mem: Add precharge all (PREA) to the DRAM controller

This patch adds the basic ingredients for a precharge all operation,
to be used in conjunction with DRAM power modelling.

Currently we do not try and apply any cleverness when precharging all
banks, thus even if only a single bank is open we use PREA as opposed
to PRE. At the moment we only have a single tRP (tRPpb), and do not
model the slightly longer all-bank precharge constraint (tRPab).
This commit is contained in:
Andreas Hansson 2014-05-09 18:58:48 -04:00
parent 0ba1e72e9b
commit 8e3869411d

View file

@ -850,6 +850,9 @@ DRAMCtrl::prechargeBank(Bank& bank, Tick pre_at)
bank.openRow = Bank::NO_ROW; bank.openRow = Bank::NO_ROW;
// no precharge allowed before this one
bank.preAllowedAt = pre_at;
Tick pre_done_at = pre_at + tRP; Tick pre_done_at = pre_at + tRP;
bank.actAllowedAt = std::max(bank.actAllowedAt, pre_done_at); bank.actAllowedAt = std::max(bank.actAllowedAt, pre_done_at);
@ -1305,16 +1308,34 @@ DRAMCtrl::processRefreshEvent()
// precharge any active bank if we are not already in the idle // precharge any active bank if we are not already in the idle
// state // state
if (pwrState != PWR_IDLE) { if (pwrState != PWR_IDLE) {
// at the moment, we use a precharge all even if there is
// only a single bank open
DPRINTF(DRAM, "Precharging all\n"); DPRINTF(DRAM, "Precharging all\n");
// first determine when we can precharge
Tick pre_at = curTick();
for (int i = 0; i < ranksPerChannel; i++) {
for (int j = 0; j < banksPerRank; j++) {
// respect both causality and any existing bank
// constraints, some banks could already have a
// (auto) precharge scheduled
pre_at = std::max(banks[i][j].preAllowedAt, pre_at);
}
}
// make sure all banks are precharged, and for those that
// already are, update their availability
Tick act_allowed_at = pre_at + tRP;
for (int i = 0; i < ranksPerChannel; i++) { for (int i = 0; i < ranksPerChannel; i++) {
for (int j = 0; j < banksPerRank; j++) { for (int j = 0; j < banksPerRank; j++) {
if (banks[i][j].openRow != Bank::NO_ROW) { if (banks[i][j].openRow != Bank::NO_ROW) {
// respect both causality and any existing bank
// constraints
Tick pre_at = std::max(banks[i][j].preAllowedAt,
curTick());
prechargeBank(banks[i][j], pre_at); prechargeBank(banks[i][j], pre_at);
} else {
banks[i][j].actAllowedAt =
std::max(banks[i][j].actAllowedAt, act_allowed_at);
banks[i][j].preAllowedAt =
std::max(banks[i][j].preAllowedAt, pre_at);
} }
} }
} }