From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [RFC 1/8] dt-bindings: mfd: Add Altera Arria10 System Resource Chip bindings Date: Tue, 19 Apr 2016 18:48:35 -0700 Message-ID: <5716DFF3.6080905@roeck-us.net> References: <1459278791-3646-1-git-send-email-tthayer@opensource.altera.com> <1459278791-3646-2-git-send-email-tthayer@opensource.altera.com> <20160330113532.GI3323@x1> <57111E8B.1040503@opensource.altera.com> <20160418074540.GB3346@x1> <5714F942.5040309@opensource.altera.com> <20160419072358.GB3222@x1> <571642DA.2060903@opensource.altera.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <571642DA.2060903@opensource.altera.com> Sender: linux-hwmon-owner@vger.kernel.org To: tthayer@opensource.altera.com, Lee Jones Cc: linus.walleij@linaro.org, gnurou@gmail.com, jdelvare@suse.com, robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, dinguyen@opensource.altera.com, linux-gpio@vger.kernel.org, linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org On 04/19/2016 07:38 AM, Thor Thayer wrote: > > > On 04/19/2016 02:23 AM, Lee Jones wrote: >> On Mon, 18 Apr 2016, Thor Thayer wrote: >> >>> Hi Lee, >>> >>> On 04/18/2016 02:45 AM, Lee Jones wrote: >>>> On Fri, 15 Apr 2016, Thor Thayer wrote: >>>>> On 03/30/2016 06:35 AM, Lee Jones wrote: >>>>>> On Tue, 29 Mar 2016, tthayer@opensource.altera.com wrote: >>>>>> >>>>>>> From: Thor Thayer >>>>>>> >>>>>>> The Altera Arria10 Devkit System Resource chip is a Multi-Function >>>>>>> Device, it has two subdevices: >>>>>>> - GPIO >>>>>>> - HWMON >>>>>>> >>>>>>> This patch adds documentation for the Altera A10-SR DT bindings. >>>>>>> >>>>>>> Signed-off-by: Thor Thayer >>>>>>> --- >>>>>>> .../devicetree/bindings/mfd/altera-a10sr.txt | 35 ++++++++++++++++++++ >>>>>>> 1 file changed, 35 insertions(+) >>>>>>> create mode 100644 Documentation/devicetree/bindings/mfd/altera-a10sr.txt >>>>>>> >>>>>>> diff --git a/Documentation/devicetree/bindings/mfd/altera-a10sr.txt b/Documentation/devicetree/bindings/mfd/altera-a10sr.txt >>>>>>> new file mode 100644 >>>>>>> index 0000000..564c761 >>>>>>> --- /dev/null >>>>>>> +++ b/Documentation/devicetree/bindings/mfd/altera-a10sr.txt >>>>>>> @@ -0,0 +1,35 @@ >>>>>>> +* Altera Arria10 Development Kit System Resource Chip >>>>>>> + >>>>>>> +Required parent device properties: >>>>>>> +- compatible : "altr,altr_a10sr" >>>>>>> +- spi-max-frequency : Maximum SPI frequency. >>>>>>> +- reg : the SPI Chip Select address for the Arria10 System Resource chip >>>> >>>> [...] >>>> >>>>>>> + a10sr_hwmon: a10sr_hwmon { >>>>>> >>>>>> Device type only please. >>>>>> >>>>> I need to revisit where this will live (hwmon does not seem to be >>>>> the correct place) so it will change but I can follow the format >>>>> above if it is correct. >>>> >>>> BTW, "hwmon" is a subsystem in Linux, therefore is a Linuxism and is >>>> not allowed in DT. What does the device *actually* do? >>>> >>> >>> OK. I'll be careful not to introduce the Linux subsystem name. >>> >>> This module indicates whether the power supplies are at the correct >>> voltage. It uses a boolean instead of giving an actual voltage value >>> as required by HWMON. In other words it is a comparator instead of >>> an Analog-to-Digital Converter. >>> >>> I could call it a power supply supervisor or voltage status monitor >>> but it only acts in a passive role. There is no output to trigger an >>> error - only polling, so supervisor doesn't seem like a good name. >>> >>> Maybe something like this? >>> >>> power_supply_status { >>> compatible = "altr,a10sr-hwmon"; >>> } >>> >>> Thanks for reviewing and helping me figure out the device tree naming. >> >> Does it have its own address space? How complex is the device? Not >> very, by the sounds of it. In which case, does it really need its own >> driver? >> > Yes, you are correct that the voltage status is not very complex but I'd need a driver to expose these signals. > A completely different option might be to expose the signals as gpio pins. Guenter > I initially started with an MFD because it was similar to the other MFD drivers. The device has GPI, GPO, voltage status, device enables, device present indications, and device resets. > > There is a discussion now on where the voltage status driver should live (iio/ , hwmon/, misc/). It isn't clear to me where the device enables, device present indications and voltage status would go. I'm leaning toward a driver in the misc/ directory that would cover all of these. In that case, this wouldn't be a MFD driver. > > Any thoughts or suggestions? > > Thanks, > > Thor >