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Date: Tue, 29 Nov 2016 07:49:56 +0100
From: Vojtech Pavlik <vojtech@....cz>
To: Aniroop Mathur <a.mathur@...sung.com>
Cc: dmitry.torokhov@...il.com, linux-input@...r.kernel.org,
linux-kernel@...r.kernel.org, s.samuel@...sung.com,
r.mahale@...sung.com, aniroop.mathur@...il.com
Subject: Re: [PATCH] Input: joystick: sidewinder - change msleep to
usleep_range for small msecs
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@...sung.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
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