Hi Florian,
On Tue, May 07, 2019 at 10:44:00AM -0700, Florian Fainelli wrote:
> On 5/7/19 6:55 AM, Guenter Roeck wrote:
> > Hi Florian,
> >
> > On 5/6/19 3:41 PM, Florian Fainelli wrote:
> >> If the SCMI firmware implementation is reporting values in a scale that
> >> is different from the HWMON units, we need to scale up or down the value
> >> according to how far appart they are.
> >>
> >> Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> >> ---
> >> drivers/hwmon/scmi-hwmon.c | 55 +++++++++++++++++++++++++++++++-------
> >> 1 file changed, 46 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/drivers/hwmon/scmi-hwmon.c b/drivers/hwmon/scmi-hwmon.c
> >> index a80183a488c5..e9913509cb88 100644
> >> --- a/drivers/hwmon/scmi-hwmon.c
> >> +++ b/drivers/hwmon/scmi-hwmon.c
> >> @@ -18,6 +18,51 @@ struct scmi_sensors {
> >> const struct scmi_sensor_info **info[hwmon_max];
> >> };
> >> +static enum hwmon_sensor_types scmi_types[] = {
> >> + [TEMPERATURE_C] = hwmon_temp,
> >> + [VOLTAGE] = hwmon_in,
> >> + [CURRENT] = hwmon_curr,
> >> + [POWER] = hwmon_power,
> >> + [ENERGY] = hwmon_energy,
> >> +};
> >> +
> >> +static u64 scmi_hwmon_scale(const struct scmi_sensor_info *sensor,
> >> u64 value)
> >> +{
> >> + u64 scaled_value = value;
> >
> > I don't think that variable is necessary.
> >
> >> + s8 desired_scale;
> >
> > Just scale ? Also, you could assign scale here directly, and subtract
> > the offset below. Then "n" would not be necessary.
> > Such as
> > s8 scale = sensor->scale; // assuming scale is s8
> > ...
> > case CURRENT:
> > scale += 3;
> > ...
> >
> > That would also be less confusing, since it would avoid the double
> > negation.
> >
> >> + int n, p;
> >
> >> +
> >> + switch (sensor->type) {
> >> + case TEMPERATURE_C:
> >> + case VOLTAGE:
> >> + case CURRENT:
> >> + /* fall through */
> > Unnecessary comment
>
> Is not removing the comment going to upset gcc when using
> -Wimplicit-fallthrough?
>
There is no implicit fallthrough, and the comment would have to be
ahead of the previous case statement. Such as:
case VOLTAGE:
scale++;
/* fall through */
case CURRENT:
scale++;
break;
...
Two case statements together don't count as fall through.
Guenter
> >
> >> + desired_scale = -3;
> >> + break;
> >> + case POWER:
> >> + case ENERGY:
> >> + /* fall through */
> > Unnecessary comment.
> >
> >> + desired_scale = -6;
> >> + break;
> >> + default:
> >> + return scaled_value;
> >
> > Here we presumably want a scale of 0. However, if the scale passed
> > from SCMI is, say, -5 or +5, we return the original (unadjusted)
> > value. Seems to me we would still want to adjust the value to match
> > hwmon expectations. Am I missing something ?
>
> You raise a valid point, not that could happen today because if the
> sensor type has a value we don't recognize, we have not registered it,
> so we would not even try to read rom it, but let's be future proof.
>
> >
> >> + }
> >> +
> >> + n = (s8)sensor->scale - desired_scale;
> >> + if (n == 0)
> >
> > Indentation seems off here.
> >
> >> + return scaled_value;
> >> +
> >> + for (p = 0; p < abs(n); p++) {
> >> + /* Need to scale up from sensor to HWMON */
> >> + if (n > 0)
> >> + scaled_value *= 10;
> >> + else
> >> + do_div(scaled_value, 10);
> >> + }
> >
> > Something like
> >
> > factor = pow10(abs(scale));
> > if (scale > 0)
> > value *= factor;
> > else
> > do_div(value, factor);
> >
> > would avoid the repeated abs() and do_div(). Unfortunately there is
> > no pow10() helper, so you would have to write that. Still, I think
> > that would be much more efficient.
>
> Sounds reasonable. Thanks for your feedback!
> --
> Florian
