linux-kernel - Re: [PATCH v5 1/2] iio: adc: vf610: implement configurable conversion modes

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Message-ID: <557D6184.90105@kernel.org>
Date:	Sun, 14 Jun 2015 12:12:04 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Stefan Agner <stefan@...er.ch>, Rob Herring <robherring2@...il.com>
CC:	Shawn Guo <shawn.guo@...aro.org>, kernel@...gutronix.de,
	knaack.h@....de, Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Fugang Duan <B38611@...escale.com>, maitysanchayan@...il.com,
	devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/2] iio: adc: vf610: implement configurable conversion
 modes

On 08/06/15 21:07, Stefan Agner wrote:
> On 2015-06-08 19:49, Rob Herring wrote:
>> On Wed, May 27, 2015 at 7:47 AM, Stefan Agner <stefan@...er.ch> wrote:
>>> Support configurable conversion mode through sysfs. So far, the
>>> mode used was low-power, which is enabled by default now. Beside
>>> that, the modes normal and high-speed are selectable as well.
>>>
>>> Use the new device tree property which specifies the maximum ADC
>>> conversion clock frequencies. Depending on the mode used, the
>>> available resulting conversion frequency are calculated
>>> dynamically.
>>>
>>> Acked-by: Fugang Duan <B38611@...escale.com>
>>> Signed-off-by: Stefan Agner <stefan@...er.ch>
>>> ---
>>>  Documentation/ABI/testing/sysfs-bus-iio-vf610      |   7 +
>>>  .../devicetree/bindings/iio/adc/vf610-adc.txt      |   9 ++
>>>  drivers/iio/adc/vf610_adc.c                        | 146 +++++++++++++++------
>>>  3 files changed, 120 insertions(+), 42 deletions(-)
>>>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-vf610
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-vf610 b/Documentation/ABI/testing/sysfs-bus-iio-vf610
>>> new file mode 100644
>>> index 0000000..ecbc1f4
>>> --- /dev/null
>>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-vf610
>>> @@ -0,0 +1,7 @@
>>> +What:          /sys/bus/iio/devices/iio:deviceX/conversion_mode
>>> +KernelVersion: 4.2
>>> +Contact:       linux-iio@...r.kernel.org
>>> +Description:
>>> +               Specifies the hardware conversion mode used. The three
>>> +               available modes are "normal", "high-speed" and "low-power",
>>> +               where the last is the default mode.
>>> diff --git a/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt b/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
>>> index 1a4a43d..3eb40e2 100644
>>> --- a/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
>>> +++ b/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
>>> @@ -11,6 +11,13 @@ Required properties:
>>>  - clock-names: Must contain "adc", matching entry in the clocks property.
>>>  - vref-supply: The regulator supply ADC reference voltage.
>>>
>>> +Recommended properties:
>>> +- fsl,adck-max-frequency: Maximum frequencies according to datasheets operating
>>> +  requirements. Three values are required, depending on conversion mode:
>>> +  - Frequency in normal mode (ADLPC=0, ADHSC=0)
>>> +  - Frequency in high-speed mode (ADLPC=0, ADHSC=1)
>>> +  - Frequency in low-power mode (ADLPC=1, ADHSC=0)
>>
>> Why is this "adck" rather than "adc"?
> 
> That is the name of the clock according to the reference manual and data
> sheet.
> 
>> How is this related to today's patch adding min-sample-time?
> 
> It is related in that this clock is the base to calculate the sampling
> time, but otherwise not really related. Afaik, not respecting the
> maximum clock frequency is probably more a issue for the SAR part of the
> ADC.
Rob, are you happy with Stefan's responses?
> 
> --
> Stefan
> 
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