riscv/rocket-chip
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Fix mapping of acquire/release AMOs to fence operations

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AMO.aq should be implemented as AMO;FENCE, whereas AMO.rl should be
implemented as FENCE;AMO.  These had been swapped.  This error does
not affect cacheable accesses using the blocking D$, nor does it
affect accesses to the data scratchpad, nor does it affect accesses
to strongly ordered I/O regions (which is the default).

Cacheable accesses using the nonblocking D$ and accesses to weakly
ordered I/O regions may manifest memory-ordering violations.  For
these accesses, the workaround is to use AMO.aqrl whenever AMO.aq
or AMO.rl had been used.
This commit is contained in:
Andrew Waterman 2018-02-23 16:39:47 -08:00
parent 95294bbdcb
commit eb6e192ec0
1 changed files with 3 additions and 3 deletions
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6
src/main/scala/rocket/RocketCore.scala
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@ -210,17 +210,17 @@ class Rocket(implicit p: Parameters) extends CoreModule()(p)
id_ctrl.rocc && csr.io.decode(0).rocc_illegal ||
id_csr_en && (csr.io.decode(0).read_illegal || !id_csr_ren && csr.io.decode(0).write_illegal) ||
!ibuf.io.inst(0).bits.rvc && ((id_sfence || id_system_insn) && csr.io.decode(0).system_illegal)
// stall decode for fences (now, for AMO.aq; later, for AMO.rl and FENCE)
// stall decode for fences (now, for AMO.rl; later, for AMO.aq and FENCE)
val id_amo_aq = id_inst(0)(26)
val id_amo_rl = id_inst(0)(25)
val id_fence_next = id_ctrl.fence || id_ctrl.amo && id_amo_rl
val id_fence_next = id_ctrl.fence || id_ctrl.amo && id_amo_aq
val id_mem_busy = !io.dmem.ordered || io.dmem.req.valid
when (!id_mem_busy) { id_reg_fence := false }
val id_rocc_busy = Bool(usingRoCC) &&
(io.rocc.busy || ex_reg_valid && ex_ctrl.rocc ||
mem_reg_valid && mem_ctrl.rocc || wb_reg_valid && wb_ctrl.rocc)
val id_do_fence = Wire(init = id_rocc_busy && id_ctrl.fence ||
id_mem_busy && (id_ctrl.amo && id_amo_aq || id_ctrl.fence_i || id_reg_fence && (id_ctrl.mem || id_ctrl.rocc)))
id_mem_busy && (id_ctrl.amo && id_amo_rl || id_ctrl.fence_i || id_reg_fence && (id_ctrl.mem || id_ctrl.rocc)))
val bpu = Module(new BreakpointUnit(nBreakpoints))
bpu.io.status := csr.io.status