mem: Add an HBM memory controller

This change adds an hbm memory controller in gem5,
which is capable of controlling two hbm memory interfaces
(two pseudo channels). HBMCtrl inherits from MemCtrl
and tries to reuse most of the MemCtrl functions for two
different dram interfaces. Morever, a notion of pseudo
channel is added in the memory interface itself, to make
sure that the scheduling decisions in any interface are
based on the pkts for that pseudo channel only. Also, the
command bandwidth checks are divided into row and column
commands, which are shared by both pseudo channels.

Change-Id: Ie2ee8183d0f7f744aff2ed05cabc75fec3ea2171
Reviewed-by: Jason Lowe-Power <>
Maintainer: Jason Lowe-Power <>
Reviewed-by: Wendy Elsasser <>
Tested-by: kokoro <>
14 files changed