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Re: [PATCH v2 2/3] iio:adc:palmas: add DT support

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Am 05.10.2015 um 13:17 schrieb Mark Rutland <mark.rutland@arm.com>:

> On Sun, Oct 04, 2015 at 06:05:59PM +0200, H. Nikolaus Schaller wrote:
>> From: Marek Belisko <marek@goldelico.com>
>> 
>> Code was found at:
>> https://android.googlesource.com/kernel/tegra/+/a90856a6626d502d42c6e7abccbdf9d730b36270%5E%21/#F1
>> 
>> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
>> [Fixed minor typos + add channels list to documentation]
>> Signed-off-by: Marek Belisko <marek@goldelico.com>
>> ---
>> .../devicetree/bindings/iio/adc/palmas-gpadc.txt   | 46 +++++++++++++++++++
>> drivers/iio/adc/palmas_gpadc.c                     | 52 +++++++++++++++++++---
>> 2 files changed, 93 insertions(+), 5 deletions(-)
>> create mode 100644 Documentation/devicetree/bindings/iio/adc/palmas-gpadc.txt
>> 
>> diff --git a/Documentation/devicetree/bindings/iio/adc/palmas-gpadc.txt b/Documentation/devicetree/bindings/iio/adc/palmas-gpadc.txt
>> new file mode 100644
>> index 0000000..2149afe
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/palmas-gpadc.txt
>> @@ -0,0 +1,46 @@
>> +* Palmas general purpose ADC IP block devicetree bindings
>> +
>> +Channels list:
>> +	0 battery type
>> +	1 battery temp NTC (optional current source)
>> +	2 GP
>> +	3 temp (with ext. diode, optional current source)
>> +	4 GP
>> +	5 GP
>> +	6 VBAT_SENSE
>> +	7 VCC_SENSE
>> +	8 Backup Battery voltage
>> +	9 external charger (VCHG)
>> +	10 VBUS
>> +	11 DC-DC current probe (how does this work?)
>> +	12 internal die temp
>> +	13 internal die temp
>> +	14 USB ID pin voltage
>> +	15 test network
>> +
>> +Required properties:
>> +- compatible : Must be "ti,palmas-gpadc".
>> +
>> +Optional sub-nodes:
>> +ti,channel0-current-microamp: Channel 0 current in uA.
>> +	Values are rounded to derive 0uA, 5uA, 15uA, 20uA.
>> +ti,channel3-current-microamp: Channel 3 current in uA.
>> +	Valid are rounded to derive 0uA, 10uA, 400uA, 800uA.
> 
> It's only possible to configure channels 0 and 3 in this manner?

Yes. The other channels have no built-in current source, i.e. these
channels are special.

> 
>> +ti,enable-extended-delay: Enable extended delay.
> 
> What is this? When would I select it? Why does it belong in the DT
> rather than being a runtime option?

The chip allows to extend the time window between channel selection
and sampling by 400µs (according to data sheet). But for all channels
and not each one. As far as I understand, this is - depending on hardware
setup - to get more stable ADC readings.

Most channels have a fixed function (e.g. battery voltage, USB VBUS,
temperature NTC) so it can't be arbitrarily chosen and depends on how
the Palmas is embedded (it is a PMIC with a bank of ADCs and not a
general purpose ADC chip).

So I think it is really a hardware dependent parameter and not something
the user should be able to change.

> 
>> +Example:
>> +
>> +pmic {
>> +	compatible = "ti,twl6035-pmic", "ti,palmas-pmic";
>> +	...
>> +	gpadc {
>> +		compatible = "ti,palmas-gpadc";
>> +		interrupts = <18 0
>> +			      16 0
>> +			      17 0>;
>> +		ti,channel0-current-microamp = <5>;
>> +		ti,channel3-current-microamp = <10>;
>> +		};
>> +	};
>> +	...
>> +};
> 
> I thought you needed #iio-cells for encoding the channel?

Yes, we forgot (we don't have a client for it in our setup yet - so did not test :)

> 
> Mark.

Thanks,
Nikolaus Schaller

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[PATCH 0/3] Add Palmas iio gpadc "H. Nikolaus Schaller" <hns@goldelico.com> - 2015-09-23 14:50 +0200
  [PATCH v2 1/3] iio:adc: add iio driver for Palmas (twl6035/7) gpadc "H. Nikolaus Schaller" <hns@goldelico.com> - 2015-10-04 18:10 +0200
  [PATCH v2 0/3] Add Palmas iio gpadc "H. Nikolaus Schaller" <hns@goldelico.com> - 2015-10-05 08:20 +0200
    [PATCH v2 2/3] iio:adc:palmas: add DT support "H. Nikolaus Schaller" <hns@goldelico.com> - 2015-10-05 08:20 +0200
      Re: [PATCH v2 2/3] iio:adc:palmas: add DT support Laxman Dewangan <ldewangan@nvidia.com> - 2015-10-05 13:10 +0200
    [PATCH v2 1/3] iio:adc: add iio driver for Palmas (twl6035/7) gpadc "H. Nikolaus Schaller" <hns@goldelico.com> - 2015-10-05 08:20 +0200
      Re: [PATCH v2 1/3] iio:adc: add iio driver for Palmas (twl6035/7)  gpadc kbuild test robot <lkp@intel.com> - 2015-10-05 09:00 +0200
      [PATCH] iio:adc: fix platform_no_drv_owner.cocci warnings kbuild test robot <lkp@intel.com> - 2015-10-05 09:00 +0200
      Re: [PATCH v2 1/3] iio:adc: add iio driver for Palmas (twl6035/7)  gpadc Laxman Dewangan <ldewangan@nvidia.com> - 2015-10-05 13:00 +0200
      Re: [PATCH v2 1/3] iio:adc: add iio driver for Palmas (twl6035/7)  gpadc Jonathan Cameron <jic23@kernel.org> - 2015-10-11 16:30 +0200
        Re: [PATCH v2 1/3] iio:adc: add iio driver for Palmas (twl6035/7)  gpadc Lee Jones <lee.jones@linaro.org> - 2015-10-13 10:20 +0200
    [PATCH v2 3/3] ARM: dts: omap5-uevm: enable iio gpadc for Palmas "H. Nikolaus Schaller" <hns@goldelico.com> - 2015-10-05 08:20 +0200
  Re: [PATCH v2 2/3] iio:adc:palmas: add DT support Mark Rutland <mark.rutland@arm.com> - 2015-10-05 13:20 +0200
    Re: [PATCH v2 2/3] iio:adc:palmas: add DT support "H. Nikolaus Schaller" <hns@goldelico.com> - 2015-10-05 16:30 +0200

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