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

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Date:   Fri, 22 May 2020 17:28:09 +0530
From:   Jishnu Prakash <jprakash@...eaurora.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     agross@...nel.org, Bjorn Andersson <bjorn.andersson@...aro.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        smohanad@...eaurora.org, kgunda@...eaurora.org,
        aghayal@...eaurora.org, Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-arm-msm@...r.kernel.org,
        linux-iio <linux-iio@...r.kernel.org>,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH V4 3/5] iio: adc: Add support for PMIC7 ADC

Hi Andy,

On 5/13/2020 3:18 PM, Andy Shevchenko wrote:
> On Wed, May 13, 2020 at 12:23 PM Jishnu Prakash <jprakash@...eaurora.org> 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.
>