Input: joystick - use ktime for measuring timing

The current codes in gameport and analog joystick drivers for the time
accounting have a long-standing problem when the system is running
with CPU freq; since the timing is measured via TSC or sample counter,
the calculation isn't reliable.

In this patch, as a simple fix, use the standard ktime to measure the
timing.  In case where no high resolution timer is available,
use_ktime bool option is provided to both modules.  Setting
use_ktime=false switches to the old methods.

Tested-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

2 files changed, 92 insertions, 20 deletions

diff --git a/drivers/input/gameport/gameport.c b/drivers/input/gameport/gameport.c
index 24c41ba7d4e0..e29c04e2aff4 100644
--- a/drivers/input/gameport/gameport.c
+++ b/drivers/input/gameport/gameport.c
@@ -23,6 +23,7 @@
 #include <linux/workqueue.h>
 #include <linux/sched.h>        /* HZ */
 #include <linux/mutex.h>
+#include <linux/timekeeping.h>
 
 /*#include <asm/io.h>*/
 
@@ -30,6 +31,10 @@ MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
 MODULE_DESCRIPTION("Generic gameport layer");
 MODULE_LICENSE("GPL");
 
+static bool use_ktime = true;
+module_param(use_ktime, bool, 0400);
+MODULE_PARM_DESC(use_ktime, "Use ktime for measuring I/O speed");
+
 /*
  * gameport_mutex protects entire gameport subsystem and is taken
  * every time gameport port or driver registrered or unregistered.
@@ -76,6 +81,38 @@ static unsigned int get_time_pit(void)
 
 static int gameport_measure_speed(struct gameport *gameport)
 {
+        unsigned int i, t, tx;
+        u64 t1, t2, t3;
+        unsigned long flags;
+
+        if (gameport_open(gameport, NULL, GAMEPORT_MODE_RAW))
+                return 0;
+
+        tx = ~0;
+
+        for (i = 0; i < 50; i++) {
+                local_irq_save(flags);
+                t1 = ktime_get_ns();
+                for (t = 0; t < 50; t++)
+                        gameport_read(gameport);
+                t2 = ktime_get_ns();
+                t3 = ktime_get_ns();
+                local_irq_restore(flags);
+                udelay(i * 10);
+                t = (t2 - t1) - (t3 - t2);
+                if (t < tx)
+                        tx = t;
+        }
+
+        gameport_close(gameport);
+        t = 1000000 * 50;
+        if (tx)
+                t /= tx;
+        return t;
+}
+
+static int old_gameport_measure_speed(struct gameport *gameport)
+{
 #if defined(__i386__)
 
         unsigned int i, t, t1, t2, t3, tx;
@@ -521,7 +558,9 @@ static void gameport_add_port(struct gameport *gameport)
         if (gameport->parent)
                 gameport->parent->child = gameport;
 
-        gameport->speed = gameport_measure_speed(gameport);
+        gameport->speed = use_ktime ?
+                gameport_measure_speed(gameport) :
+                old_gameport_measure_speed(gameport);
 
         list_add_tail(&gameport->node, &gameport_list);
 
diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
index ab0fdcd36e18..4284080e481d 100644
--- a/drivers/input/joystick/analog.c
+++ b/drivers/input/joystick/analog.c
@@ -36,6 +36,7 @@
 #include <linux/gameport.h>
 #include <linux/jiffies.h>
 #include <linux/timex.h>
+#include <linux/timekeeping.h>
 
 #define DRIVER_DESC     "Analog joystick and gamepad driver"
 
@@ -43,6 +44,10 @@ MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
 MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_LICENSE("GPL");
 
+static bool use_ktime = true;
+module_param(use_ktime, bool, 0400);
+MODULE_PARM_DESC(use_ktime, "Use ktime for measuring I/O speed");
+
 /*
  * Option parsing.
  */
@@ -171,6 +176,25 @@ static unsigned long analog_faketime = 0;
 #warning Precise timer not defined for this architecture.
 #endif
 
+static inline u64 get_time(void)
+{
+        if (use_ktime) {
+                return ktime_get_ns();
+        } else {
+                unsigned int x;
+                GET_TIME(x);
+                return x;
+        }
+}
+
+static inline unsigned int delta(u64 x, u64 y)
+{
+        if (use_ktime)
+                return y - x;
+        else
+                return DELTA((unsigned int)x, (unsigned int)y);
+}
+
 /*
  * analog_decode() decodes analog joystick data and reports input events.
  */
@@ -226,7 +250,8 @@ static void analog_decode(struct analog *analog, int *axes, int *initial, int bu
 static int analog_cooked_read(struct analog_port *port)
 {
         struct gameport *gameport = port->gameport;
-        unsigned int time[4], start, loop, now, loopout, timeout;
+        u64 time[4], start, loop, now;
+        unsigned int loopout, timeout;
         unsigned char data[4], this, last;
         unsigned long flags;
         int i, j;
@@ -236,7 +261,7 @@ static int analog_cooked_read(struct analog_port *port)
 
         local_irq_save(flags);
         gameport_trigger(gameport);
-        GET_TIME(now);
+        now = get_time();
         local_irq_restore(flags);
 
         start = now;
@@ -249,16 +274,16 @@ static int analog_cooked_read(struct analog_port *port)
 
                 local_irq_disable();
                 this = gameport_read(gameport) & port->mask;
-                GET_TIME(now);
+                now = get_time();
                 local_irq_restore(flags);
 
-                if ((last ^ this) && (DELTA(loop, now) < loopout)) {
+                if ((last ^ this) && (delta(loop, now) < loopout)) {
                         data[i] = last ^ this;
                         time[i] = now;
                         i++;
                 }
 
-        } while (this && (i < 4) && (DELTA(start, now) < timeout));
+        } while (this && (i < 4) && (delta(start, now) < timeout));
 
         this <<= 4;
 
@@ -266,7 +291,7 @@ static int analog_cooked_read(struct analog_port *port)
                 this |= data[i];
                 for (j = 0; j < 4; j++)
                         if (data[i] & (1 << j))
-                                port->axes[j] = (DELTA(start, time[i]) << ANALOG_FUZZ_BITS) / port->loop;
+                                port->axes[j] = (delta(start, time[i]) << ANALOG_FUZZ_BITS) / port->loop;
         }
 
         return -(this != port->mask);
@@ -365,31 +390,39 @@ static void analog_close(struct input_dev *dev)
 static void analog_calibrate_timer(struct analog_port *port)
 {
         struct gameport *gameport = port->gameport;
-        unsigned int i, t, tx, t1, t2, t3;
+        unsigned int i, t, tx;
+        u64 t1, t2, t3;
         unsigned long flags;
 
-        local_irq_save(flags);
-        GET_TIME(t1);
+        if (use_ktime) {
+                port->speed = 1000000;
+        } else {
+                local_irq_save(flags);
+                t1 = get_time();
 #ifdef FAKE_TIME
-        analog_faketime += 830;
+                analog_faketime += 830;
 #endif
-        mdelay(1);
-        GET_TIME(t2);
-        GET_TIME(t3);
-        local_irq_restore(flags);
+                mdelay(1);
+                t2 = get_time();
+                t3 = get_time();
+                local_irq_restore(flags);
 
-        port->speed = DELTA(t1, t2) - DELTA(t2, t3);
+                port->speed = delta(t1, t2) - delta(t2, t3);
+        }
 
         tx = ~0;
 
         for (i = 0; i < 50; i++) {
                 local_irq_save(flags);
-                GET_TIME(t1);
-                for (t = 0; t < 50; t++) { gameport_read(gameport); GET_TIME(t2); }
-                GET_TIME(t3);
+                t1 = get_time();
+                for (t = 0; t < 50; t++) {
+                        gameport_read(gameport);
+                        t2 = get_time();
+                }
+                t3 = get_time();
                 local_irq_restore(flags);
                 udelay(i);
-                t = DELTA(t1, t2) - DELTA(t2, t3);
+                t = delta(t1, t2) - delta(t2, t3);
                 if (t < tx) tx = t;
         }