modules/swcore: prevent losing a page when dropping on pages boundary

When it turns out we have to drop frame (e.g. because memory is full) and we get this information on page boundary, next inter page is already being requested. However, we do not use previously allocated inter page, that means we lose previously allocated page forever. In most of the cases, the conditional statement prevents such situation by checking mpm_dlast = '0'. But mpm_dlast is delayed by 1 clock cycle, that's why I added checking for tp_drop. Now, if we get in the same cycle mpm_pg_req and tp_drop, then we don't make a new inter page request.

modules/swcore: prevent losing a page when dropping on pages boundary
When it turns out we have to drop frame (e.g. because memory is full) and we get this information on page boundary, next inter page is already being requested. However, we do not use previously allocated inter page, that means we lose previously allocated page forever. In most of the cases, the conditional statement prevents such situation by checking mpm_dlast = '0'. But mpm_dlast is delayed by 1 clock cycle, that's why I added checking for tp_drop. Now, if we get in the same cycle mpm_pg_req and tp_drop, then we don't make a new inter page request.
dd0dadd6 · Grzegorz Daniluk · cfe50f15 · dd0dadd6
Commit dd0dadd6 authored Mar 30, 2015 by Grzegorz Daniluk
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xswc_input_block.vhd modules/wrsw_swcore/xswc_input_block.vhd +1 -1

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--- a/modules/wrsw_swcore/xswc_input_block.vhd
+++ b/modules/wrsw_swcore/xswc_input_block.vhd
@@ -1192,7 +1192,7 @@ begin
        pckstart_page_in_advance <= '1';
      end if;

-      if(mpm_pg_req_i = '1' and mpm_dlast = '0') then
+      if(mpm_pg_req_i = '1' and mpm_dlast = '0' and tp_drop = '0') then
        pckinter_page_in_advance <= '0';
      elsif(mmu_page_alloc_done_i = '1' and pckinter_page_alloc_req = '1') then
        pckinter_page_in_advance <= '1';