Re: [PATCH 3/5] Documentation: dt: iio: document stm32 exti trigger
From: Fabrice Gasnier
Date: Fri Feb 03 2017 - 05:39:09 EST
On 02/02/2017 04:45 PM, Rob Herring wrote:
+Linus W
On Thu, Feb 2, 2017 at 3:19 AM, Fabrice Gasnier <fabrice.gasnier@xxxxxx> wrote:
On 02/01/2017 05:35 PM, Rob Herring wrote:
On Mon, Jan 30, 2017 at 02:57:41PM +0100, Fabrice Gasnier wrote:
Add dt documentation for st,stm32-exti-trigger.
EXTi gpio signal can be routed internally as trigger source for various
s/gpio/GPIO/
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.
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
---
.../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/
+IPs (e.g. for ADC or DAC conversions).
+
+Contents of a stm32 exti trigger root node:
Drop "root"
I'll fix these in V2.
+-------------------------------------------
+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.
Hi Rob,
Sorry, I don't get it. Can you clarify ?
What controls the GPIO line that is used for the trigger?
This can be anything connected to GPIO line, such as (on board)
push-button, external synchronization signal ...
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.
Sorry, muxing part (e.g. PA11, PB11...) isn't shown in above scheme.
GPIO is muxed via gpio/pinctrl driver.
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.
This is almost it, there are two stages.
- trigger starts conversion on device (e.g. ADC...) by hardware (no need
for interrupt on 1st stage, data isn't ready anyway).
- 2nd stage, end of conversion polls the trigger.
Just to summarize, rephrase, in case push button is used to trigger
conversions:
- 1st declare GPIO (to which push button is connected)
- GPIO is muxed into external interrupt (e.g. EXTI) by using pinctrl
and exti driver. This may be compared to a 'gpio_keys' up to this point.
- EXTI line is able to either generate an interrupt (not used here)
and/or start conversion as trigger line (that is used here).
- end of conversion does the actual trigger poll.
+- 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".
Oh... got it, thanks.
I'll update this.
Best Regards,
Fabrice
- 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.
+ (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
+ };
--
1.9.1