The cpu-map DT entry in ARM can describe the CPU topology in much better way compared to other existing approaches. RISC-V can easily adopt this binding to represent its own CPU topology. Thus, both cpu-map DT binding and topology parsing code can be moved to a common location so that RISC-V or any other architecture can leverage that.
The relevant discussion regarding unifying cpu topology can be found in [1]. arch_topology seems to be a perfect place to move the common code. I have not introduced any significant functional changes in the moved code. The only downside in this approach is that the capacity code will be executed for RISC-V as well. But, it will exit immediately after not able to find the appropriate DT node. If the overhead is considered too much, we can always compile out capacity related functions under a different config for the architectures that do not support them. There was an opportunity to unify topology data structure for ARM32 done by patch 3/4. But, I refrained from making any other changes as I am not very well versed with original intention for some functions that are present in arch_topology.c. I hope this patch series can be served as a baseline for such changes in the future. The patches have been tested for RISC-V and compile tested for ARM64, ARM32 & x86. The socket change[2] is also now part of this series. [1] https://lkml.org/lkml/2018/11/6/19 [2] https://lkml.org/lkml/2018/11/7/918 QEMU changes for RISC-V topology are available at https://github.com/atishp04/qemu/tree/riscv_topology_dt HiFive Unleashed DT with topology node is available here. https://github.com/atishp04/opensbi/tree/HiFive_unleashed_topology It can be verified with OpenSBI with following additional compile time option. FW_PAYLOAD_FDT="unleashed_topology.dtb" Changes from v3->v4 1. Get rid of ARM32 specific information in topology strucuture. 2. Remove redundant functions from ARM32 and use common code instead. Changes from v2->v3 1. Cover letter update with experiment DT for topology changes. 2. Added the patch for [2]. Changes from v1->v2 1. ARM32 can now use the common code as well. Atish Patra (4): dt-binding: cpu-topology: Move cpu-map to a common binding. cpu-topology: Move cpu topology code to common code. arm: Use common cpu_topology structure and functions. RISC-V: Parse cpu topology during boot. Sudeep Holla (1): Documentation: DT: arm: add support for sockets defining package boundaries .../topology.txt => cpu/cpu-topology.txt} | 134 ++++++-- arch/arm/include/asm/topology.h | 20 -- arch/arm/kernel/topology.c | 60 +--- arch/arm64/include/asm/topology.h | 23 -- arch/arm64/kernel/topology.c | 303 +----------------- arch/riscv/Kconfig | 1 + arch/riscv/kernel/smpboot.c | 3 + drivers/base/arch_topology.c | 300 ++++++++++++++++- drivers/base/topology.c | 1 + include/linux/arch_topology.h | 26 ++ 10 files changed, 445 insertions(+), 426 deletions(-) rename Documentation/devicetree/bindings/{arm/topology.txt => cpu/cpu-topology.txt} (66%) -- 2.21.0
