Commit 76460a7b authored by Takashi Iwai's avatar Takashi Iwai Committed by Dmitry Torokhov
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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: default avatarClemens Ladisch <clemens@ladisch.de>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
parent a3b3ca75

drivers/input/gameport/gameport.c

+40 −1
Original line number Diff line number Diff line
@@ -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.
@@ -75,6 +80,38 @@ 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__)
@@ -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);

drivers/input/joystick/analog.c

+52 −19
Original line number Diff line number Diff line
@@ -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;



	if (use_ktime) {

		port->speed = 1000000;

	} else {

		local_irq_save(flags);

	GET_TIME(t1);

		t1 = get_time();

#ifdef FAKE_TIME

		analog_faketime += 830;

#endif

		mdelay(1);

	GET_TIME(t2);

	GET_TIME(t3);

		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;

	}

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