[PATCH v2 1/7] pmdomain: core: Enable s2idle for CPU PM domains on PREEMPT_RT

Ulf Hansson
2024-05-27T14:26:11Z

To allow a genpd provider for a CPU PM domain to enter a domain-idle-state
during s2idle on a PREEMPT_RT based configuration, we can't use the regular
spinlock, as they are turned into sleepable locks on PREEMPT_RT.

To address this problem, let's convert into using the raw spinlock, but
only for genpd providers that have the GENPD_FLAG_CPU_DOMAIN bit set. In
this way, the lock can still be acquired/released in atomic context, which
is needed in the idle-path for PREEMPT_RT.

Do note that the genpd power-on/off notifiers may also be fired during
s2idle, but these are already prepared for PREEMPT_RT as they are based on
the raw notifiers. However, consumers of them may need to adopt accordingly
to work properly on PREEMPT_RT.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---

Changes in v2:
- None.

---
drivers/pmdomain/core.c | 47 ++++++++++++++++++++++++++++++++++++++-
include/linux/pm_domain.h | 5 ++++-
2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index 623d15b68707..072e6bdb6ee6 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -117,6 +117,48 @@ static const struct genpd_lock_ops genpd_spin_ops = {
.unlock = genpd_unlock_spin,
};

+static void genpd_lock_raw_spin(struct generic_pm_domain *genpd)
+ __acquires(&genpd->raw_slock)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&genpd->raw_slock, flags);
+ genpd->raw_lock_flags = flags;
+}
+
+static void genpd_lock_nested_raw_spin(struct generic_pm_domain *genpd,
+ int depth)
+ __acquires(&genpd->raw_slock)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave_nested(&genpd->raw_slock, flags, depth);
+ genpd->raw_lock_flags = flags;
+}
+
+static int genpd_lock_interruptible_raw_spin(struct generic_pm_domain *genpd)
+ __acquires(&genpd->raw_slock)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&genpd->raw_slock, flags);
+ genpd->raw_lock_flags = flags;
+ return 0;
+}
+
+static void genpd_unlock_raw_spin(struct generic_pm_domain *genpd)
+ __releases(&genpd->raw_slock)
+{
+ raw_spin_unlock_irqrestore(&genpd->raw_slock, genpd->raw_lock_flags);
+}
+
+static const struct genpd_lock_ops genpd_raw_spin_ops = {
+ .lock = genpd_lock_raw_spin,
+ .lock_nested = genpd_lock_nested_raw_spin,
+ .lock_interruptible = genpd_lock_interruptible_raw_spin,
+ .unlock = genpd_unlock_raw_spin,
+};
+
#define genpd_lock(p) p->lock_ops->lock(p)
#define genpd_lock_nested(p, d) p->lock_ops->lock_nested(p, d)
#define genpd_lock_interruptible(p) p->lock_ops->lock_interruptible(p)
@@ -2079,7 +2121,10 @@ static void genpd_free_data(struct generic_pm_domain *genpd)

static void genpd_lock_init(struct generic_pm_domain *genpd)
{
- if (genpd->flags & GENPD_FLAG_IRQ_SAFE) {
+ if (genpd->flags & GENPD_FLAG_CPU_DOMAIN) {
+ raw_spin_lock_init(&genpd->raw_slock);
+ genpd->lock_ops = &genpd_raw_spin_ops;
+ } else if (genpd->flags & GENPD_FLAG_IRQ_SAFE) {
spin_lock_init(&genpd->slock);
genpd->lock_ops = &genpd_spin_ops;
} else {
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index f24546a3d3db..0d7fc47de3bc 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -194,8 +194,11 @@ struct generic_pm_domain {
spinlock_t slock;
unsigned long lock_flags;
};
+ struct {
+ raw_spinlock_t raw_slock;
+ unsigned long raw_lock_flags;
+ };
};
-
};

static inline struct generic_pm_domain *pd_to_genpd(struct dev_pm_domain *pd)
--
2.34.1