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Fix bus stall getting stuck high when a bus fault exception isn't immediately accepted by the frontend

This commit is contained in:
Luke Wren 2021-12-06 19:28:21 +00:00
parent 50d3d5d3b3
commit ed22d502fd
1 changed files with 5 additions and 1 deletions
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6
hdl/hazard3_core.v
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@ -766,7 +766,11 @@ assign f_jump_req = x_jump_req || m_trap_enter_vld;
assign f_jump_target = m_trap_enter_vld ? m_trap_addr : x_jump_target;
assign x_jump_not_except = !m_trap_enter_vld;
wire m_bus_stall = xm_memop != MEMOP_NONE && !bus_dph_ready_d && !(
// EXCEPT_NONE clause is needed in the following sequence:
// - Cycle 0: hresp asserted, hready low. We set the exception to squash behind us. Bus stall high.
// - Cycle 1: hready high. For whatever reason, the frontend can't accept the trap address this cycle.
// - Cycle 2: Our dataphase has ended, so bus_dph_ready_d doesn't pulse again. m_bus_stall stuck high.
wire m_bus_stall = xm_memop != MEMOP_NONE && !bus_dph_ready_d && xm_except == EXCEPT_NONE && !(
|EXTENSION_A && xm_memop == MEMOP_SC_W && !mw_local_exclusive_reserved
);