Re: [PATCH] Input: joystick: sidewinder - change msleep to usleep_range for small msecs

[Vojtech Pavlik <vojtech@ucw.cz>]

On Tue, Nov 29, 2016 at 01:08:22AM +0530, Aniroop Mathur wrote:
> 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(6) will make the process to
> sleep for a minimum period of 10 ms whereas usleep_range(6000, 6100) will make
> sure that the process does not sleep for more than 6100 us or 6.1ms

This patch seems clearly unnecessary. SW_TIMEOUT is 6ms or longer for
MS Sidewinder devices.

Vojtech

> Signed-off-by: Aniroop Mathur <a.mathur@samsung.com>
> ---
>  drivers/input/joystick/sidewinder.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/input/joystick/sidewinder.c b/drivers/input/joystick/sidewinder.c
> index 4a95b22..e5a1292 100644
> --- a/drivers/input/joystick/sidewinder.c
> +++ b/drivers/input/joystick/sidewinder.c
> @@ -50,7 +50,7 @@ MODULE_LICENSE("GPL");
>  
>  #define SW_START	600	/* The time we wait for the first bit [600 us] */
>  #define SW_STROBE	60	/* Max time per bit [60 us] */
> -#define SW_TIMEOUT	6	/* Wait for everything to settle [6 ms] */
> +#define SW_TIMEOUT	6000	/* Wait for everything to settle [6000 us] */
>  #define SW_KICK		45	/* Wait after A0 fall till kick [45 us] */
>  #define SW_END		8	/* Number of bits before end of packet to kick */
>  #define SW_FAIL		16	/* Number of packet read errors to fail and reinitialize */
> @@ -139,7 +139,7 @@ static int sw_read_packet(struct gameport *gameport, unsigned char *buf, int len
>  	unsigned char pending, u, v;
>  
>  	i = -id;						/* Don't care about data, only want ID */
> -	timeout = id ? gameport_time(gameport, SW_TIMEOUT * 1000) : 0; /* Set up global timeout for ID packet */
> +	timeout = id ? gameport_time(gameport, SW_TIMEOUT) : 0; /* Set up global timeout for ID packet */
>  	kick = id ? gameport_time(gameport, SW_KICK) : 0;	/* Set up kick timeout for ID packet */
>  	start = gameport_time(gameport, SW_START);
>  	strobe = gameport_time(gameport, SW_STROBE);
> @@ -248,7 +248,7 @@ static void sw_init_digital(struct gameport *gameport)
>  	i = 0;
>          do {
>                  gameport_trigger(gameport);			/* Trigger */
> -		t = gameport_time(gameport, SW_TIMEOUT * 1000);
> +		t = gameport_time(gameport, SW_TIMEOUT);
>  		while ((gameport_read(gameport) & 1) && t) t--;	/* Wait for axis to fall back to 0 */
>                  udelay(seq[i]);					/* Delay magic time */
>          } while (seq[++i]);
> @@ -483,13 +483,13 @@ static int sw_read(struct sw *sw)
>  		" - reinitializing joystick.\n", sw->gameport->phys);
>  
>  	if (!i && sw->type == SW_ID_3DP) {					/* 3D Pro can be in analog mode */
> -		mdelay(3 * SW_TIMEOUT);
> +		mdelay(3 * (SW_TIMEOUT / 1000));
>  		sw_init_digital(sw->gameport);
>  	}
>  
> -	mdelay(SW_TIMEOUT);
> +	mdelay(SW_TIMEOUT / 1000);
>  	i = sw_read_packet(sw->gameport, buf, SW_LENGTH, 0);			/* Read normal data packet */
> -	mdelay(SW_TIMEOUT);
> +	mdelay(SW_TIMEOUT / 1000);
>  	sw_read_packet(sw->gameport, buf, SW_LENGTH, i);			/* Read ID packet, this initializes the stick */
>  
>  	sw->fail = SW_FAIL;
> @@ -616,14 +616,14 @@ static int sw_connect(struct gameport *gameport, struct gameport_driver *drv)
>  		gameport->phys, gameport->io, gameport->speed);
>  
>  	i = sw_read_packet(gameport, buf, SW_LENGTH, 0);		/* Read normal packet */
> -	msleep(SW_TIMEOUT);
> +	usleep_range(SW_TIMEOUT, SW_TIMEOUT + 100);
>  	dbg("Init 1: Mode %d. Length %d.", m , i);
>  
>  	if (!i) {							/* No data. 3d Pro analog mode? */
>  		sw_init_digital(gameport);				/* Switch to digital */
> -		msleep(SW_TIMEOUT);
> +		usleep_range(SW_TIMEOUT, SW_TIMEOUT + 100);
>  		i = sw_read_packet(gameport, buf, SW_LENGTH, 0);	/* Retry reading packet */
> -		msleep(SW_TIMEOUT);
> +		usleep_range(SW_TIMEOUT, SW_TIMEOUT + 100);
>  		dbg("Init 1b: Length %d.", i);
>  		if (!i) {						/* No data -> FAIL */
>  			err = -ENODEV;
> @@ -636,7 +636,7 @@ static int sw_connect(struct gameport *gameport, struct gameport_driver *drv)
>  	dbg("Init 2: Mode %d. ID Length %d.", m, j);
>  
>  	if (j <= 0) {							/* Read ID failed. Happens in 1-bit mode on PP */
> -		msleep(SW_TIMEOUT);
> +		usleep_range(SW_TIMEOUT, SW_TIMEOUT + 100);
>  		i = sw_read_packet(gameport, buf, SW_LENGTH, 0);	/* Retry reading packet */
>  		m |= sw_guess_mode(buf, i);
>  		dbg("Init 2b: Mode %d. Length %d.", m, i);
> @@ -644,7 +644,7 @@ static int sw_connect(struct gameport *gameport, struct gameport_driver *drv)
>  			err = -ENODEV;
>  			goto fail2;
>  		}
> -		msleep(SW_TIMEOUT);
> +		usleep_range(SW_TIMEOUT, SW_TIMEOUT + 100);
>  		j = sw_read_packet(gameport, idbuf, SW_LENGTH, i);	/* Retry reading ID */
>  		dbg("Init 2c: ID Length %d.", j);
>  	}
> @@ -655,7 +655,7 @@ static int sw_connect(struct gameport *gameport, struct gameport_driver *drv)
>  
>  	do {
>  		k--;
> -		msleep(SW_TIMEOUT);
> +		usleep_range(SW_TIMEOUT, SW_TIMEOUT + 100);
>  		i = sw_read_packet(gameport, buf, SW_LENGTH, 0);	/* Read data packet */
>  		dbg("Init 3: Mode %d. Length %d. Last %d. Tries %d.", m, i, l, k);
>  
> -- 
> 2.6.2
> 

-- 
Vojtech Pavlik