From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4+5iI2vKwKW0NPxnr5E24CuOT33s7QtUz7kPEoMJ7cbnyAo+x6MsEgKjjxzSjhVp0en0ryR ARC-Seal: i=1; a=rsa-sha256; t=1523206239; cv=none; d=google.com; s=arc-20160816; b=cY5U4qS9Z7V/MOFigJAvG3eAGchyiMCxMD1d0hUmKxJXq84FCJL/WsiD8SC2PrG8D5 gg8J6eFhsfK4MwRtphdlPZO7pf66v1pU9EtpbKpBaecKr3IPPV/LrrKnT+f3GeM4gBEl ecmfX2Ywg4IMmiWdMBZFdwG62THXp3XsjoUF8ooF99wBW9bQjalqtFGd7AHj1YBaMx1p /VANGYT0ecW9brLBXG+Gz2LZsch5eSe4Z/YaxzI/a7Z7Ojjz++jlDB03tjWq5VCAqFLU 1IWg0zuBmmllrXx2aH5vUJJwzGg4C8UrjQW2vb25AZQ2CA6uVwg5K4MtOgMK4m9S5Eo/ fbKA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:dmarc-filter :arc-authentication-results; bh=8GW8Dx86SzSr71EqKmCgzejAW8BQCxy4oHOsRqr+FdY=; b=WYzgJB9HRJV4p5Y6UFoJWtKVNjZZPwPzNMMijZRQy84kAgPeB/JnvOwlp6R7to+/gc BgE1cXMXkfZGvNrh1A+GW7vimA20ueGcwVq2UhWVX8xmK1T9pLwE69mVtJo7NAH8H2Bk qJxTIg1XaTc7dqyBQkZynSGjw5C+LXCPJFG2s/Hoq+nPgM/qe5rTM+LrGMykk6GpB0MQ VEG9ofEKNxBeTwtcpCO2mZXT9Q9MqRcOOalKRG7M7ExGg3/RYT7LBB4qdgzNT/eS0FoA UGHy+6YMplSsXPZLLk7okQcmW4/MXGyyZz2e+Yaa/68a6I5lZ/pQOJF3t/ayo6n+CHRK qrpA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of jic23@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=jic23@kernel.org Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of jic23@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=jic23@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C2FD21738 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jic23@kernel.org Date: Sun, 8 Apr 2018 17:50:31 +0100 From: Jonathan Cameron To: Peter Rosin Cc: linux-kernel@vger.kernel.org, Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , Rob Herring , Mark Rutland , "David S. Miller" , Mauro Carvalho Chehab , Greg Kroah-Hartman , Linus Walleij , Andrew Morton , Randy Dunlap , Michael Hennerich , Phil Reid , linux-iio@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v2 1/2] dt-bindings: iio: afe: add current-sense-cuicuit and voltage-divider Message-ID: <20180408175031.4945e2d7@archlinux> In-Reply-To: <20180403153635.8228-2-peda@axentia.se> References: <20180403153635.8228-1-peda@axentia.se> <20180403153635.8228-2-peda@axentia.se> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1596739881382169628?= X-GMAIL-MSGID: =?utf-8?q?1597197506236780541?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Tue, 3 Apr 2018 17:36:34 +0200 Peter Rosin wrote: circuit in the patch title is spelled wrong. > An ADC is often used to measure other quantities indirectly. These > bindings describe two cases, a current through a sense resistor, and > a "big" voltage measured with the help of a voltage divider. > > Signed-off-by: Peter Rosin Will definitely be wanting wide opinions on this one - Rob in particularly for the binding side. One comment inline. What we have here is nice and generic, but is it what would be 'expected' for current sense circuit? Should we also be more specific in the naming. There are lots of options for current sense circuits and this is just the simplest (current loop for example). One option would be to use current-sense-shunt perhaps? https://en.wikipedia.org/wiki/Current_sensing_techniques Gives a few that I didn't think of beyond current loops etc. > --- > .../bindings/iio/afe/current-sense-circuit.txt | 45 ++++++++++++++++++++++ > .../bindings/iio/afe/voltage-divider.txt | 45 ++++++++++++++++++++++ > MAINTAINERS | 7 ++++ > 3 files changed, 97 insertions(+) > create mode 100644 Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt > create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt > > diff --git a/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt b/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt > new file mode 100644 > index 000000000000..0bc7d89387c0 > --- /dev/null > +++ b/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt > @@ -0,0 +1,45 @@ > +Current Sense Curcuit > +===================== > + > +When an io-channel measures the voltage over a current sense resistor, > +the interesting mesaurement is often the current through the resistor, > +not the voltage over it. This binding describes such a current sense > +curcuit. > + > +Required properties: > +- compatible : "current-sense-circuit" > +- io-channels : Channel node of a voltage io-channel. > + > +Optional properties: > +- numerator : The io-channel scale is multiplied by this value (default 1). > +- denominator : The io-channel scale is divided by this value (default 1). > + > +Example: > +The system current is measured by measuring the voltage over a > +3.3 ohms sense resistor. Hmm. It sort of feels like the binding doesn't really reflect the hardware as directly as it might. Should we be explicitly having the resistance in this case? (with some more mapping logic needed in the driver to figure out the scaling this causes). > + > +sysi { > + compatible = "current-sense-circuit"; > + io-channels = <&tiadc 0>; > + > + /* Divide the ADC voltage by 33/10 (i.e. 3.3) to get the current. */ > + numerator = <10>; > + denominator = <33>; > +}; > + > +&i2c { > + tiadc: adc@48 { > + compatible = "ti,ads1015"; > + reg = <0x48>; > + #io-channel-cells = <1>; > + > + #address-cells = <1>; > + #size-cells = <0>; > + > + channel@0 { /* IN0,IN1 differential */ > + reg = <0>; > + ti,gain = <1>; > + ti,datarate = <4>; > + }; > + }; > +}; > diff --git a/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt > new file mode 100644 > index 000000000000..fd4a215d9e6d > --- /dev/null > +++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt > @@ -0,0 +1,45 @@ > +Voltage divider > +=============== > + > +When an io-channel measures the midpoint of a voltage divider, the > +interesting voltage is often the voltage over the full resistance > +of the divider. This binding describes the voltage divider in such > +a curcuit. > + > +Required properties: > +- compatible : "voltage-divider" > +- io-channels : Channel node of a voltage io-channel. > + > +Optional properties: > +- numerator : The io-channel scale is multiplied by this value (default 1). > +- denominator : The io-channel scale is divided by this value (default 1). > + > +Example: > +The system voltage is circa 12V, but divided down with a 22/200 > +voltage divider to adjust it to the ADC range. > + > +SYSV ADC GND > + + + + > + | .-----. | .----. | > + '--| 200 |-+-| 22 |--' > + '-----' '----' > + > +sysv { > + compatible = "voltage-divider"; > + io-channels = <&maxadc 1>; > + > + /* Multiply the ADC voltage by 222/22 to get the system voltage. */ > + numerator = <222>; /* 200 + 22 */ > + denominator = <22>; > +}; > + > +&spi { > + maxadc: adc@0 { > + compatible = "maxim,max1027"; > + reg = <0>; > + #io-channel-cells = <1>; > + interrupt-parent = <&gpio5>; > + interrupts = <15 IRQ_TYPE_EDGE_RISING>; > + spi-max-frequency = <1000000>; > + }; > +}; > diff --git a/MAINTAINERS b/MAINTAINERS > index 36a28e979e9a..9dbe5019c6bd 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -6889,6 +6889,13 @@ F: drivers/staging/iio/ > F: include/linux/iio/ > F: tools/iio/ > > +IIO UNIT CONVERTER > +M: Peter Rosin > +L: linux-iio@vger.kernel.org > +S: Maintained > +F: Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt > +F: Documentation/devicetree/bindings/iio/afe/voltage-divider.txt > + > IKANOS/ADI EAGLE ADSL USB DRIVER > M: Matthieu Castet > M: Stanislaw Gruszka