From 152c02354ee53f4f4f10ac01911eb92386ef6fd2 Mon Sep 17 00:00:00 2001 From: Omar Naji Date: Tue, 23 Dec 2014 09:31:18 -0500 Subject: [PATCH] mem: Fix a bug in the DRAM controller arbitration Fix a minor issue that affects multi-rank systems. --- src/mem/dram_ctrl.cc | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/src/mem/dram_ctrl.cc b/src/mem/dram_ctrl.cc index 8378debf1..62ae9e984 100644 --- a/src/mem/dram_ctrl.cc +++ b/src/mem/dram_ctrl.cc @@ -1477,7 +1477,13 @@ DRAMCtrl::minBankPrep(const deque& queue, // Offset by tRCD to correlate with ACT timing variables Tick min_cmd_at = busBusyUntil - tCL - tRCD; - // Prioritize same rank accesses that can issue B2B + // if we have multiple ranks and all + // waiting packets are accessing a rank which was previously active + // then bank_mask_same_rank will be set to a value while bank_mask will + // remain 0. In this case, the function should return the value of + // bank_mask_same_rank. + // else if waiting packets access a rank which was previously active and + // other ranks, prioritize same rank accesses that can issue B2B // Only optimize for same ranks when the command type // does not change; do not want to unnecessarily incur tWTR // @@ -1485,8 +1491,8 @@ DRAMCtrl::minBankPrep(const deque& queue, // 1) Commands that access the same rank as previous burst // and can prep the bank seamlessly. // 2) Commands (any rank) with earliest bank prep - if (!switched_cmd_type && same_rank_match && - min_act_at_same_rank <= min_cmd_at) { + if ((bank_mask == 0) || (!switched_cmd_type && same_rank_match && + min_act_at_same_rank <= min_cmd_at)) { bank_mask = bank_mask_same_rank; } -- 2.30.2