How to set correctly GPIO flags in dts files?

[TRay]

Hi,

 

I managed to make w1-GPIO work in Orange Pi Zero v3 for, for example, the DS18B20 sensor.

 

However, I have some doubts about setting the GPIO flags for w1-gpio. Many examples provide flags in the form

 

gpios = <&pio 0 7 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;

 

but in the dts file when I use this form it does not work (syntax error) so I have to provide the flags in digital form.

 

A description of flags and bits is here

 

https://elixir.bootlin.com/linux/v6.6.30/source/include/dt-bindings/gpio/gpio.h

 

If I would like to set GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN then the digital value for these bits will be for set bits: 0110000 =  48

 

because GPIO_OPEN_DRAIN it is (GPIO_SINGLE_ENDED | GPIO_LINE_OPEN_DRAIN)

 

Please help me and confirm whether I understood it correctly I wanted to get rid of the message in the logs for w1-gpio

 

[ 4.994183] gpio-74 (onewire@0): enforced open drain please flag it properly in DT/ACPI DSDT/board file

 

which understands that I need to set the GPIO flag GPIO_OPEN_DRAIN in the dts file

 

 

I see one problem with this source https://www.kernel.org/doc/Documentation/devicetree/bindings/gpio/gpio.txt

where a number of bits to set is 6 in source https://elixir.bootlin.com/linux/v6.6.30/source/include/dt-bindings/gpio/gpio.h

number of bits to set is 7

 

 

I hope I posted this question in the right section, if not please move it

Edited May 17, 2024 by TRay

[TRay]

Reading many others documents about OPEN DRAIN flag , OZPI v3 and others like Raspberry Pi don't support Open DRAIN, but they should work in emulated mode, switching between input and output-driving-low. So for this reason if we set flag for GPIO with OPEN DARIN it looks not influence and not need setting this flag for w1-gpio for this SBC

 

 

Edited May 17, 2024 by TRay

[firepower]

/* Bit 0 express polarity */
#define GPIO_ACTIVE_HIGH 0
#define GPIO_ACTIVE_LOW 1

/* Bit 1 express single-endedness */
#define GPIO_PUSH_PULL 0
#define GPIO_SINGLE_ENDED 2

/* Bit 2 express Open drain or open source */
#define GPIO_LINE_OPEN_SOURCE 0
#define GPIO_LINE_OPEN_DRAIN 4

/*
* Open Drain/Collector is the combination of single-ended open drain interface.
* Open Source/Emitter is the combination of single-ended open source interface.
*/
#define GPIO_OPEN_DRAIN (GPIO_SINGLE_ENDED | GPIO_LINE_OPEN_DRAIN)
#define GPIO_OPEN_SOURCE (GPIO_SINGLE_ENDED | GPIO_LINE_OPEN_SOURCE)

/* Bit 3 express GPIO suspend/resume and reset persistence */
#define GPIO_PERSISTENT 0
#define GPIO_TRANSITORY 8

 

when combining add the bits #define GPIO_OPEN_DRAIN (GPIO_SINGLE_ENDED | GPIO_LINE_OPEN_DRAIN)  is 2+4= 6

 

 

gpios = <&pio 0 7 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;  

or

gpios = <&pio 0 7 4>;