[PATCH 1/3] media: smiapp: core: add range to usleep_range

[PATCH 1/3] media: smiapp: core: add range to usleep_range

[Nicholas Mc Guire]

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

[PATCH 2/3] media: smiapp: regs: add range to usleep_range

[Nicholas Mc Guire]

As this is a retry loop for a sender not responding there is no reason
to mandate a high accuracy delay - extend the sleep range to 2-4ms
so that the hrtimer subsystem can work efficiently.

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

Problem located by an experimental coccinelle script

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-rc3 (localversion-next is next-20190405)

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

diff --git a/drivers/media/i2c/smiapp/smiapp-regs.c b/drivers/media/i2c/smiapp/smiapp-regs.c
index 145653d..dfa4f99 100644
--- a/drivers/media/i2c/smiapp/smiapp-regs.c
+++ b/drivers/media/i2c/smiapp/smiapp-regs.c
@@ -276,7 +276,7 @@ int smiapp_write_no_quirk(struct smiapp_sensor *sensor, u32 reg, u32 val)
 			return 0;
 		}
 
-		usleep_range(2000, 2000);
+		usleep_range(2000, 4000);
 	}
 
 	dev_err(&client->dev,
-- 
2.1.4

[PATCH 3/3] media: smiapp: quirk: add range to usleep_range

[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 2+ anyway and streamoff delays in the millisecond range should not
hurt.

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

Problem located by an experimental coccinelle script

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-rc3 (localversion-next is next-20190405)

 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..21b7fdc 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, 4000);
 
 	/* Restore it */
 	rval = smiapp_write_8(sensor, 0x3205, 0x00);
-- 
2.1.4

Re: [PATCH 1/3] media: smiapp: core: add range to usleep_range

[Sakari Ailus]

Hi Nicholas,

On Sun, Apr 07, 2019 at 04:16:02AM +0200, Nicholas Mc Guire wrote:
> 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)

The delays are exact for the reason that they are user-visible delays in
image capturing related use cases. Sometimes milliseconds matter, or at
least adding more does not help.

> 
>  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;
>  

-- 
Sakari Ailus

Re: [PATCH 1/3] media: smiapp: core: add range to usleep_range

[Nicholas Mc Guire]

On Tue, Apr 30, 2019 at 04:49:44PM +0300, Sakari Ailus wrote:
> Hi Nicholas,
> 
> On Sun, Apr 07, 2019 at 04:16:02AM +0200, Nicholas Mc Guire wrote:
> > 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)
> 
> The delays are exact for the reason that they are user-visible delays in
> image capturing related use cases. Sometimes milliseconds matter, or at
> least adding more does not help.
>

Actually it can be better iwith respect to jitter to let the hrtimer 
subsystem use an existing timer event than to have a close by second event 
and the accuracy is determined by the non-atomic context anyway - 
so while the proposed delay extension might be excessive in your case
I would still suggest to try to get away from a range of 0 - even if
you only end up with (1000,1050) that would be an advantage for the
timer subsystem.

thx!
hofrat
 
> > 
> >  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;
> >  
> 
> -- 
> Sakari Ailus

Re: [PATCH 1/3] media: smiapp: core: add range to usleep_range

[Sakari Ailus]

On Sat, May 04, 2019 at 11:46:35AM +0200, Nicholas Mc Guire wrote:
> On Tue, Apr 30, 2019 at 04:49:44PM +0300, Sakari Ailus wrote:
> > Hi Nicholas,
> > 
> > On Sun, Apr 07, 2019 at 04:16:02AM +0200, Nicholas Mc Guire wrote:
> > > 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)
> > 
> > The delays are exact for the reason that they are user-visible delays in
> > image capturing related use cases. Sometimes milliseconds matter, or at
> > least adding more does not help.
> >
> 
> Actually it can be better iwith respect to jitter to let the hrtimer 
> subsystem use an existing timer event than to have a close by second event 
> and the accuracy is determined by the non-atomic context anyway - 
> so while the proposed delay extension might be excessive in your case
> I would still suggest to try to get away from a range of 0 - even if
> you only end up with (1000,1050) that would be an advantage for the
> timer subsystem.

Sounds reasonable to me. Would you like to send v2?

Thanks.

-- 
Sakari Ailus