Re: [PATCH 25/78] media: i2c: ccs-core: use pm_runtime_resume_and_get()

From: Mauro Carvalho Chehab
Date: Mon Apr 26 2021 - 10:02:01 EST


Em Sun, 25 Apr 2021 21:55:25 +0300
Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> escreveu:

> Hi Mauro,
>
> Thanks for the patch.
>
> On Sat, Apr 24, 2021 at 08:44:35AM +0200, Mauro Carvalho Chehab wrote:
> > 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.
> >
> > Use the new API, in order to cleanup the error check logic.
> >
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
> > ---
> > drivers/media/i2c/ccs/ccs-core.c | 11 +++++------
> > 1 file changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/media/i2c/ccs/ccs-core.c b/drivers/media/i2c/ccs/ccs-core.c
> > index 9dc3f45da3dc..1441ddcc9b35 100644
> > --- a/drivers/media/i2c/ccs/ccs-core.c
> > +++ b/drivers/media/i2c/ccs/ccs-core.c
> > @@ -1880,12 +1880,11 @@ static int ccs_pm_get_init(struct ccs_sensor *sensor)
> > struct i2c_client *client = v4l2_get_subdevdata(&sensor->src->sd);
> > int rval;
> >
> > - rval = pm_runtime_get_sync(&client->dev);
> > - if (rval < 0) {
> > - pm_runtime_put_noidle(&client->dev);
> > -
> > + rval = pm_runtime_resume_and_get(&client->dev);
> > + if (rval < 0)
> > return rval;
> > - } else if (!rval) {
> > +
> > + if (!rval) {
> > rval = v4l2_ctrl_handler_setup(&sensor->pixel_array->
> > ctrl_handler);
> > if (rval)
> > @@ -3089,7 +3088,7 @@ static int __maybe_unused ccs_suspend(struct device *dev)
> > bool streaming = sensor->streaming;
> > int rval;
> >
> > - rval = pm_runtime_get_sync(dev);
> > + rval = pm_runtime_resume_and_get(dev);
> > if (rval < 0) {
> > pm_runtime_put_noidle(dev);
>
> You'll need to drop pm_runtime_put_noidle() here.

OK!

---

On a non-related issue at the same code, after the change, the
suspend function will be:

static int __maybe_unused ccs_suspend(struct device *dev)
{
struct i2c_client *client = to_i2c_client(dev);
struct v4l2_subdev *subdev = i2c_get_clientdata(client);
struct ccs_sensor *sensor = to_ccs_sensor(subdev);
bool streaming = sensor->streaming;
int rval;

rval = pm_runtime_resume_and_get(dev);
if (rval < 0)
return -EAGAIN;

if (sensor->streaming)
ccs_stop_streaming(sensor);

/* save state for resume */
sensor->streaming = streaming;

return 0;
}

Not sure if "return -EAGAIN" is the right thing here. I mean,
the PM runtime core has two error conditions that are independent
on whatever the PM callback would be doing[1]:

if (dev->power.runtime_error)
retval = -EINVAL;
else if (dev->power.disable_depth > 0)
retval = -EACCES;

It would be very unlikely that trying to suspend again would solve
those conditions.

So, I guess that the right thing to do is to change the code
to do, instead:

static int __maybe_unused ccs_suspend(struct device *dev)
{
struct i2c_client *client = to_i2c_client(dev);
struct v4l2_subdev *subdev = i2c_get_clientdata(client);
struct ccs_sensor *sensor = to_ccs_sensor(subdev);
bool streaming = sensor->streaming;
int rval;

rval = pm_runtime_resume_and_get(dev);
if (rval < 0)
return rval;
...
}


[1] see rpm_resume() code at drivers/base/power/runtime.c.

Thanks,
Mauro