[PATCH v6 12/16] firmware: arm_sdei: add support for CPU private events

James Morse
2018-01-08T15:38:14Z

Private SDE events are per-cpu, and need to be registered and enabled
on each CPU.

Hide this detail from the caller by adapting our {,un}register and
{en,dis}able calls to send an IPI to each CPU if the event is private.

CPU private events are unregistered when the CPU is powered-off, and
re-registered when the CPU is brought back online. This saves bringing
secondary cores back online to call private_reset() on shutdown, kexec
and resume from hibernate.

Signed-off-by: James Morse <james.morse-5wv7dgnIgG8@public.gmane.org>
---

Changes since v4:
* rip out the racy frozen flag.
* hotplug hooks honour the event reregister/renable flags instead of
save/restoring the firmware state, these flags are protected by the
spinlock.
* Repurposed the event-enable ipi-call instead of having a redundant
re-enable call.
* Dropped Catalin's ack

drivers/firmware/arm_sdei.c | 206 +++++++++++++++++++++++++++++++++++++++++---
1 file changed, 193 insertions(+), 13 deletions(-)

diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index 0a4c75320840..10a8bfa7339a 100644
--- a/drivers/firmware/arm_sdei.c
+++ b/drivers/firmware/arm_sdei.c
@@ -5,9 +5,11 @@
#include <linux/acpi.h>
#include <linux/arm_sdei.h>
#include <linux/arm-smccc.h>
+#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/compiler.h>
#include <linux/cpuhotplug.h>
+#include <linux/cpu.h>
#include <linux/cpu_pm.h>
#include <linux/errno.h>
#include <linux/hardirq.h>
@@ -52,7 +54,13 @@ struct sdei_event {
u8 priority;

/* This pointer is handed to firmware as the event argument. */
- struct sdei_registered_event *registered;
+ union {
+ /* Shared events */
+ struct sdei_registered_event *registered;
+
+ /* CPU private events */
+ struct sdei_registered_event __percpu *private_registered;
+ };
};

/* Take the mutex for any API call or modification. Take the mutex first. */
@@ -62,6 +70,34 @@ static DEFINE_MUTEX(sdei_events_lock);
static DEFINE_SPINLOCK(sdei_list_lock);
static LIST_HEAD(sdei_list);

+/* Private events are registered/enabled via IPI passing one of these */
+struct sdei_crosscall_args {
+ struct sdei_event *event;
+ atomic_t errors;
+ int first_error;
+};
+
+#define CROSSCALL_INIT(arg, event) (arg.event = event, \
+ arg.first_error = 0, \
+ atomic_set(&arg.errors, 0))
+
+static inline int sdei_do_cross_call(void *fn, struct sdei_event * event)
+{
+ struct sdei_crosscall_args arg;
+
+ CROSSCALL_INIT(arg, event);
+ on_each_cpu(fn, &arg, true);
+
+ return arg.first_error;
+}
+
+static inline void
+sdei_cross_call_return(struct sdei_crosscall_args *arg, int err)
+{
+ if (err && (atomic_inc_return(&arg->errors) == 1))
+ arg->first_error = err;
+}
+
static int sdei_to_linux_errno(unsigned long sdei_err)
{
switch (sdei_err) {
@@ -207,6 +243,26 @@ static struct sdei_event *sdei_event_create(u32 event_num,
reg->callback = cb;
reg->callback_arg = cb_arg;
event->registered = reg;
+ } else {
+ int cpu;
+ struct sdei_registered_event __percpu *regs;
+
+ regs = alloc_percpu(struct sdei_registered_event);
+ if (!regs) {
+ kfree(event);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ for_each_possible_cpu(cpu) {
+ reg = per_cpu_ptr(regs, cpu);
+
+ reg->event_num = event->event_num;
+ reg->priority = event->priority;
+ reg->callback = cb;
+ reg->callback_arg = cb_arg;
+ }
+
+ event->private_registered = regs;
}

if (sdei_event_find(event_num)) {
@@ -232,6 +288,8 @@ static void sdei_event_destroy(struct sdei_event *event)

if (event->type == SDEI_EVENT_TYPE_SHARED)
kfree(event->registered);
+ else
+ free_percpu(event->private_registered);

kfree(event);
}
@@ -262,11 +320,6 @@ static void _ipi_mask_cpu(void *ignored)
sdei_mask_local_cpu();
}

-static int sdei_cpuhp_down(unsigned int ignored)
-{
- return sdei_mask_local_cpu();
-}
-
int sdei_unmask_local_cpu(void)
{
int err;
@@ -288,11 +341,6 @@ static void _ipi_unmask_cpu(void *ignored)
sdei_unmask_local_cpu();
}

-static int sdei_cpuhp_up(unsigned int ignored)
-{
- return sdei_unmask_local_cpu();
-}
-
static void _ipi_private_reset(void *ignored)
{
int err;
@@ -337,6 +385,19 @@ static int sdei_api_event_enable(u32 event_num)
0, NULL);
}

+/* Called directly by the hotplug callbacks */
+static void _local_event_enable(void *data)
+{
+ int err;
+ struct sdei_crosscall_args *arg = data;
+
+ WARN_ON_ONCE(preemptible());
+
+ err = sdei_api_event_enable(arg->event->event_num);
+
+ sdei_cross_call_return(arg, err);
+}
+
int sdei_event_enable(u32 event_num)
{
int err = -EINVAL;
@@ -355,6 +416,8 @@ int sdei_event_enable(u32 event_num)

if (event->type == SDEI_EVENT_TYPE_SHARED)
err = sdei_api_event_enable(event->event_num);
+ else
+ err = sdei_do_cross_call(_local_event_enable, event);
mutex_unlock(&sdei_events_lock);

return err;
@@ -367,6 +430,16 @@ static int sdei_api_event_disable(u32 event_num)
0, 0, NULL);
}

+static void _ipi_event_disable(void *data)
+{
+ int err;
+ struct sdei_crosscall_args *arg = data;
+
+ err = sdei_api_event_disable(arg->event->event_num);
+
+ sdei_cross_call_return(arg, err);
+}
+
int sdei_event_disable(u32 event_num)
{
int err = -EINVAL;
@@ -385,6 +458,8 @@ int sdei_event_disable(u32 event_num)

if (event->type == SDEI_EVENT_TYPE_SHARED)
err = sdei_api_event_disable(event->event_num);
+ else
+ err = sdei_do_cross_call(_ipi_event_disable, event);
mutex_unlock(&sdei_events_lock);

return err;
@@ -397,6 +472,19 @@ static int sdei_api_event_unregister(u32 event_num)
0, 0, 0, NULL);
}

+/* Called directly by the hotplug callbacks */
+static void _local_event_unregister(void *data)
+{
+ int err;
+ struct sdei_crosscall_args *arg = data;
+
+ WARN_ON_ONCE(preemptible());
+
+ err = sdei_api_event_unregister(arg->event->event_num);
+
+ sdei_cross_call_return(arg, err);
+}
+
static int _sdei_event_unregister(struct sdei_event *event)
{
lockdep_assert_held(&sdei_events_lock);
@@ -409,7 +497,7 @@ static int _sdei_event_unregister(struct sdei_event *event)
if (event->type == SDEI_EVENT_TYPE_SHARED)
return sdei_api_event_unregister(event->event_num);

- return -EINVAL;
+ return sdei_do_cross_call(_local_event_unregister, event);
}

int sdei_event_unregister(u32 event_num)
@@ -473,17 +561,50 @@ static int sdei_api_event_register(u32 event_num, unsigned long entry_point,
flags, affinity, NULL);
}

+/* Called directly by the hotplug callbacks */
+static void _local_event_register(void *data)
+{
+ int err;
+ struct sdei_registered_event *reg;
+ struct sdei_crosscall_args *arg = data;
+
+ WARN_ON(preemptible());
+
+ reg = per_cpu_ptr(arg->event->private_registered, smp_processor_id());
+ err = sdei_api_event_register(arg->event->event_num, sdei_entry_point,
+ reg, 0, 0);
+
+ sdei_cross_call_return(arg, err);
+}
+
static int _sdei_event_register(struct sdei_event *event)
{
+ int err;
+
lockdep_assert_held(&sdei_events_lock);

+ spin_lock(&sdei_list_lock);
+ event->reregister = true;
+ spin_unlock(&sdei_list_lock);
+
if (event->type == SDEI_EVENT_TYPE_SHARED)
return sdei_api_event_register(event->event_num,
sdei_entry_point,
event->registered,
SDEI_EVENT_REGISTER_RM_ANY, 0);

- return -EINVAL;
+
+ err = sdei_do_cross_call(_local_event_register, event);
+ if (err) {
+ spin_lock(&sdei_list_lock);
+ event->reregister = false;
+ event->reenable = false;
+ spin_unlock(&sdei_list_lock);
+
+ sdei_do_cross_call(_local_event_unregister, event);
+ }
+
+ return err;
}

int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg)
@@ -538,6 +659,8 @@ static int sdei_reregister_event(struct sdei_event *event)
if (event->reenable) {
if (event->type == SDEI_EVENT_TYPE_SHARED)
err = sdei_api_event_enable(event->event_num);
+ else
+ err = sdei_do_cross_call(_local_event_enable, event);
}

if (err)
@@ -569,6 +692,62 @@ static int sdei_reregister_shared(void)
return err;
}

+static int sdei_cpuhp_down(unsigned int cpu)
+{
+ struct sdei_event *event;
+ struct sdei_crosscall_args arg;
+
+ /* un-register private events */
+ spin_lock(&sdei_list_lock);
+ list_for_each_entry(event, &sdei_list, list) {
+ if (event->type == SDEI_EVENT_TYPE_SHARED)
+ continue;
+
+ CROSSCALL_INIT(arg, event);
+ /* call the cross-call function locally... */
+ _local_event_unregister(&arg);
+ if (arg.first_error)
+ pr_err("Failed to unregister event %u: %d\n",
+ event->event_num, arg.first_error);
+ }
+ spin_unlock(&sdei_list_lock);
+
+ return sdei_mask_local_cpu();
+}
+
+static int sdei_cpuhp_up(unsigned int cpu)
+{
+ struct sdei_event *event;
+ struct sdei_crosscall_args arg;
+
+ /* re-register/enable private events */
+ spin_lock(&sdei_list_lock);
+ list_for_each_entry(event, &sdei_list, list) {
+ if (event->type == SDEI_EVENT_TYPE_SHARED)
+ continue;
+
+ if (event->reregister) {
+ CROSSCALL_INIT(arg, event);
+ /* call the cross-call function locally... */
+ _local_event_register(&arg);
+ if (arg.first_error)
+ pr_err("Failed to re-register event %u: %d\n",
+ event->event_num, arg.first_error);
+ }
+
+ if (event->reenable) {
+ CROSSCALL_INIT(arg, event);
+ _local_event_enable(&arg);
+ if (arg.first_error)
+ pr_err("Failed to re-enable event %u: %d\n",
+ event->event_num, arg.first_error);
+ }
+ }
+ spin_unlock(&sdei_list_lock);
+
+ return sdei_unmask_local_cpu();
+}
+
/* When entering idle, mask/unmask events for this cpu */
static int sdei_pm_notifier(struct notifier_block *nb, unsigned long action,
void *data)
@@ -621,6 +800,7 @@ static int sdei_device_freeze(struct device *dev)
{
int err;

+ /* unregister private events */
cpuhp_remove_state(CPUHP_AP_ARM_SDEI_STARTING);

err = sdei_unregister_shared();