[RFC PATCH 5/8] arm64: parse cpu capacity from DT

Dietmar Eggemann
2015-12-10T14:15:00Z

On 23/11/15 14:28, Juri Lelli wrote:
> With the introduction of cpu capacity bindings, CPU capacities can now be
> extracted from DT. Add parsing of such information at boot time. Also,
> store such information using per CPU variables, as we do for arm.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Mark Brown <broonie@linaro.org>
> Cc: Sudeep Holla <sudeep.holla@arm.com>
> Signed-off-by: Juri Lelli <juri.lelli@arm.com>
> ---
> arch/arm64/kernel/topology.c | 46 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 46 insertions(+)

A lot of code disappears if you get rid of capacity-scale.

>
> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> index 694f6de..4423cc5 100644
> --- a/arch/arm64/kernel/topology.c
> +++ b/arch/arm64/kernel/topology.c
> @@ -23,6 +23,45 @@
> #include <asm/cputype.h>
> #include <asm/topology.h>
>
> +static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
> +
> +unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
> +{
> + return per_cpu(cpu_scale, cpu);
> +}
> +
> +static void set_capacity_scale(unsigned int cpu, unsigned long capacity)
> +{
> + per_cpu(cpu_scale, cpu) = capacity;
> +}
> +
> +static u32 capacity_scale = SCHED_CAPACITY_SCALE;
> +
> +static void __init parse_cpu_capacity(struct device_node *cpu_node, int cpu)
> +{
> + int ret;
> + u32 cpu_capacity;
> +
> + ret = of_property_read_u32(cpu_node,
> + "capacity",
> + &cpu_capacity);
> + if (!ret) {
> + u64 capacity;
> +
> + /*
> + * Enforce capacity <= capacity-scale.
> + */
> + cpu_capacity = cpu_capacity <= capacity_scale ? cpu_capacity :
> + capacity_scale;
> + capacity = (cpu_capacity << SCHED_CAPACITY_SHIFT) /
> + capacity_scale;
> +
> + set_capacity_scale(cpu, capacity);
> + pr_info("CPU%d: DT cpu_capacity %lu\n",
> + cpu, arch_scale_cpu_capacity(NULL, cpu));
> + }
> +}
> +
> static int __init get_cpu_for_node(struct device_node *node)
> {
> struct device_node *cpu_node;
> @@ -34,6 +73,7 @@ static int __init get_cpu_for_node(struct device_node *node)
>
> for_each_possible_cpu(cpu) {
> if (of_get_cpu_node(cpu, NULL) == cpu_node) {
> + parse_cpu_capacity(cpu_node, cpu);
> of_node_put(cpu_node);
> return cpu;
> }
> @@ -173,6 +213,12 @@ static int __init parse_dt_topology(void)
> return 0;
> }
>
> + if (!of_property_read_u32(cn, "capacity-scale", &capacity_scale))
> + pr_info("DT cpus capacity-scale %u\n", capacity_scale);
> + else
> + pr_debug("DT cpus capacity-scale not found: assuming %u\n",
> + capacity_scale);
> +
> /*
> * When topology is provided cpu-map is essentially a root
> * cluster with restricted subnodes.
>