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SubjectRe: [PATCH v8 04/26] PM / Domains: Add support for CPU devices to genpd
On Fri, Aug 3, 2018 at 1:43 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On 19 July 2018 at 12:25, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>> On Wednesday, June 20, 2018 7:22:04 PM CEST Ulf Hansson wrote:
>>> To enable a device belonging to a CPU to be attached to a PM domain managed
>>> by genpd, let's do a few changes to genpd as to make it convenient to
>>> manage the specifics around CPUs.
>>>
>>> First, as to be able to quickly find out what CPUs that are attached to a
>>> genpd, which typically becomes useful from a genpd governor as following
>>> changes is about to show, let's add a cpumask 'cpus' to the struct
>>> generic_pm_domain.
>>>
>>> At the point when a device that belongs to a CPU, is attached/detached to
>>> its corresponding PM domain via genpd_add_device(), let's update the
>>> cpumask in genpd->cpus. Moreover, propagate the update of the cpumask to
>>> the master domains, which makes the genpd->cpus to contain a cpumask that
>>> hierarchically reflect all CPUs for a genpd, including CPUs attached to
>>> subdomains.
>>>
>>> Second, to unconditionally manage CPUs and the cpumask in genpd->cpus, is
>>> unnecessary for cases when only non-CPU devices are parts of a genpd.
>>> Let's avoid this by adding a new configuration bit, GENPD_FLAG_CPU_DOMAIN.
>>> Clients must set the bit before they call pm_genpd_init(), as to instruct
>>> genpd that it shall deal with CPUs and thus manage the cpumask in
>>> genpd->cpus.
>>>
>>> Cc: Lina Iyer <ilina@codeaurora.org>
>>> Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
>>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>>> ---
>>> drivers/base/power/domain.c | 69 ++++++++++++++++++++++++++++++++++++-
>>> include/linux/pm_domain.h | 3 ++
>>> 2 files changed, 71 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>>> index 21d298e1820b..6149ce0bfa7b 100644
>>> --- a/drivers/base/power/domain.c
>>> +++ b/drivers/base/power/domain.c
>>> @@ -20,6 +20,7 @@
>>> #include <linux/sched.h>
>>> #include <linux/suspend.h>
>>> #include <linux/export.h>
>>> +#include <linux/cpu.h>
>>>
>>> #include "power.h"
>>>
>>> @@ -126,6 +127,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
>>> #define genpd_is_irq_safe(genpd) (genpd->flags & GENPD_FLAG_IRQ_SAFE)
>>> #define genpd_is_always_on(genpd) (genpd->flags & GENPD_FLAG_ALWAYS_ON)
>>> #define genpd_is_active_wakeup(genpd) (genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
>>> +#define genpd_is_cpu_domain(genpd) (genpd->flags & GENPD_FLAG_CPU_DOMAIN)
>>>
>>> static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
>>> const struct generic_pm_domain *genpd)
>>> @@ -1377,6 +1379,62 @@ static void genpd_free_dev_data(struct device *dev,
>>> dev_pm_put_subsys_data(dev);
>>> }
>>>
>>> +static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
>>> + int cpu, bool set, unsigned int depth)
>>> +{
>>> + struct gpd_link *link;
>>> +
>>> + if (!genpd_is_cpu_domain(genpd))
>>> + return;
>>> +
>>> + list_for_each_entry(link, &genpd->slave_links, slave_node) {
>>> + struct generic_pm_domain *master = link->master;
>>> +
>>> + genpd_lock_nested(master, depth + 1);
>>> + __genpd_update_cpumask(master, cpu, set, depth + 1);
>>> + genpd_unlock(master);
>>> + }
>>> +
>>> + if (set)
>>> + cpumask_set_cpu(cpu, genpd->cpus);
>>> + else
>>> + cpumask_clear_cpu(cpu, genpd->cpus);
>>> +}
>>
>> As noted elsewhere, there is a concern about the possible weight of this
>> cpumask and I think that it would be good to explicitly put a limit on it.
>
> I have been digesting your comments on the series, but wonder if this
> is still a relevant concern?

Well, there are systems with very large cpumasks and it is sort of
good to have that in mind when designing any code using them.

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