <= CLK_IDLE;
+      ready_reg <= 0;
+      readback_stb <= 1'b0;
+    end else begin
+      datain_capture_reg <= 1'b0;
+
+      case (state)
+        WAIT_TRIG: begin
+          if (trigger_spi) begin
+            state <= PRE_IDLE;
+          end
+          readback_stb <= 1'b0;
+          ready_reg <= ~trigger_spi;
+          dataout_reg <= mosi_data[63:64-MAX_BITS];
+          sclk_counter <= 0;
+          bit_counter <= 0;
+          sclk_reg <= CLK_IDLE;
+        end
+
+        PRE_IDLE: begin
+          if (sclk_counter_done) begin
+            state <= CLK_REG;
+          end
+          sclk_counter <= sclk_counter_next;
+          sclk_reg <= CLK_IDLE;
+        end
+
+        CLK_REG: begin
+          if (sclk_counter_done) begin
+            state <= CLK_INV;
+            if (datain_edge  != CLK_IDLE) begin
+              datain_capture_reg <= 1'b1;
+            end
+            if (dataout_edge != CLK_IDLE && bit_counter != 0) begin
+              dataout_reg <= dataout_next;
+            end
+            sclk_reg <= ~CLK_IDLE; //transition to rising when CLK_IDLE == 0
+          end
+          sclk_counter <= sclk_counter_next;
+        end
+
+        CLK_INV: begin
+          if (sclk_counter_done) begin
+            state <= (bit_counter_done) ? POST_IDLE : CLK_REG;
+            bit_counter <= bit_counter_next;
+            if (datain_edge  == CLK_IDLE) begin
+              datain_capture_reg <= 1'b1;
+            end
+            if (dataout_edge == CLK_IDLE && ~bit_counter_done) begin
+              dataout_reg <= dataout_next;
+            end
+            sclk_reg <= CLK_IDLE; //transition to falling when CLK_IDLE == 0
+          end
+          sclk_counter <= sclk_counter_next;
+        end
+
+        POST_IDLE: begin
+          if (sclk_counter_done) begin
+            state <= IDLE_SEN;
+          end
+          sclk_counter <= sclk_counter_next;
+          sclk_reg <= CLK_IDLE;
+        end
+
+        IDLE_SEN: begin
+          if (sclk_counter_done && capturing_done) begin
+            ready_reg <= 1'b1;
+            readback_stb <= 1'b1;
+            state <= WAIT_TRIG;
+          end
+          sclk_counter <= sclk_counter_next;
+          sclk_reg <= CLK_IDLE;
+        end
+
+        default: begin
+          state <= WAIT_TRIG;
+        end
+      endcase //state
+    end
+  end
+
+  assign debug = {
+    trigger_spi, state, //4
+    sclk, mosi, miso, ready, //4
+    2'b0, bit_counter[5:0], //8
+    sclk_counter_done, bit_counter_done, //2
+    sclk_counter[5:0] //6
+  };
+
+endmodule //simple_spi_core