Re: [PATCH V4 3/5] iio: adc: Add support for PMIC7 ADC

[Jishnu Prakash]

Hi Andy,

On 5/13/2020 3:18 PM, Andy Shevchenko wrote:
> On Wed, May 13, 2020 at 12:23 PM Jishnu Prakash <jprakash@xxxxxxxxxxxxxx> wrote:
> > The ADC architecture on PMIC7 is changed as compared to PMIC5. The
> > major change from PMIC5 is that all SW communication to ADC goes through
> > PMK8350, which communicates with other PMICs through PBS when the ADC
> > on PMK8350 works in master mode. The SID register is used to identify the
> > PMICs with which the PBS needs to communicate. Add support for the same.
> > +#define ADC7_CONV_TIMEOUT                      msecs_to_jiffies(10)
> ...
>
> > +       ret = adc5_read(adc, ADC5_USR_DIG_PARAM, buf, sizeof(buf));
> > +       if (ret < 0)
> Is ' < 0' part necessary?
> Ditto for same cases in other places in the code.
I'll fix this at all required locations in this patch in the next post.
> > +               return ret;
> ...
>
> > +       switch (mask) {
> > +       case IIO_CHAN_INFO_PROCESSED:
> > +               ret = adc7_do_conversion(adc, prop, chan,
> > +                                       &adc_code_volt, &adc_code_cur);
> > +               if (ret)
> > +                       return ret;
> > +
> > +               ret = qcom_adc5_hw_scale(prop->scale_fn_type,
> > +                       &adc5_prescale_ratios[prop->prescale],
> > +                       adc->data,
> > +                       adc_code_volt, val);
> > +
> > +               if (ret)
> > +                       return ret;
> > +
> > +               return IIO_VAL_INT;
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +
> > +       return 0;
> Dead code?
Right, I'll remove it in the next post.
> ...
>
> > +static int qcom_vadc7_scale_hw_calib_die_temp(
> > +                               const struct vadc_prescale_ratio *prescale,
> > +                               const struct adc5_data *data,
> > +                               u16 adc_code, int *result_mdec)
> > +{
> > +
> > +       int voltage, vtemp0, temp, i = ARRAY_SIZE(adcmap7_die_temp) - 1;
> How assignment to i is useful?


I'm using it in adcmap7_die_temp[i] below, to keep it within the 
character limit per line. I think it's more readable that way.

> > +       voltage = qcom_vadc_scale_code_voltage_factor(adc_code,
> > +                               prescale, data, 1);
> > +
> > +       if (adcmap7_die_temp[0].x > voltage) {
> > +               *result_mdec = DIE_TEMP_ADC7_SCALE_1;
> > +               return 0;
> > +       } else if (adcmap7_die_temp[i].x <= voltage) {
> Redundant 'else'.
The expression is different, it's adcmap7_die_temp[i] here, not 
adcmap7_die_temp[0].

> > +               *result_mdec = DIE_TEMP_ADC7_MAX;
> > +               return 0;
> > +       }
> > +
> > +       for (i = 0; i < ARRAY_SIZE(adcmap7_die_temp); i++)
> > +               if (adcmap7_die_temp[i].x > voltage)
> > +                       break;
> > +
> > +       vtemp0 = adcmap7_die_temp[i - 1].x;
> > +       voltage = voltage - vtemp0;
> > +       temp = div64_s64(voltage * DIE_TEMP_ADC7_SCALE_FACTOR,
> > +               adcmap7_die_temp[i - 1].y);
> > +       temp += DIE_TEMP_ADC7_SCALE_1 + (DIE_TEMP_ADC7_SCALE_2 * (i - 1));
> > +       *result_mdec = temp;
> > +
> > +       return 0;
> > +}
> ...
>
> > +#define RATIO_MAX_ADC7         0x4000
> Hmm... Why the last is in hex? Is it related to amount of bits in the
> hardware? Then probably better to use BIT().
It is the upper limit reading for a ratiometric calibration measurement, 
which is reported as a 14 bit reading. I'll change this in the next post.
>