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SubjectRe: [PATCH] Input: joystick: gf2k - change msleep to usleep_range for small msecs
On Tue, Nov 29, 2016 at 01:11:49AM +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(4) will make the process to
> sleep for a minimum period of 10 ms whereas usleep_range(4000, 4100) will make
> sure that the process does not sleep for more than 4100 us or 4.1ms

And once more, patch not needed.

>
> Signed-off-by: Aniroop Mathur <a.mathur@samsung.com>
> ---
> drivers/input/joystick/gf2k.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/input/joystick/gf2k.c b/drivers/input/joystick/gf2k.c
> index 0f519db..e9d5095 100644
> --- a/drivers/input/joystick/gf2k.c
> +++ b/drivers/input/joystick/gf2k.c
> @@ -42,7 +42,7 @@ MODULE_LICENSE("GPL");
>
> #define GF2K_START 400 /* The time we wait for the first bit [400 us] */
> #define GF2K_STROBE 40 /* The time we wait for the first bit [40 us] */
> -#define GF2K_TIMEOUT 4 /* Wait for everything to settle [4 ms] */
> +#define GF2K_TIMEOUT 4000 /* Wait for everything to settle [4000 us] */
> #define GF2K_LENGTH 80 /* Max number of triplets in a packet */
>
> /*
> @@ -138,7 +138,7 @@ static void gf2k_trigger_seq(struct gameport *gameport, short *seq)
> i = 0;
> do {
> gameport_trigger(gameport);
> - t = gameport_time(gameport, GF2K_TIMEOUT * 1000);
> + t = gameport_time(gameport, GF2K_TIMEOUT);
> while ((gameport_read(gameport) & 1) && t) t--;
> udelay(seq[i]);
> } while (seq[++i]);
> @@ -259,11 +259,11 @@ static int gf2k_connect(struct gameport *gameport, struct gameport_driver *drv)
>
> gf2k_trigger_seq(gameport, gf2k_seq_reset);
>
> - msleep(GF2K_TIMEOUT);
> + usleep_range(GF2K_TIMEOUT, GF2K_TIMEOUT + 100);
>
> gf2k_trigger_seq(gameport, gf2k_seq_digital);
>
> - msleep(GF2K_TIMEOUT);
> + usleep_range(GF2K_TIMEOUT, GF2K_TIMEOUT + 100);
>
> if (gf2k_read_packet(gameport, GF2K_LENGTH, data) < 12) {
> err = -ENODEV;
> --
> 2.6.2
>

--
Vojtech Pavlik

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