| Message ID | 1477469071-2282-1-git-send-email-noamca@mellanox.com |
|---|---|
| State | New |
| Headers | show |
On 10/26/2016 01:04 AM, Noam Camus wrote: > From: Noam Camus <noamca@mellanox.com> > > Today we use smp_init_cpus() to set cpu possible mask > and we use smp_prepare_cpus() to set cpu present mask. > For possible mask we use all CPUs at range [0-NR_CPUS] and > for present mask we use all CPUs at range [0-max_cpus] > which is actually the same as possible mask (no hutplug). > > For platform like eznps we wish to have more configurable range then > being statically defined by NR_CPUS (actuall derived from CONFIG_NR_CPUS). > For this purpose we added two new entries at our device tree root level: > possible-cpus > present-cpus > > The format of this new entries is same like for all similar kernel > parameters which provide cpu list (see Documentation/kernel-parameters.txt) > example of use would be (assume CONFIG_NR_CPUS=8): > present-cpus = "0-1,6-7"; > possible-cpus = "0-7"; > > Now if we provide such list in our DT then we won't use the statically range. > In our example above only CPUs 0,1,6,7 will be up after boot. > > Signed-off-by: Noam Camus <noamca@mellanox.com> > --- > arch/arc/kernel/smp.c | 32 ++++++++++++++++++++++++++++---- > 1 files changed, 28 insertions(+), 4 deletions(-) > > diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c > index 03d5151..5855403 100644 > --- a/arch/arc/kernel/smp.c > +++ b/arch/arc/kernel/smp.c > @@ -16,6 +16,7 @@ > #include <linux/sched.h> > #include <linux/interrupt.h> > #include <linux/profile.h> > +#include <linux/of_fdt.h> > #include <linux/mm.h> > #include <linux/cpu.h> > #include <linux/irq.h> > @@ -34,6 +35,21 @@ arch_spinlock_t smp_bitops_lock = __ARCH_SPIN_LOCK_UNLOCKED; > > struct plat_smp_ops __weak plat_smp_ops; > > +/* Get CPUs mask from device tree */ > +static int __init smp_get_cpumask(const char *name, struct cpumask *cpumask) > +{ > + unsigned long dt_root = of_get_flat_dt_root(); > + const char *buf; > + > + buf = of_get_flat_dt_prop(dt_root, name, NULL); > + if (!buf) > + return 0; > + > + cpulist_parse(buf, cpumask); > + > + return 1; > +} > + > /* XXX: per cpu ? Only needed once in early seconday boot */ > struct task_struct *secondary_idle_tsk; > > @@ -54,9 +70,13 @@ void __init smp_prepare_boot_cpu(void) > void __init smp_init_cpus(void) > { > unsigned int i; > + struct cpumask cpumask; > > - for (i = 0; i < NR_CPUS; i++) > - set_cpu_possible(i, true); > + if (smp_get_cpumask("possible-cpus", &cpumask)) > + init_cpu_possible(&cpumask); > + else > + for (i = 0; i < NR_CPUS; i++) > + set_cpu_possible(i, true); This is not checkpatch clean, need to enclose the if / else in { } Anyhow, it seems we don't need this as ARC set_cpu_possible() will be overridden by your init_early_smp() hook anyways ? We don't need to generalize it as I don't foresee other platforms needing it. > > if (plat_smp_ops.init_early_smp) > plat_smp_ops.init_early_smp(); > @@ -66,13 +86,17 @@ void __init smp_init_cpus(void) > void __init smp_prepare_cpus(unsigned int max_cpus) > { > int i; > + struct cpumask cpumask; > > /* > * Initialise the present map, which describes the set of CPUs > * actually populated at the present time. > */ > - for (i = 0; i < max_cpus; i++) > - set_cpu_present(i, true); > + if (smp_get_cpumask("present-cpus", &cpumask)) > + init_cpu_present(&cpumask); > + else > + for (i = 0; i < max_cpus; i++) > + set_cpu_present(i, true); > } With the existing DT based cpu bitmap setting in your platform code, can we instead do something like below in smp_prepare_cpus(): if (num_present_cpus() <= 1) { /* boot already marked present in init/main.c */ for (i = 0; i < max_cpus; i++) set_cpu_present(i, true); } So to summarize you keep the existing DT based cpu bitmap settings in your platform code and just add one workaround to not over-ride present map in ARC common code. -Vineet
diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c index 03d5151..5855403 100644 --- a/arch/arc/kernel/smp.c +++ b/arch/arc/kernel/smp.c @@ -16,6 +16,7 @@ #include <linux/sched.h> #include <linux/interrupt.h> #include <linux/profile.h> +#include <linux/of_fdt.h> #include <linux/mm.h> #include <linux/cpu.h> #include <linux/irq.h> @@ -34,6 +35,21 @@ arch_spinlock_t smp_bitops_lock = __ARCH_SPIN_LOCK_UNLOCKED; struct plat_smp_ops __weak plat_smp_ops; +/* Get CPUs mask from device tree */ +static int __init smp_get_cpumask(const char *name, struct cpumask *cpumask) +{ + unsigned long dt_root = of_get_flat_dt_root(); + const char *buf; + + buf = of_get_flat_dt_prop(dt_root, name, NULL); + if (!buf) + return 0; + + cpulist_parse(buf, cpumask); + + return 1; +} + /* XXX: per cpu ? Only needed once in early seconday boot */ struct task_struct *secondary_idle_tsk; @@ -54,9 +70,13 @@ void __init smp_prepare_boot_cpu(void) void __init smp_init_cpus(void) { unsigned int i; + struct cpumask cpumask; - for (i = 0; i < NR_CPUS; i++) - set_cpu_possible(i, true); + if (smp_get_cpumask("possible-cpus", &cpumask)) + init_cpu_possible(&cpumask); + else + for (i = 0; i < NR_CPUS; i++) + set_cpu_possible(i, true); if (plat_smp_ops.init_early_smp) plat_smp_ops.init_early_smp(); @@ -66,13 +86,17 @@ void __init smp_init_cpus(void) void __init smp_prepare_cpus(unsigned int max_cpus) { int i; + struct cpumask cpumask; /* * Initialise the present map, which describes the set of CPUs * actually populated at the present time. */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + if (smp_get_cpumask("present-cpus", &cpumask)) + init_cpu_present(&cpumask); + else + for (i = 0; i < max_cpus; i++) + set_cpu_present(i, true); } void __init smp_cpus_done(unsigned int max_cpus)