modules/swcore: prevent transfer fsm from hanging in DROP when force free was not requested

In the situation when RCV fsm was dropping the whole frame (no pages were used) it was not raising force_free request. However, transfer fsm always waits for force free to be done once it gets to DROP state. This commit adds rp_drop_no_ff signal which is asserted by RCV fsm when it goes to DROP, but does not request force free.

modules/swcore: prevent transfer fsm from hanging in DROP when force free was not requested
In the situation when RCV fsm was dropping the whole frame (no pages were used) it was not raising force_free request. However, transfer fsm always waits for force free to be done once it gets to DROP state. This commit adds rp_drop_no_ff signal which is asserted by RCV fsm when it goes to DROP, but does not request force free.
cfe50f15 · Grzegorz Daniluk · 4618fd1f · cfe50f15
Commit cfe50f15 authored Mar 26, 2015 by Grzegorz Daniluk
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xswc_input_block.vhd modules/wrsw_swcore/xswc_input_block.vhd +11 -0

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--- a/modules/wrsw_swcore/xswc_input_block.vhd
+++ b/modules/wrsw_swcore/xswc_input_block.vhd
@@ -510,6 +510,11 @@ architecture syn of xswc_input_block is
  -- if HIGH, it means that we are receiving/writting the first page of the pck
  signal rp_rcv_first_page : std_logic;

+  signal rp_drop_no_ff  : std_logic;  -- RCV goes to drop, but does not assert force free,
+                  -- so TP won't wait for force free to be done. E.g. when memory is full
+                  -- and we don't have allocated pages -> RCV drops, but no pages used so
+                  -- no force free.
+
  -- Signals written by rcv_pck FSM and used by ll_write FSM, sync by rtu_rsp_ack
  signal rp_ll_entry_addr     : std_logic_vector(g_page_addr_width - 1 downto 0);
  signal rp_ll_entry_size     : std_logic_vector(c_page_size_width - 1 downto 0);
@@ -823,6 +828,7 @@ begin  --archS_PCKSTART_SET_AND_REQ
            in_pck_dvalid_d0  <= '0';
            in_pck_dat_d0     <= (others => '0');
            rtu_rsp_abort_o   <= '0';
+            rp_drop_no_ff     <= '0';

            -- Sync with trasnfer_pck FSM and ll_write FSM: 
            if(lw_sync_first_stage = '1' and tp_sync = '1') then
@@ -872,6 +878,7 @@ begin  --archS_PCKSTART_SET_AND_REQ
              
              if(tp_drop = '1') then
                s_rcv_pck         <= S_DROP;
+                rp_drop_no_ff     <= '1';
                snk_stall_force_l <= '0';
              else
                current_pckstart_pageaddr <= pckstart_pageaddr;
@@ -1860,6 +1867,10 @@ begin
          -- for global sync
          elsif(mmu_force_free_req = '1' and mmu_force_free_done_i = '1') then
            s_transfer_pck <= S_IDLE;  
+          -- we got here when RCV FSM did not use any page (memory was full), so we don't wait
+          -- for  force_free_done, because it will never happen.
+          elsif(rp_drop_no_ff = '1') then
+            s_transfer_pck <= S_IDLE;
          end if;

          --===========================================================================================