[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: Felix Beck <felix.beck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

1 files changed, 53 insertions, 10 deletions

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index a1ab3e3efd1..62b6b55230d 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -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);