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* [PATCH V2] media: smiapp: core: add small range to usleep_range
@ 2019-05-08 15:11 Nicholas Mc Guire
  0 siblings, 0 replies; only message in thread
From: Nicholas Mc Guire @ 2019-05-08 15:11 UTC (permalink / raw)
  To: Sakari Ailus
  Cc: Mauro Carvalho Chehab, linux-media, linux-kernel, Nicholas Mc Guire

No need for a high-accuracy delay here as long as it is more than 2
milliseconds this should be ok - as it is non-atomic context it will
be not be precise 2 milliseconds so giving the hrtimer subsystem 50
microseconds to merge timers and reduce interrupts.

Signed-off-by: Nicholas Mc Guire <hofrat@opentech.at>
---

Problem located by an experimental coccinelle script

V2: As Sakari Ailus <sakari.ailus@iki.fi> noted that the delays would be
    noticeable for the user but a range in the 50 microseconds range would
    be acceptable - the range is reduced from 2 millisecond to 50 microseconds
    which still gives the hrtimer subsystem some room for reducing interrupt
    load.

Patch was compile tested with: x86_64_defconfig + MEDIA_SUPPORT=m,
MEDIA_CAMERA_SUPPORT=y, MEDIA_CONTROLLER=y, VIDEO_V4L2_SUBDEV_API=y,
VIDEO_SMIAPP=m

Patch is against 5.1 (localversion-next is next-20190508)

 drivers/media/i2c/smiapp/smiapp-quirk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/i2c/smiapp/smiapp-quirk.c b/drivers/media/i2c/smiapp/smiapp-quirk.c
index 95c0272..59cb2a5 100644
--- a/drivers/media/i2c/smiapp/smiapp-quirk.c
+++ b/drivers/media/i2c/smiapp/smiapp-quirk.c
@@ -202,7 +202,7 @@ static int jt8ev1_post_streamoff(struct smiapp_sensor *sensor)
 		return rval;
 
 	/* Wait for 1 ms + one line => 2 ms is likely enough */
-	usleep_range(2000, 2000);
+	usleep_range(2000, 2050);
 
 	/* Restore it */
 	rval = smiapp_write_8(sensor, 0x3205, 0x00);
-- 
2.1.4


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