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The GenericTimer specification includes a global component for a universal view of time: the System Counter. If both per-PE architected and memory-mapped timers are instantiated in a system, they must both share the same counter. SystemCounter is promoted to be an independent SimObject, which is now shared by implementations. The SystemCounter may be controlled/accessed through the memory-mapped counter module in the system level implementation. This provides control (CNTControlBase) and status (CNTReadBase) register frames. The counter module is now implemented as part of GenericTimerMem. Frequency changes occur through writes to an active CNTFID or to CNTCR.EN as per the architecture. Low-high and high-low transitions are delayed until suitable thresholds, where the counter value is a divisor of the increment given the new frequency. Due to changes in frequency, timers need to be notifies to be rescheduled their counter limit events based on CompareValue/TimerValue. A new SystemCounterListener interface is provided to achieve correctness. CNTFRQ is no longer able to modify the global frequency. PEs may use this to modify their register view of the former, but they should not affect the global value. These two should be consistent. With frequency changes, counter value needs to be stored to track contributions from different frequency epochs. This is now handled on epoch change, counter disable and register access. References to all GenericTimer model components are now provided as part of the documentation. VExpress_GEM5_Base is updated with the new model configuration. Change-Id: I9a991836cacd84a5bc09e5d5275191fcae9ed84b Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25306 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
This is the gem5 simulator. The main website can be found at http://www.gem5.org A good starting point is http://www.gem5.org/about, and for more information about building the simulator and getting started please see http://www.gem5.org/documentation and http://www.gem5.org/documentation/learning_gem5/introduction. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, SWIG, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/documentation/general_docs/building for more details concerning the minimum versions of the aforementioned tools. Once you have all dependencies resolved, type 'scons build/<ARCH>/gem5.opt' where ARCH is one of ARM, NULL, MIPS, POWER, SPARC, or X86. This will build an optimized version of the gem5 binary (gem5.opt) for the the specified architecture. See http://www.gem5.org/documentation/general_docs/building for more details and options. The basic source release includes these subdirectories: - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - src: source code of the gem5 simulator - system: source for some optional system software for simulated systems - tests: regression tests - util: useful utility programs and files To run full-system simulations, you will need compiled system firmware (console and PALcode for Alpha), kernel binaries and one or more disk images. If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.