+Linus W

On Thu, Feb 2, 2017 at 3:19 AM, Fabrice Gasnier [off-list ref] wrote:

On 02/01/2017 05:35 PM, Rob Herring wrote:

quoted

On Mon, Jan 30, 2017 at 02:57:41PM +0100, Fabrice Gasnier wrote:

quoted

Add dt documentation for st,stm32-exti-trigger.
EXTi gpio signal can be routed internally as trigger source for various

s/gpio/GPIO/

quoted

IPs (e.g. for ADC or DAC conversions).

Please use "dt-bindings: iio:" for the subject prefix.

Hi Rob,

I'll fix this in V2.

quoted

quoted

Signed-off-by: Fabrice Gasnier <redacted>
---
 .../bindings/iio/trigger/st,stm32-exti-trigger.txt      | 17
+++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/iio/trigger/st,stm32-exti-trigger.txt

diff --git
a/Documentation/devicetree/bindings/iio/trigger/st,stm32-exti-trigger.txt
b/Documentation/devicetree/bindings/iio/trigger/st,stm32-exti-trigger.txt
new file mode 100644
index 0000000..ebf2645

--- /dev/null
+++

b/Documentation/devicetree/bindings/iio/trigger/st,stm32-exti-trigger.txt

@@ -0,0 +1,17 @@
+STMicroelectronics STM32 EXTI trigger bindings
+
+EXTi gpio signal can be routed internally as trigger source for various

s/gpio/GPIO/

quoted

+IPs (e.g. for ADC or DAC conversions).
+
+Contents of a stm32 exti trigger root node:

Drop "root"

I'll fix these in V2.

quoted

quoted

+-------------------------------------------
+Required properties:
+- compatible: Should be "st,stm32-exti-trigger"

This whole binding looks a bit suspicious. Is this actually a h/w block?
What makes it stm32 specific? Seems like the gpio properties should just
be part of the ADC or DAC that they trigger.

Please let me explain in more details.
I think best is I add following documentation in binding. Something like:

GPIO + EXTI controller side | ADC side (input trigger MUX, same for DAC)
                            |
       IIO trigger         --->         IIO device
                            |                  __________
                            |          inX  --|          \
                            |          ...  --|  SAR ADC  |-->
        __                  |         __      |__________/
PA11 --|  \                 | TIMx --|  \   trigger   ^
PB11 --|   |                  ...  --|   }----------->'
...  --|   }---- EXTI11 ---------->--|__/
     --|   |                |
PJ11 --|__/                 |

In fact, this driver configures GPIO and EXTI controllers (left side of
above scheme), and it registers corresponding trigger in IIO. Then it can be
used by other IPs registered as IIO devices.

I think this should be outside of ADC or DAC IIO device drivers, to live in
separate IIO trigger driver. It will avoid duplicating code (e.g. PATCH 4)
into several IIO device drivers.

Is it ok to declare this as separate IIO trigger driver?

Drivers and DT nodes are not necessarily 1 to 1.

What controls the GPIO line that is used for the trigger?

Maybe Jonathan could also advise on this ?

As I see it, this is stm32 specific, as any GPIO bank, (e.g. PA11,
PB11...) can be selected to generate (EXTI11) hardware trigger signal.

This seems more like a pinmux'ing issue than a GPIO. This isn't really
a GPIO if it is routed to a h/w control.

A -gpios property for a trigger would make sense if you had a driver
handling GPIO interrupts to generate IIO triggers. This seems to be
just mux control.

quoted

quoted

+- extiN-gpio: optional gpio line that may be used as external trigger
source

-gpios is the preferred form.

I apologize, I didn't make it clear in the first place. Please let me
rephrase. Is bellow description more suitable ?

What I mean is the property name is wrong. It should be "extiN-gpios".

- extiN-gpio: One or several named GPIO lines that may be used as
  external trigger source by STM32 ADC, DAC. N may be 0..15.
  For example, on stm32f4, exti11-gpio can trig ADC, exti9-gpio can
  trig DAC.

quoted

quoted

+  (e.g. N may be 0..15. For example, exti11-gpio can trig ADC on
stm32f4).
+
+Example:
+       triggers {
+               compatible = "st,stm32-exti-trigger";
+               exti11-gpio=<&gpioa 11 0>;

spaces around the "=".

I'll fix it in V2, and also add example for more that one EXTI trigger:

        triggers {
                compatible = "st,stm32-exti-trigger";
                exti9-gpio = <&gpioa 9 0>;
                exti11-gpio = <&gpioa 11 0>;
                ...
        };

Above binding can typically be used in board dt, in case on-board gpio is
connected/used as trigger source for IIO device (STM32 ADC/DAC).

Please let me know if this clarifies, so I'll do necessary changes in V2.

Many thanks for your review.
Best Regards,
Fabrice

quoted

quoted

+       };
--
1.9.1