Re: [RFC] Add Arm cpu topology definition

On 06/16/2011 01:49 AM, Vincent Guittot wrote:

+config SCHED_MC

• bool "Multi-core scheduler support"
• depends on SMP && ARM_CPU_TOPOLOGY
• default n
• help

•  Multi-core scheduler support improves the CPU scheduler's decision
  

•  making when dealing with multi-core CPU chips at a cost of slightly
  

•  increased overhead in some places. If unsure say N here.
  

+config SCHED_SMT

• bool "SMT scheduler support"
• depends on SMP && ARM_CPU_TOPOLOGY
• default n
• help

•  Improves the CPU scheduler's decision making when dealing with
  

•  MultiThreading at a cost of slightly increased overhead in some
  

•  places. If unsure say N here.
  

The default is already n so you can drop those two lines.

•  * This is a multiprocessor system
  

•  * multiprocessor format & multiprocessor mode field are set
  

•  */
  

• if (mpidr & (0x1 << 24)) {
  

• 	/* core performance interdependency */
  

• 	cpuid_topo->thread_id = (mpidr & 0x3);
  

• 	cpuid_topo->core_id =  ((mpidr >> 8) & 0xF);
  

• 	cpuid_topo->socket_id = ((mpidr >> 16) & 0xFF);
  

• } else {
  

• 	/* normal core interdependency */
  

• 	cpuid_topo->thread_id = -1;
  

• 	cpuid_topo->core_id = (mpidr & 0x3);
  

• 	cpuid_topo->socket_id = ((mpidr >> 8) & 0xF);
  

• }
  

The ARM ARM says these fields are IMPLEMENTATION DEFINED meaning that different vendors may attribute different meaning to these fields if they wish. Does that mean this should be a platform_*() function?