SPI Engine: fix segmented transfers with echo_sclk

Signed-off-by: Laez Barbosa <[email protected]>
analogdevicesinc · Nov 28, 2024 · d10c959 · d10c959
1 parent 741e53f
commit d10c959
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Showing 2 changed files with 11 additions and 41 deletions.
diff --git a/library/spi_engine/spi_engine_execution/spi_engine_execution.v b/library/spi_engine/spi_engine_execution/spi_engine_execution.v
@@ -163,8 +163,6 @@ module spi_engine_execution #(
   wire io_ready1;
   wire io_ready2;
 
-  wire end_of_sdi_latch;
-
   wire sample_sdo;
 
   (* direct_enable = "yes" *) wire cs_gen;
@@ -200,8 +198,7 @@ module spi_engine_execution #(
     .trigger_tx(trigger_tx),
     .trigger_rx(trigger_rx),
     .first_bit(first_bit),
-    .cs_activate(cs_activate),
-    .end_of_sdi_latch(end_of_sdi_latch));
+    .cs_activate(cs_activate));
 
   assign sample_sdo = sdo_data_valid && ((trigger_tx && last_bit) || (wait_for_io || exec_transfer_cmd));
 
@@ -331,7 +328,7 @@ module spi_engine_execution #(
       end else begin
         case (inst_d1)
         CMD_TRANSFER: begin
-          if (transfer_active == 1'b0 && wait_for_io == 1'b0 && end_of_sdi_latch == 1'b1)
+          if (transfer_active == 1'b0 && wait_for_io == 1'b0)
             idle <= 1'b1;
         end
         CMD_CHIPSELECT: begin

diff --git a/library/spi_engine/spi_engine_execution/spi_engine_execution_shiftreg.v b/library/spi_engine/spi_engine_execution/spi_engine_execution_shiftreg.v
@@ -76,8 +76,7 @@ module spi_engine_execution_shiftreg #(
   input       trigger_tx,
   input       trigger_rx,
   input       first_bit,
-  input       cs_activate,
-  output      end_of_sdi_latch
+  input       cs_activate
 );
 
   reg [             7:0] sdi_counter    = 8'b0;
@@ -156,9 +155,7 @@ module spi_engine_execution_shiftreg #(
   generate
   if (ECHO_SCLK == 1) begin : g_echo_sclk_miso_latch
 
-    reg [7:0] sdi_counter_d = 8'b0;
-    reg [7:0] sdi_transfer_counter = 8'b0;
-    reg [7:0] num_of_transfers = 8'b0;
+    reg last_sdi_bit_r;
     reg [(NUM_OF_SDI * DATA_WIDTH)-1:0] sdi_data_latch = {(NUM_OF_SDI * DATA_WIDTH){1'b0}};
 
     if ((DEFAULT_SPI_CFG[1:0] == 2'b01) || (DEFAULT_SPI_CFG[1:0] == 2'b10)) begin : g_echo_miso_nshift_reg
@@ -185,10 +182,10 @@ module spi_engine_execution_shiftreg #(
       always @(posedge echo_sclk or posedge cs_activate) begin
         if (cs_activate) begin
           sdi_counter <= 8'b0;
-          sdi_counter_d <= 8'b0;
+          last_sdi_bit_r <= 1'b0;
         end else begin
-          sdi_counter <= (sdi_counter == word_length-1) ? 8'b0 : sdi_counter + 1'b1;
-          sdi_counter_d <= sdi_counter;
+          last_sdi_bit_r <= (sdi_counter == word_length - 1); // FIXME: potentially unsafe path: what are the guarantees of settling time between changing word_length and first echo_sclk edge?
+          sdi_counter <= (sdi_counter == word_length - 1) ? 8'b0 : sdi_counter + 1'b1;
         end
       end
 
@@ -214,17 +211,17 @@ module spi_engine_execution_shiftreg #(
       always @(posedge echo_sclk or posedge cs_activate) begin
         if (cs_activate) begin
           sdi_counter <= 8'b0;
-          sdi_counter_d <= 8'b0;
+          last_sdi_bit_r <= 1'b0;
         end else begin
-          sdi_counter <= (sdi_counter == word_length-1) ? 8'b0 : sdi_counter + 1'b1;
-          sdi_counter_d <= sdi_counter;
+          last_sdi_bit_r <= (sdi_counter == word_length - 1); // FIXME: potentially unsafe path: what are the guarantees of settling time between changing word_length and first echo_sclk edge?
+          sdi_counter <= (sdi_counter == word_length - 1) ? 8'b0 : sdi_counter + 1'b1;
         end
       end
 
     end
 
     assign sdi_data = sdi_data_latch;
-    assign last_sdi_bit = (sdi_counter == 0) && (sdi_counter_d == word_length-1);
+    assign last_sdi_bit = last_sdi_bit_r;
 
     // sdi_data_valid is synchronous to SPI clock, so synchronize the
     // last_sdi_bit to SPI clock
@@ -250,34 +247,10 @@ module spi_engine_execution_shiftreg #(
       end
     end
 
-    always @(posedge clk) begin
-      if (cs_activate) begin
-        num_of_transfers <= 8'b0;
-      end else begin
-        if (current_instr == CMD_TRANSFER) begin
-          // current_cmd contains the NUM_OF_TRANSFERS - 1
-          num_of_transfers <= current_cmd[7:0] + 1'b1;
-        end
-      end
-    end
-
-    always @(posedge clk) begin
-      if (cs_activate) begin
-        sdi_transfer_counter <= 0;
-      end else if (last_sdi_bit_m[2] == 1'b0 &&
-                   last_sdi_bit_m[1] == 1'b1) begin
-        sdi_transfer_counter <= sdi_transfer_counter + 1'b1;
-      end
-    end
-
-    assign end_of_sdi_latch = last_sdi_bit_m[2] & (sdi_transfer_counter == num_of_transfers);
-
   end /* g_echo_sclk_miso_latch */
   else
   begin : g_sclk_miso_latch
 
-    assign end_of_sdi_latch = 1'b1;
-
     for (i=0; i<NUM_OF_SDI; i=i+1) begin: g_sdi_shift_reg
 
       reg [DATA_WIDTH-1:0] data_sdi_shift;