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mem: Fix a bug in the DRAM controller arbitration

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Fix a minor issue that affects multi-rank systems.
This commit is contained in:
Omar Naji 2014-12-23 09:31:18 -05:00
parent e76e8e28a3
commit 152c02354e
1 changed files with 9 additions and 3 deletions
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12
src/mem/dram_ctrl.cc
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@ -1477,7 +1477,13 @@ DRAMCtrl::minBankPrep(const deque<DRAMPacket*>& queue,
// Offset by tRCD to correlate with ACT timing variables // Offset by tRCD to correlate with ACT timing variables
Tick min_cmd_at = busBusyUntil - tCL - tRCD; 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 // Only optimize for same ranks when the command type
// does not change; do not want to unnecessarily incur tWTR // does not change; do not want to unnecessarily incur tWTR
// //
@ -1485,8 +1491,8 @@ DRAMCtrl::minBankPrep(const deque<DRAMPacket*>& queue,
// 1) Commands that access the same rank as previous burst // 1) Commands that access the same rank as previous burst
// and can prep the bank seamlessly. // and can prep the bank seamlessly.
// 2) Commands (any rank) with earliest bank prep // 2) Commands (any rank) with earliest bank prep
if (!switched_cmd_type && same_rank_match && if ((bank_mask == 0) || (!switched_cmd_type && same_rank_match &&
min_act_at_same_rank <= min_cmd_at) { min_act_at_same_rank <= min_cmd_at)) {
bank_mask = bank_mask_same_rank; bank_mask = bank_mask_same_rank;
} }