[PATCH 1/6] dt-bindings: mfd: Add ST Multi-Function eXpander driver

On Mon, Feb 19, 2018 at 9:59 AM, Amelie DELAUNAY [off-list ref] wrote:

On 02/19/2018 12:19 AM, Rob Herring wrote:

quoted

On Thu, Feb 08, 2018 at 03:27:32PM +0100, Amelie Delaunay wrote:

quoted

This patch adds documentation of device tree bindings for the
STMicroelectronics Multi-Function eXpander (MFX).

Signed-off-by: Amelie Delaunay <redacted>
---
  Documentation/devicetree/bindings/mfd/st-mfx.txt | 51 ++++++++++++++++++++++++
  1 file changed, 51 insertions(+)
  create mode 100644 Documentation/devicetree/bindings/mfd/st-mfx.txt

diff --git a/Documentation/devicetree/bindings/mfd/st-mfx.txt b/Documentation/devicetree/bindings/mfd/st-mfx.txt
new file mode 100644
index 0000000..423d800
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/st-mfx.txt

@@ -0,0 +1,51 @@
+STMicroelectronics Multi-Function eXpander
+
+ST Multi-Function eXpander (MFX) is a slave controller using I2C for
+communication with the main MCU. Its main features are gpio expansion, main
+MCU IDD measurement (IDD is the amount of current that flows through VDD)
+and resistive touchscreen controller.

You don't have to implement all the drivers now, but please completely
describe the device. As is, there is no reason to have a child GPIO
node.

The MFD driver will be abandoned as only GPIO part is used. I'll send a
V2 soon.

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+
+Required properties:
+- compatible: must be "st,mfx"

Kind of generic. Only 1 single version ever?

"st-mfx" compatible will disappear in V2 (we keep only GPIO driver). MFX
version can be read in MFX FW_VERSION register. So do I keep
"st,mfx-gpio" compatible or you want to see mfx version ?

That sounds a bit worrying. The other functions will *never* get
accessed? The DT should reflect the h/w including any future needs,
not just what you have a driver for today.

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+- reg: I2C address of the device
+- interrupts: interrupt triggered by MFX_IRQ_OUT signal
+- interrupt-parent: interrupt controller MFX is connected to
+- interrupt-controller: marks the device as an interrupt controller
+- #interrupt-cells: should be <1>, index of the interrupt within the
+  controller, in accordance with the "one cell" variant of
+  <devicetree/bindings/interrupt-controller/interrupt.txt>
+
+Optional nodes:
+
+* GPIO eXpander
+MFX provides 16 programmable GPIOs, and it is also possible to recover 8
+alternate GPIOs if the main functions are not used (touchscreen controller and
+IDD measurement not enabled).
+
+Required properties:
+- compatible : must be "st,mfx-gpio"
+- interrupt-parent : must be <&mfx>

Not necessary. A parent node with 'interrupt-controller' property is the
interrupt's parent.

I will keep it in mind.

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+- interrupts = must be <0>
+- gpio-controller: marks the device node as a GPIO controller
+- #gpio-cells: should be <2>, the first cell is the GPIO offset on this GPIO
+  controller, the second cell is the gpio flags in accordance with
+  <dt-bindings/gpio/st-mfx-gpio.h>.

Custom flags? Use standard flags.

DT binding headers should be part of this patch.

Custom flags because MFX GPIOs have several types:
- Output open drain with internal pull-up resistor
- Output open drain without internal pull-up resistor
- Output push pull without internal pull resistor
- Input with internal pull-up resistor
- Input with internal pull-down resistor
- Input floating
- Input analog.
Standard flags don't have pull up or down information. That's why I am
using custom flags, they overloads standard flags.

I'll leave this one to Linus to comment on.

I will add DT bindings header in this patch V2.