padding of 802.1q tagged frames when they are going to be untagged

If we don't pad 802.1q frames 4-bytes more than regular frames, they become runt frames after untagging (when port is in ACCESS mode).

padding of 802.1q tagged frames when they are going to be untagged
If we don't pad 802.1q frames 4-bytes more than regular frames, they become runt frames after untagging (when port is in ACCESS mode).
62324a27 · Grzegorz Daniluk · 8c23ba5d · 62324a27
Commit 62324a27 authored Feb 10, 2015 by Grzegorz Daniluk
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ep_tx_header_processor.vhd modules/wr_endpoint/ep_tx_header_processor.vhd +34 -6

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--- a/modules/wr_endpoint/ep_tx_header_processor.vhd
+++ b/modules/wr_endpoint/ep_tx_header_processor.vhd
@@ -135,6 +135,10 @@ end ep_tx_header_processor;
 architecture behavioral of ep_tx_header_processor is

  constant c_IFG_LENGTH : integer := g_force_gap_length ;--0;
+  constant c_MIN_FRAME_THR  : integer := 30;
+  constant c_MIN_QFRAME_THR : integer := 32; -- we need to pad more 802.1q
+                                             -- tagged frame if it's going to be
+                                             -- untagged later in the tx_path

  type t_tx_framer_state is (TXF_IDLE, TXF_DELAYED_SOF, TXF_ADDR, TXF_DATA, TXF_GAP, TXF_PAD, TXF_ABORT, TXF_STORE_TSTAMP);

@@ -166,7 +170,8 @@ architecture behavioral of ep_tx_header_processor is
  signal tx_en        : std_logic;
  signal ep_ctrl     : std_logic;
  signal bitsel_d    : std_logic;
-  signal needs_padding  :  std_logic;
+  signal needs_padding  : std_logic;
+  signal to_be_untagged : std_logic;
  signal sof_reg     : std_logic;

  function b2s (x : boolean)
@@ -198,7 +203,16 @@ architecture behavioral of ep_tx_header_processor is
      return when_0;
    end if;
  end function;
-  
+
+  function f_pick (cond : boolean; when_1 : std_logic ; when_0 : std_logic)
+    return std_logic is
+  begin
+    if(cond) then
+      return when_1;
+    else
+      return when_0;
+    end if;
+  end function;
  
  function f_fabric_2_slv (
    in_i : t_wrf_sink_in;
@@ -246,11 +260,15 @@ begin  -- behavioral
              '0'; -- ML

  GEN_PADDING: if(g_runt_padding) generate
-    needs_padding <= '1' when(counter < x"1e") else -- 0x1e, but we count here also ethertype
+    needs_padding <= '1' when( (to_be_untagged = '1' and counter < c_MIN_QFRAME_THR) or
+                                counter < c_MIN_FRAME_THR) else
                     '0';
  end generate;
  GEN_NOPADDING: if( not g_runt_padding) generate
-    needs_padding <= '0';
+    -- even if padding is disabled, we still need to pad short 802.1q frames
+    -- that will be untagged
+    needs_padding <= '1' when (to_be_untagged = '1' and counter < c_MIN_QFRAME_THR) else
+                     '0';
  end generate;

  process(clk_sys_i)
@@ -341,7 +359,8 @@ begin  -- behavioral
        fc_pause_ready_o <= '1';

        txtsu_stb_o <= '0';
-        bitsel_d  <='0';
+        bitsel_d  <= '0';
+        to_be_untagged <= '0';

      else

@@ -384,6 +403,7 @@ begin  -- behavioral
              src_fab_o.eof    <= '0';
              src_fab_o.dvalid <= '0';
              src_fab_o.bytesel <= '0';
+              to_be_untagged    <= '0';

              -- Check start-of-frame and send-pause signals and eventually
              -- commence frame transmission
@@ -452,6 +472,8 @@ begin  -- behavioral
                    end if;
                  when x"6" =>
                    src_fab_o.data <= f_pick(g_with_packet_injection, "XXXXXXXXXXXXXXXX", x"8808");
+                    to_be_untagged <= f_pick(wb_snk_i.dat = x"8100" and
+                                             regs_i.vcr0_qmode_o = c_QMODE_PORT_ACCESS, '1', '0');
                  when x"7" =>
                    src_fab_o.data <= f_pick(g_with_packet_injection, "XXXXXXXXXXXXXXXX", x"0001"); -- peterj: IEEE 802.3 Table 31A-1 MAC control codes PAUSE (Annex 31B)
                  when x"8" =>
@@ -482,7 +504,8 @@ begin  -- behavioral
                src_fab_o.dvalid <= '1';
                src_fab_o.addr   <= (others => '0');

-                if(counter = x"1d") then
+                if( (to_be_untagged = '1' and counter = c_MIN_QFRAME_THR-1) or
+                    (to_be_untagged = '0' and counter = c_MIN_FRAME_THR-1) ) then
                  state <= TXF_GAP;
                  src_fab_o.eof    <= '1';
                end if;
@@ -504,6 +527,11 @@ begin  -- behavioral
              -- src_fab_o.eof to HIGH but actually did not exit the TXF_DATA state... this
              -- caused EOF to be longer than one cycle
              src_fab_o.eof   <= '0'; 
+
+              if (counter = x"6") then
+                to_be_untagged <= f_pick(wb_snk_i.dat = x"8100" and
+                                         regs_i.vcr0_qmode_o = c_QMODE_PORT_ACCESS, '1', '0');
+              end if;
              
              if((wb_snk_i.adr = c_WRF_OOB or eof_p1='1') and needs_padding='1') then
                state <= TXF_PAD;