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



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