Re: [PATCH] iio: cros_ec: Use default frequencies when EC returns invalid information

[Gwendal Grignou <gwendal@chromium.org>]

On Tue, Jun 30, 2020 at 8:12 AM Enric Balletbo i Serra
<enric.balletbo@collabora.com> wrote:
>
> Hi Gwendal,
>
> Thank you for the patch.
>
> On 30/6/20 9:59, Gwendal Grignou wrote:
> > Minimal and maximal frequencies supported by a sensor is queried.
> > On some older machines, these frequencies are not returned properly and
> > the EC returns 0 instead.
> > When returned maximal frequency is 0, ignore the information and use
> > default frequencies instead.
> >
> > Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
> > ---
> >  .../common/cros_ec_sensors/cros_ec_sensors_core.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> > index 36e3f20891f05..8437ff659260b 100644
> > --- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> > +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
> > @@ -289,7 +289,7 @@ int cros_ec_sensors_core_init(struct platform_device *pdev,
> >       struct cros_ec_sensorhub *sensor_hub = dev_get_drvdata(dev->parent);
> >       struct cros_ec_dev *ec = sensor_hub->ec;
> >       struct cros_ec_sensor_platform *sensor_platform = dev_get_platdata(dev);
> > -     u32 ver_mask;
> > +     u32 ver_mask, temp;
> >       int frequencies[ARRAY_SIZE(state->frequencies) / 2] = { 0 };
> >       int ret, i;
> >
> > @@ -345,8 +345,17 @@ int cros_ec_sensors_core_init(struct platform_device *pdev,
> >                                                &frequencies[2],
> >                                                &state->fifo_max_event_count);
> >               } else {
> > -                     frequencies[1] = state->resp->info_3.min_frequency;
> > -                     frequencies[2] = state->resp->info_3.max_frequency;
> > +                     if (state->resp->info_3.max_frequency == 0) {
>
> I might miss some use cases but I am wondering if this can be OR'ed with the
> above if, so there is only one call to get_default_min_max_freq
>
> > +                             get_default_min_max_freq(state->resp->info.type,
> > +                                                      &frequencies[1],
> > +                                                      &frequencies[2],
> > +                                                      &temp);
>
> and use &state->fifo_max_event_count instead of temp, so you don't need to
> create a new variable that is not used anymore. Or is in purpose?
It is on purpose: on some machines, min_frequency and max_frequency
are both 0, but fifo_max_event_count is correct and should be used.
>
> > +                     } else {
> > +                             frequencies[1] =
> > +                                     state->resp->info_3.min_frequency;
>
> nit: I think that you can take advantage of the new 100 character line length
> limit, here.
Fixed in the next patch.
>
> > +                             frequencies[2] =
> > +                                     state->resp->info_3.max_frequency;
>
> nit: ditto
>
> > +                     }
> >                       state->fifo_max_event_count =
> >                           state->resp->info_3.fifo_max_event_count;
> >               }
> >