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Date:   Sat, 7 Jan 2017 14:23:22 -0500
From:   Jonathan Cameron <jic23@...nel.org>
To:     Chen-Yu Tsai <wens@...e.org>,
        Quentin Schulz <quentin.schulz@...e-electrons.com>
Cc:     knaack.h@....de, Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sebastian Reichel <sre@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Lee Jones <lee.jones@...aro.org>, linux-iio@...r.kernel.org,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Icenowy Zheng <icenowy@...c.xyz>,
        Bruno Prémont <bonbons@...ux-vserver.org>
Subject: Re: [PATCH 03/22] iio: adc: add support for X-Powers AXP20X and
 AXP22X PMICs ADCs

On 05/01/17 05:28, Chen-Yu Tsai wrote:
> On Thu, Jan 5, 2017 at 5:50 PM, Quentin Schulz
> <quentin.schulz@...e-electrons.com> wrote:
>> On 05/01/2017 09:27, Chen-Yu Tsai wrote:
>>> On Thu, Jan 5, 2017 at 4:06 PM, Quentin Schulz
>>> <quentin.schulz@...e-electrons.com> wrote:
>>>> Hi Chen-Yu,
>>>>
>>>> On 05/01/2017 06:42, Chen-Yu Tsai wrote:
>>>>> On Tue, Jan 3, 2017 at 12:37 AM, Quentin Schulz
>>>>> <quentin.schulz@...e-electrons.com> wrote:
>>>> [...]
>>>>>> +
>>>>>> +#define AXP20X_ADC_RATE_MASK                   (3 << 6)
>>>>>> +#define AXP20X_ADC_RATE_25HZ                   (0 << 6)
>>>>>> +#define AXP20X_ADC_RATE_50HZ                   BIT(6)
>>>>>
>>>>> Please be consistent with the format.
>>>>>
>>>>>> +#define AXP20X_ADC_RATE_100HZ                  (2 << 6)
>>>>>> +#define AXP20X_ADC_RATE_200HZ                  (3 << 6)
>>>>>> +
>>>>>> +#define AXP22X_ADC_RATE_100HZ                  (0 << 6)
>>>>>> +#define AXP22X_ADC_RATE_200HZ                  BIT(6)
>>>>>> +#define AXP22X_ADC_RATE_400HZ                  (2 << 6)
>>>>>> +#define AXP22X_ADC_RATE_800HZ                  (3 << 6)
>>>>>
>>>>> These are power-of-2 multiples of some base rate. May I suggest
>>>>> a formula macro instead. Either way, you seem to be using only
>>>>> one value. Will this be made configurable in the future?
>>>>>
>>>>
>>>> Yes, I could use a formula macro instead. No plan to make it
>>>> configurable, should I make it configurable?
>>>
>>> I don't see a use case for that atm.
>>>
>>>>>> +
>>>>>> +#define AXP20X_ADC_CHANNEL(_channel, _name, _type, _reg)       \
>>>>>> +       {                                                       \
>>>>>> +               .type = _type,                                  \
>>>>>> +               .indexed = 1,                                   \
>>>>>> +               .channel = _channel,                            \
>>>>>> +               .address = _reg,                                \
>>>>>> +               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |  \
>>>>>> +                                     BIT(IIO_CHAN_INFO_SCALE), \
>>>>>> +               .datasheet_name = _name,                        \
>>>>>> +       }
>>>>>> +
>>>>>> +#define AXP20X_ADC_CHANNEL_OFFSET(_channel, _name, _type, _reg) \
>>>>>> +       {                                                       \
>>>>>> +               .type = _type,                                  \
>>>>>> +               .indexed = 1,                                   \
>>>>>> +               .channel = _channel,                            \
>>>>>> +               .address = _reg,                                \
>>>>>> +               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |  \
>>>>>> +                                     BIT(IIO_CHAN_INFO_SCALE) |\
>>>>>> +                                     BIT(IIO_CHAN_INFO_OFFSET),\
>>>>>> +               .datasheet_name = _name,                        \
>>>>>> +       }
>>>>>> +
>>>>>> +struct axp20x_adc_iio {
>>>>>> +       struct iio_dev          *indio_dev;
>>>>>> +       struct regmap           *regmap;
>>>>>> +};
>>>>>> +
>>>>>> +enum axp20x_adc_channel {
>>>>>> +       AXP20X_ACIN_V = 0,
>>>>>> +       AXP20X_ACIN_I,
>>>>>> +       AXP20X_VBUS_V,
>>>>>> +       AXP20X_VBUS_I,
>>>>>> +       AXP20X_TEMP_ADC,
>>>>>
>>>>> PMIC_TEMP would be better. And please save a slot for TS input.
>>>>>
>>>>
>>>> ACK.
>>>>
>>>> Hum.. I'm wondering what should be the IIO type of the TS input channel
>>>> then? The TS Pin can be used in two modes: either to monitor the
>>>> temperature of the battery or as an external ADC, at least that's what I
>>>> understand from the datasheet.
>>>
>>> AFAIK the battery charge/discharge high/low temperature threshold
>>> registers take values in terms of voltage, not actual temperature.
>>> And the temperature readout kind of depends on the thermoresistor
>>> one is using. So I think "voltage" would be the proper type.
>>>
>>
>> ACK. Should I just add TS_IN in axp20x_adc_channel enum but not add it
>> in the exposed IIO channels ("saving" the slot but not using it)?
> 
> Sure. Or you could skip the number with
> 
>     AXP20X_GPIO0_V = 6,
> 
>>>>
>>>>>> +       AXP20X_GPIO0_V,
>>>>>> +       AXP20X_GPIO1_V,
>>>>>
>>>>> Please skip a slot for "battery instantaneous power".
>>>>>
>>>>>> +       AXP20X_BATT_V,
>>>>>> +       AXP20X_BATT_CHRG_I,
>>>>>> +       AXP20X_BATT_DISCHRG_I,
>>>>>> +       AXP20X_IPSOUT_V,
>>>>>> +};
>>>>>> +
>>>>>> +enum axp22x_adc_channel {
>>>>>> +       AXP22X_TEMP_ADC = 0,
>>>>>
>>>>> Same comments as AXP20X_TEMP_ADC.
>>>>>
>>>>>> +       AXP22X_BATT_V,
>>>>>> +       AXP22X_BATT_CHRG_I,
>>>>>> +       AXP22X_BATT_DISCHRG_I,
>>>>>> +};
>>>>>
>>>>> Shouldn't these channel numbers be exported as part of the device tree
>>>>> bindings? At the very least, they shouldn't be changed.
>>>>>
>>>>
>>>> I don't understand what you mean by that. Do you mean you want a
>>>> consistent numbering between the AXP20X and the AXP22X, so that
>>>> AXP22X_BATT_V would have the same channel number than AXP20X_BATT_V?
>>>>
>>>> Could you explain a bit more your thoughts on the channel numbers being
>>>> exported as part of the device tree bindings?
>>>
>>> What I meant was that, since you are referencing the channels in the
>>> device tree, the numbering scheme would be part of the device tree
>>> binding, and should never be changed. So either these would be macros
>>> in include/dt-bindings/, or a big warning should be put before it.
>>>
>>
>> ACK.
>>
>>> But see my reply on patch 7, about do we actually need to expose this
>>> in the device tree.
>>>
>>
>> I don't know what's the best.
> 
> Then let's not expose it in the device tree for now. It's easier to
> add it later than to remove it.
> 
>>
>>>>> Also please add a comment saying that the channels are numbered
>>>>> in the order of their respective registers, and not the table
>>>>> describing the ADCs in the datasheet (9.7 Signal Capture for AXP209
>>>>> and 9.5 E-Gauge for AXP221).
>>>>>
>>>>
>>>> Yes I can.
>>>>
>>>> What about Rob wanting channel numbers to start at zero for each
>>>> different IIO type (i.e., today we have AXP22X_BATT_CHRG_I being
>>>> exported as in_current1_raw whereas he wants in_current0_raw).
>>>
>>> Hmm... I missed this. Are you talking about IIO or hwmon? IIRC
>>> hwmon numbers things starting at 1.
>>>
>>
>> About IIO.
>>
>> Today, we have exposed:
>> in_voltage0_raw for acin_v
>> in_current1_raw for acin_i
>> in_voltage2_raw for vbus_v
>> in_current3_raw for vbus_i
>> in_temp4_raw for adc_temp
>> in_voltage5_raw for gpio0_v
>> in_voltage6_raw for gpio1_v
>> in_voltage7_raw for batt_v
>> in_current8_raw for batt_chrg_i
>> in_current9_raw for batt_dischrg_i
>> in_voltage10_raw for ipsout_v
>>
>> but I think what Rob wants is:
>>
>> in_voltage0_raw acin_v
>> in_current0_raw for acin_i
>> in_voltage1_raw for vbus_v
>> in_current1_raw for vbus_i
>> in_temp_raw for adc_temp
>> in_voltage2_raw for gpio0_v
>> in_voltage3_raw for gpio1_v
>> in_voltage4_raw for batt_v
>> in_current2_raw for batt_chrg_i
>> in_current3_raw for batt_dischrg_i
>> in_voltage5_raw for ipsout_v
> 
> I think that's doable. If I understand IIO code correctly, the channel
> number is not used anywhere in the core code for dereferencing. It's
> used for sysfs entries (when .indexed is set) and events. However
> the twl4030 and twl6030 drivers use our current exposed scheme.
> I suppose its best to get some input from the IIO maintainer.
If we are doing it to superficially group channels that are measuring
different things about the same physical system then I'm fine with
mappings with holes in them.

It's not actually specified anywhere that we can't allow this and
IIRC there are a few drivers doing exactly this.
> 
> So if we want, we could have the following channel mapping:
> 
>   0 -> acin
>   1 -> vbus
>   2 -> pmic
>   3 -> gpio0
>   4 -> gpio1
>   5 -> ipsout
>   6 -> battery
> 
> Each channel could have mulitple entries in axp20x_adc_channels[],
> one for each type of reading. You might need multiple channels for
> the battery to cover charge and discharge currents.
> 
> Your callback functions would get a bit messier though.
> 
>>
>>>> [...]
>>>>>> +static int axp22x_adc_read_raw(struct iio_dev *indio_dev,
>>>>>> +                              struct iio_chan_spec const *channel, int *val,
>>>>>> +                              int *val2)
>>>>>> +{
>>>>>> +       struct axp20x_adc_iio *info = iio_priv(indio_dev);
>>>>>> +       int size = 12, ret;
>>>>>> +
>>>>>> +       switch (channel->channel) {
>>>>>> +       case AXP22X_BATT_DISCHRG_I:
>>>>>> +               size = 13;
>>>>>> +       case AXP22X_TEMP_ADC:
>>>>>> +       case AXP22X_BATT_V:
>>>>>> +       case AXP22X_BATT_CHRG_I:
>>>>>
>>>>> According to the datasheet, AXP22X_BATT_CHRG_I is also 13 bits wide.
>>>>>
>>>>
>>>> Where did you get that?
>>>>
>>>> Also, the datasheet is inconsistent:
>>>>  - 9.5 E-Gauge Fuel Gauge system => the min value is at 0x0 and the max
>>>> value at 0xfff for all channels, that's 12 bits.
>>>>  - 10.1.4 ADC Data => all channels except battery discharge current are
>>>> on 12 bits (8 high, 4 low).
>>>
>>> My datasheets (AXP221 v1.6, AXP221s v1.2, AXP223 v1.1, all Chinese) say
>>> in 10.1.4:
>>>
>>>   - 7A: battery charge current high 5 bits
>>>   - 7B: battery charge current low 8 bits
>>>   - 7C: battery discharge current high 5 bits
>>>   - 7D: battery discharge current low 8 bits
>>>
>>
>> AXP223 v1.1 in English in 10.1.4[1]:
>>     - 7A: battery charge current high 8 bits
>>     - 7B: battery charge current low 4 bits
>>     - 7C: battery discharge current high 8 bits
>>     - 7D: battery discharge current low 5 bits
>>
>> Note that it's 8 bits for high and 4/5 bits for low while you wrote 4/5
>> bits high and low 8 bits (typos or actually what's written in the
>> datasheet?).
> 
> Typo on my end, sorry. It's high 8bits and low 5/4 bits.
> 
> Apart from that, the Chinese and English versions don't match for the
> battery charge current. :(
> 
> Would it be possible for you to test this? As in, have the module running,
> and charging a battery, and have a multimeter in series with the battery
> to verify the readings.
> 
> Regards
> ChenYu
> 
>>
>> Hum.. from the reg reading function[2] I would say that the correct
>> formula is high on 8 bits and low on 4/5 bits.
>>
>> So hum.. what do we do?
>>
>> [1] http://dl.linux-sunxi.org/AXP/AXP223-en.pdf
>> [2] http://lxr.free-electrons.com/source/include/linux/mfd/axp20x.h#L564
>>
>>>>
>>>> [...]
>>>>>> +static int axp22x_read_raw(struct iio_dev *indio_dev,
>>>>>> +                          struct iio_chan_spec const *chan, int *val,
>>>>>> +                          int *val2, long mask)
>>>>>> +{
>>>>>> +       switch (mask) {
>>>>>> +       case IIO_CHAN_INFO_OFFSET:
>>>>>> +               *val = -2667;
>>>>>
>>>>> Datasheet says -267.7 C, or -2677 here.
>>>>>
>>>>
>>>> The formula in the datasheet is (in milli Celsius):
>>>>  processed = raw * 100 - 266700;
>>>>
>>>> while the IIO framework asks for a scale and an offset which are then
>>>> applied as:
>>>>  processed = (raw + offset) * scale;
>>>>
>>>> Thus by factorizing, we get:
>>>>  processed = (raw - 2667) * 100;
>>>
>>> What I meant was that your lower end value is off by one degree,
>>> -266.7 in your code vs -267.7 in the datasheet.
>>>
>>
>> Indeed. Thanks.
>>
>>>>
>>>> [...]
>>>>>> +static int axp20x_remove(struct platform_device *pdev)
>>>>>> +{
>>>>>> +       struct axp20x_adc_iio *info;
>>>>>> +       struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>>>>>> +
>>>>>> +       info = iio_priv(indio_dev);
>>>>>
>>>>> Nit: you could just reverse the 2 declarations above and join this
>>>>> line after struct axp20x_adc_iio *info;
>>>>>
>>>>>> +       regmap_write(info->regmap, AXP20X_ADC_EN1, 0);
>>>>>> +       regmap_write(info->regmap, AXP20X_ADC_EN2, 0);
>>>>>
>>>>> The existing VBUS power supply driver enables the VBUS ADC bits itself,
>>>>> and does not check them later on. This means if one were to remove this
>>>>> axp20x-adc module, the voltage/current readings in the VBUS power supply
>>>>> would be invalid. Some sort of workaround would be needed here in this
>>>>> driver of the VBUS driver.
>>>>>
>>>>
>>>> That would be one reason to migrate the VBUS driver to use the IIO
>>>> channels, wouldn't it?
>>>
>>> It is, preferably without changing the device tree.
>>>
>>
>> Yes, of course.
>>
>> Thanks,
>> Quentin
>>
>> --
>> Quentin Schulz, Free Electrons
>> Embedded Linux and Kernel engineering
>> http://free-electrons.com
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