Re: [PATCH 1/3] iio: mxs-lradc: Add regulators for current sources

Hi Stefan!

On 03.05.2016 13:07, Stefan Wahren wrote:

Am 22.04.2016 um 15:52 schrieb Harald Geyer:

quoted

The hardware has two current sources ISRC0 and ISRC1 to allow 
measuring
resistors without additional circuitry. This commit makes them 
available
as regulators.

Tested on an imx233-olinuxino board.

Signed-off-by: Harald Geyer <redacted>
---
The current regulator API doesn't fit this type of device very well: 
Typically
consumers will want to set a defined current, ie. min_uA == max_uA, 
but they
can't without help from configuration data, because the valid values 
aren't
reported by the API for current regulators. I have been thinking 
about
extending the API, but currently AFAIK no such consumers exist and 
most
users, like myself, will force the regulator to a defined value in
devicetree anyway.

 .../bindings/staging/iio/adc/mxs-lradc.txt         |  29 ++++
 drivers/iio/adc/Kconfig                            |   1 +
 drivers/iio/adc/mxs-lradc.c                        | 152 
+++++++++++++++++++++
 3 files changed, 182 insertions(+)

diff --git 

a/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt 
b/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt
index 555fb11..983952c 100644
--- 
a/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt
+++ 
b/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt

@@ -19,6 +19,15 @@ Optional properties:
 - fsl,settling: delay between plate switch to next sample. Allowed 

value is
                 1 ... 2047. It counts at 2 kHz and its default is
                 10 (= 5 ms)
+- ISRC0: A node describing the regulator of internal current source 
0
+- ISRC1: A node describing the regulator of internal current source 
1
+
+Required properties for the ISRCx sub-nodes:
+- regulator-max-microamp: See standard regulator binding 
documentation.
+                          Valid values are from 0 to 300 in steps 
of 20.
+
+Optional properties for the ISRCx sub-nodes:
+Any standard regulator properties that apply to current regulators.

 Example for i.MX23 SoC:

@@ -31,6 +40,16 @@ Example for i.MX23 SoC:
 		fsl,ave-ctrl = <4>;
 		fsl,ave-delay = <2>;
 		fsl,settling = <10>;
+
+		isrc_lradc0: ISRC0 {
+			regulator-max-microamp = <300>;
+		};
+
+		isrc_lradc1: ISRC1 {
+			regulator-max-microamp = <120>;
+			regulator-min-microamp = <120>;
+			regulator-always-on;
+		};

IMHO the binding should represent the direct connection between the
current source and the physical channel. I think a node label isn't
enough. Unfortunately i don't have an idea to do it the "right way".

I strictly followed the names of the data sheet here: imx23 and imx28
reference manuals both call the current sources ISRC0 and ISRC1 even
if they are attached to different channels of the ADC. I think
inventing some ISRC6 for imx28 would do more harm then good.

quoted

 	};

 Example for i.MX28 SoC:

@@ -44,4 +63,14 @@ Example for i.MX28 SoC:
 		fsl,ave-ctrl = <4>;
 		fsl,ave-delay = <2>;
 		fsl,settling = <10>;
+
+		isrc_lradc0: ISRC0 {
+			regulator-max-microamp = <300>;
+		};
+
+		isrc_lradc6: ISRC1 {
+			regulator-max-microamp = <120>;
+			regulator-min-microamp = <120>;
+			regulator-always-on;
+		};
 	};

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 5937030..1968d1c 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig

@@ -319,6 +319,7 @@ config MXS_LRADC
         tristate "Freescale i.MX23/i.MX28 LRADC"
         depends on (ARCH_MXS || COMPILE_TEST) && HAS_IOMEM
         depends on INPUT
+        depends on REGULATOR

Any chance to avoid this dependency for an optional feature?

I haven't looked into it yet, but I expect that that the mfd
conversion will avoid this neatly.

Thanks,
Harald

Stefan

quoted

         select STMP_DEVICE
         select IIO_BUFFER
         select IIO_TRIGGERED_BUFFER

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