linux-kernel - [PATCH] Input: joystick: analog - change msleep to usleep

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Date:   Tue, 29 Nov 2016 01:11:31 +0530
From:   Aniroop Mathur <a.mathur@...sung.com>
To:     vojtech@....cz, dmitry.torokhov@...il.com,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     s.samuel@...sung.com, r.mahale@...sung.com,
        aniroop.mathur@...il.com, Aniroop Mathur <a.mathur@...sung.com>
Subject: [PATCH] Input: joystick: analog - change msleep to usleep_range for small msecs

msleep(1~20) may not do what the caller intends, and will often sleep longer.
(~20 ms actual sleep for any value given in the 1~20ms range)
This is not the desired behaviour for many cases like device resume time,
device suspend time, device enable time, connection time, probe time,
loops, retry logic, etc
msleep is built on jiffies / legacy timers which are not precise whereas
usleep_range is build on top of hrtimers so the wakeups are precise.
Thus, change msleep to usleep_range for precise wakeups.

For example:
On a machine with tick rate / HZ as 100, msleep(3) will make the process to
sleep for a minimum period of 10 ms whereas usleep_range(3000, 3100) will make
sure that the process does not sleep for more than 3100 us or 3.1ms

Signed-off-by: Aniroop Mathur <a.mathur@...sung.com>
---
 drivers/input/joystick/analog.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
index 3d8ff09..2891704 100644
--- a/drivers/input/joystick/analog.c
+++ b/drivers/input/joystick/analog.c
@@ -88,7 +88,7 @@ MODULE_PARM_DESC(map, "Describes analog joysticks type/capabilities");
 #define ANALOG_EXTENSIONS	0x7ff00
 #define ANALOG_GAMEPAD		0x80000
 
-#define ANALOG_MAX_TIME		3	/* 3 ms */
+#define ANALOG_MAX_TIME		3000	/* 3000 us */
 #define ANALOG_LOOP_TIME	2000	/* 2 * loop */
 #define ANALOG_SAITEK_DELAY	200	/* 200 us */
 #define ANALOG_SAITEK_TIME	2000	/* 2000 us */
@@ -257,7 +257,7 @@ static int analog_cooked_read(struct analog_port *port)
 	int i, j;
 
 	loopout = (ANALOG_LOOP_TIME * port->loop) / 1000;
-	timeout = ANALOG_MAX_TIME * port->speed;
+	timeout = (ANALOG_MAX_TIME / 1000) * port->speed;
 
 	local_irq_save(flags);
 	gameport_trigger(gameport);
@@ -625,20 +625,20 @@ static int analog_init_port(struct gameport *gameport, struct gameport_driver *d
 
 		gameport_trigger(gameport);
 		t = gameport_read(gameport);
-		msleep(ANALOG_MAX_TIME);
+		usleep_range(ANALOG_MAX_TIME, ANALOG_MAX_TIME + 100);
 		port->mask = (gameport_read(gameport) ^ t) & t & 0xf;
 		port->fuzz = (port->speed * ANALOG_FUZZ_MAGIC) / port->loop / 1000 + ANALOG_FUZZ_BITS;
 
 		for (i = 0; i < ANALOG_INIT_RETRIES; i++) {
 			if (!analog_cooked_read(port))
 				break;
-			msleep(ANALOG_MAX_TIME);
+			usleep_range(ANALOG_MAX_TIME, ANALOG_MAX_TIME + 100);
 		}
 
 		u = v = 0;
 
-		msleep(ANALOG_MAX_TIME);
-		t = gameport_time(gameport, ANALOG_MAX_TIME * 1000);
+		usleep_range(ANALOG_MAX_TIME, ANALOG_MAX_TIME + 100);
+		t = gameport_time(gameport, ANALOG_MAX_TIME);
 		gameport_trigger(gameport);
 		while ((gameport_read(port->gameport) & port->mask) && (u < t))
 			u++;
-- 
2.6.2