wr_mini_nic: cleanup for overflow management

when there is not enough space in the buffer, the incoming frame is going to be ignored. Some unnecessary "buffer full" checks has been removed. Patch disclaimer: this patch doesn't claim to fix all the possible overflow situations in the circular buffer of the mini-nic.

wr_mini_nic: cleanup for overflow management
when there is not enough space in the buffer, the incoming frame is going to be ignored. Some unnecessary "buffer full" checks has been removed. Patch disclaimer: this patch doesn't claim to fix all the possible overflow situations in the circular buffer of the mini-nic.
fc45a261 · Cesar Prados · 46b14b94 · fc45a261
Commit fc45a261 authored Jun 10, 2016 by Cesar Prados
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Showing with 16 additions and 28 deletions

wr_mini_nic.vhd modules/wr_mini_nic/wr_mini_nic.vhd +16 -28

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--- a/modules/wr_mini_nic/wr_mini_nic.vhd
+++ b/modules/wr_mini_nic/wr_mini_nic.vhd
@@ -764,13 +764,15 @@ begin  -- behavioral
                if(nrx_avail /= to_unsigned(0, nrx_avail'length)) then
                  nrx_avail  <= nrx_avail - 1;
                  nrx_mem_wr <= '1';
+                  nrx_state <= RX_DATA;
+                else
+                  nrx_state <= RX_IGNORE;
+                  nrx_buf_full <= '1';
                end if;

-
                -- allow the fabric to receive the data
                nrx_stall_mask <= '0';

-                nrx_state <= RX_DATA;
              end if;

 -------------------------------------------------------------------------------
@@ -786,21 +788,18 @@ begin  -- behavioral
              end if;

              -- check if we have enough space in the buffer
-              if(nrx_avail = to_unsigned(0, nrx_avail'length)) then
+              if(nrx_avail = to_unsigned(4, nrx_avail'length)) then
                nrx_buf_full <= '1';
-              end if;
-
-              -- we've got a valid data word or end-of-frame/error condition
-              if(nrx_valid = '1' or nrx_stat_error = '1' or snk_cyc_i = '0') then
-
+                nrx_state <= RX_IGNORE;
+              elsif(nrx_valid = '1' or nrx_stat_error = '1' or snk_cyc_i = '0') then
+                -- we've got a valid data word or end-of-frame/error condition
                -- latch the bytesel signal to support frames having odd lengths
                if(snk_sel_i = "10") then
                  nrx_bytesel <= '1';
                end if;

                -- abort/error/end-of-frame?
-                if(nrx_stat_error = '1' or snk_cyc_i = '0' or nrx_avail = to_unsigned(0, nrx_avail'length)) then
-
+                if(nrx_stat_error = '1' or snk_cyc_i = '0') then
                  if(nrx_stat_error = '1' or nrx_avail = to_unsigned(0, nrx_avail'length)) then
                    nrx_error <= '1';
                  else
@@ -914,19 +913,13 @@ begin  -- behavioral
 -------------------------------------------------------------------------------

            when RX_MEM_FLUSH =>
+            
+              -- there is space in the buffer for sure
              nrx_stall_mask <= '1';
-
-              if(nrx_buf_full = '0') then
-                nrx_mem_wr <= '1';
-              end if;
-
+              nrx_mem_wr <= '1';
+ 
              if(mem_arb_rx = '0') then
-                if(nrx_buf_full = '0') then
-                  nrx_avail <= nrx_avail - 1;
-                else
-                	nrx_size <= nrx_size - 1;  --the buffer is full, last word was not written
-                	nrx_mem_a <= nrx_mem_a - 1;
-                end if;
+                nrx_avail <= nrx_avail - 1;
                nrx_state <= RX_UPDATE_DESC;
              end if;

@@ -940,10 +933,6 @@ begin  -- behavioral
            when RX_UPDATE_DESC =>
              nrx_stall_mask <= '1';

-              if(nrx_avail = to_unsigned(0, nrx_avail'length)) then
-                nrx_buf_full <= '1';
-              end if;
-
              if(mem_arb_rx = '0') then


@@ -974,9 +963,6 @@ begin  -- behavioral
                -- wait for another packet
                if(snk_cyc_i = '1') then
                  nrx_state <= RX_IGNORE;
-                elsif(nrx_buf_full = '1') then
-                  nrx_state      <= RX_BUF_FULL;
-                  nrx_stall_mask <= '1';
                else
                  -- trigger the RX interrupt and assert RX_READY flag to inform
                  -- the host that we've received something
@@ -992,6 +978,8 @@ begin  -- behavioral
              nrx_mem_wr <= '0';
              --drop the rest of the packet
              nrx_stall_mask <= '0';
+              -- reuse this DMA address
+              nrx_mem_a <= nrx_mem_a_saved;
              if(snk_cyc_i = '0') then
                if(nrx_buf_full = '1') then
                  nrx_stall_mask <= '1';