Em Wed, 5 May 2021 12:10:40 +0100
Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> escreveu:
> On Wed, 5 May 2021 11:41:56 +0200
> Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx> wrote:
>
> > The PM runtime get logic is currently broken, as it checks if
> > ret is zero instead of checking if it is an error code,
> > as reported by Dan Carpenter.
> >
> > While here, use the pm_runtime_resume_and_get() as added by:
> > commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> > added pm_runtime_resume_and_get() in order to automatically handle
> > dev->power.usage_count decrement on errors. As a bonus, such function
> > always return zero on success.
> >
> > It should also be noticed that a fail of pm_runtime_get_sync() would
> > potentially result in a spurious runtime_suspend(), instead of
> > using pm_runtime_put_noidle().
>
> Irony here is that pm_runtime_resume_and_get() returns <= 0 so with that
> function change, you can stick with if (ret) and still be correct.
>
> So only one of the two changes is needed to fix the bug.
Yeah, I noticed ;-)
On media, almost all devices have I2C bus(es), and I2C send/receive functions
return positive values. So, a good practice is to check for errors with:
if (ret < 0)
That's why I opted to keep both changes here ;-)
Regards,
Mauro
>
> J
> >
> > Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > Reviewed-by: Daniele Alessandrelli <daniele.alessandrelli@xxxxxxxxx>
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
> > ---
> > drivers/media/i2c/imx334.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/i2c/imx334.c b/drivers/media/i2c/imx334.c
> > index 047aa7658d21..23f28606e570 100644
> > --- a/drivers/media/i2c/imx334.c
> > +++ b/drivers/media/i2c/imx334.c
> > @@ -717,9 +717,9 @@ static int imx334_set_stream(struct v4l2_subdev *sd, int enable)
> > }
> >
> > if (enable) {
> > - ret = pm_runtime_get_sync(imx334->dev);
> > - if (ret)
> > - goto error_power_off;
> > + ret = pm_runtime_resume_and_get(imx334->dev);
> > + if (ret < 0)
> > + goto error_unlock;
> >
> > ret = imx334_start_streaming(imx334);
> > if (ret)
> > @@ -737,6 +737,7 @@ static int imx334_set_stream(struct v4l2_subdev *sd, int enable)
> >
> > error_power_off:
> > pm_runtime_put(imx334->dev);
> > +error_unlock:
> > mutex_unlock(&imx334->mutex);
> >
> > return ret;
>
Thanks,
Mauro
