Commit fe137230 authored by Felix Beck's avatar Felix Beck Committed by Heiko Carstens
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[S390] ap: Use high-resolution timer for polling



The ap poll mechanism is converted to use a high-resolution timer for
polling. This allows more specific polling. With this a new sysfs
attribute is introduced to specify the polling rate in nanoseconds.
Signed-off-by: default avatarFelix Beck <felix.beck@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent ad211790
......@@ -34,13 +34,15 @@
#include <linux/mutex.h>
#include <asm/s390_rdev.h>
#include <asm/reset.h>
#include <linux/hrtimer.h>
#include <linux/ktime.h>
#include "ap_bus.h"
/* Some prototypes. */
static void ap_scan_bus(struct work_struct *);
static void ap_poll_all(unsigned long);
static void ap_poll_timeout(unsigned long);
static enum hrtimer_restart ap_poll_timeout(struct hrtimer *);
static int ap_poll_thread_start(void);
static void ap_poll_thread_stop(void);
static void ap_request_timeout(unsigned long);
......@@ -80,12 +82,15 @@ static DECLARE_WORK(ap_config_work, ap_scan_bus);
/*
* Tasklet & timer for AP request polling.
*/
static struct timer_list ap_poll_timer = TIMER_INITIALIZER(ap_poll_timeout,0,0);
static DECLARE_TASKLET(ap_tasklet, ap_poll_all, 0);
static atomic_t ap_poll_requests = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(ap_poll_wait);
static struct task_struct *ap_poll_kthread = NULL;
static DEFINE_MUTEX(ap_poll_thread_mutex);
static struct hrtimer ap_poll_timer;
/* In LPAR poll with 4kHz frequency. Poll every 250000 nanoseconds.
* If z/VM change to 1500000 nanoseconds to adjust to z/VM polling.*/
static unsigned long long poll_timeout = 250000;
/**
* ap_intructions_available() - Test if AP instructions are available.
......@@ -636,11 +641,39 @@ static ssize_t ap_poll_thread_store(struct bus_type *bus,
static BUS_ATTR(poll_thread, 0644, ap_poll_thread_show, ap_poll_thread_store);
static ssize_t poll_timeout_show(struct bus_type *bus, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%llu\n", poll_timeout);
}
static ssize_t poll_timeout_store(struct bus_type *bus, const char *buf,
size_t count)
{
unsigned long long time;
ktime_t hr_time;
/* 120 seconds = maximum poll interval */
if (sscanf(buf, "%llu\n", &time) != 1 || time < 1 || time > 120000000000)
return -EINVAL;
poll_timeout = time;
hr_time = ktime_set(0, poll_timeout);
if (!hrtimer_is_queued(&ap_poll_timer) ||
!hrtimer_forward(&ap_poll_timer, ap_poll_timer.expires, hr_time)) {
ap_poll_timer.expires = hr_time;
hrtimer_start(&ap_poll_timer, hr_time, HRTIMER_MODE_ABS);
}
return count;
}
static BUS_ATTR(poll_timeout, 0644, poll_timeout_show, poll_timeout_store);
static struct bus_attribute *const ap_bus_attrs[] = {
&bus_attr_ap_domain,
&bus_attr_config_time,
&bus_attr_poll_thread,
NULL
&bus_attr_poll_timeout,
NULL,
};
/**
......@@ -895,9 +928,10 @@ ap_config_timeout(unsigned long ptr)
*/
static inline void ap_schedule_poll_timer(void)
{
if (timer_pending(&ap_poll_timer))
if (hrtimer_is_queued(&ap_poll_timer))
return;
mod_timer(&ap_poll_timer, jiffies + AP_POLL_TIME);
hrtimer_start(&ap_poll_timer, ktime_set(0, poll_timeout),
HRTIMER_MODE_ABS);
}
/**
......@@ -1115,13 +1149,14 @@ EXPORT_SYMBOL(ap_cancel_message);
/**
* ap_poll_timeout(): AP receive polling for finished AP requests.
* @unused: Unused variable.
* @unused: Unused pointer.
*
* Schedules the AP tasklet.
* Schedules the AP tasklet using a high resolution timer.
*/
static void ap_poll_timeout(unsigned long unused)
static enum hrtimer_restart ap_poll_timeout(struct hrtimer *unused)
{
tasklet_schedule(&ap_tasklet);
return HRTIMER_NORESTART;
}
/**
......@@ -1344,6 +1379,14 @@ int __init ap_module_init(void)
ap_config_timer.expires = jiffies + ap_config_time * HZ;
add_timer(&ap_config_timer);
/* Setup the high resultion poll timer.
* If we are running under z/VM adjust polling to z/VM polling rate.
*/
if (MACHINE_IS_VM)
poll_timeout = 1500000;
hrtimer_init(&ap_poll_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
ap_poll_timer.function = ap_poll_timeout;
/* Start the low priority AP bus poll thread. */
if (ap_thread_flag) {
rc = ap_poll_thread_start();
......@@ -1355,7 +1398,7 @@ int __init ap_module_init(void)
out_work:
del_timer_sync(&ap_config_timer);
del_timer_sync(&ap_poll_timer);
hrtimer_cancel(&ap_poll_timer);
destroy_workqueue(ap_work_queue);
out_root:
s390_root_dev_unregister(ap_root_device);
......@@ -1386,7 +1429,7 @@ void ap_module_exit(void)
ap_reset_domain();
ap_poll_thread_stop();
del_timer_sync(&ap_config_timer);
del_timer_sync(&ap_poll_timer);
hrtimer_cancel(&ap_poll_timer);
destroy_workqueue(ap_work_queue);
tasklet_kill(&ap_tasklet);
s390_root_dev_unregister(ap_root_device);
......
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