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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

drivers/s390/crypto/ap_bus.c

+53 −10
Original line number Diff line number Diff line
@@ -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);