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Subject[PATCH 1/3] media: smiapp: core: add range to usleep_range
Date
Allow the hrtimer subsystem to coalesce delay timers of lower accuracy
by providing a suitable range

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

Problem located by an experimental coccinelle script

hrtimers in atomic context have limited accuracy due to possible
context-switching and interruption so the accuracy is limited
anyway. Giving the hrtimer subsystem a reasonable range for merging
hrtimers helps to reduce the load on the hrtimer subsystem. As this
delays do not seem to mandate high accuracy the range of a factor
two seems acceptable.

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
(with a number of sparse warnings on sizeof() usage)

Patch is against 5.1-rc3 (localversion-next is next-20190405)

drivers/media/i2c/smiapp/smiapp-core.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/smiapp/smiapp-core.c b/drivers/media/i2c/smiapp/smiapp-core.c
index 58a45c3..c0c29ec 100644
--- a/drivers/media/i2c/smiapp/smiapp-core.c
+++ b/drivers/media/i2c/smiapp/smiapp-core.c
@@ -1222,19 +1222,19 @@ static int smiapp_power_on(struct device *dev)
dev_err(&client->dev, "failed to enable vana regulator\n");
return rval;
}
- usleep_range(1000, 1000);
+ usleep_range(1000, 2000);

rval = clk_prepare_enable(sensor->ext_clk);
if (rval < 0) {
dev_dbg(&client->dev, "failed to enable xclk\n");
goto out_xclk_fail;
}
- usleep_range(1000, 1000);
+ usleep_range(1000, 2000);

gpiod_set_value(sensor->xshutdown, 1);

sleep = SMIAPP_RESET_DELAY(sensor->hwcfg->ext_clk);
- usleep_range(sleep, sleep);
+ usleep_range(sleep, sleep*2);

mutex_lock(&sensor->mutex);

@@ -1381,7 +1381,7 @@ static int smiapp_power_off(struct device *dev)

gpiod_set_value(sensor->xshutdown, 0);
clk_disable_unprepare(sensor->ext_clk);
- usleep_range(5000, 5000);
+ usleep_range(5000, 10000);
regulator_disable(sensor->vana);
sensor->streaming = false;

--
2.1.4
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