Re: [PATCH v3 0/2] gpio: add generic gpio input multiplexer

[Drew Fustini <drew@beagleboard.org>]

On Mon, May 17, 2021 at 07:58:45PM +0300, Mauri Sandberg wrote:
> Hello all!
> 
> This patch set is closely related to another thread at [4], which I abandoned
> against better judgement and created this one.
> 
> Here I am sending revised versions of the patches. It builds on v2 and adopts 
> managed device resources as suggested by Andy on the thread mentioned
> above [5].
> 
> I have tested the functionality on a NXP 74HC153 dual 4-way muxer. Drew, did
> you find the time to have a go with this [6] and if so, did it work as expected?
> 
> Thanks,
> Mauri
> 
> [4] https://www.spinics.net/lists/linux-gpio/msg58573.html
> [5] https://www.spinics.net/lists/linux-gpio/msg60160.html
> [6] https://www.spinics.net/lists/linux-gpio/msg60159.html
> 
> 
> Mauri Sandberg (2):
>   dt-bindings: gpio-mux-input: add documentation
>   gpio: gpio-mux-input: add generic gpio input multiplexer
> 
>  .../bindings/gpio/gpio-mux-input.yaml         |  75 +++++++++++
>  drivers/gpio/Kconfig                          |  16 +++
>  drivers/gpio/Makefile                         |   1 +
>  drivers/gpio/gpio-mux-input.c                 | 124 ++++++++++++++++++
>  4 files changed, 216 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-mux-input.yaml
>  create mode 100644 drivers/gpio/gpio-mux-input.c
> 
> 
> base-commit: 6453b9532b5f77d19837b159c4d074f0af9f141b
> -- 
> 2.25.1

Tested-by: Drew Fustini <drew@beagleboard.org>
Reviewed-by: Drew Fustini <drew@beagleboard.org>

I have wired up the TI CD74HC153E to a BeagleBone Black:

  S0: P8_7
  S1: P8_8

  1Y: P8_10
  2Y: P8_9

I added this to arch/arm/boot/dts/am335x-boneblack.dts

  mux: mux-controller {
          compatible = "gpio-mux";
          #mux-control-cells = <0>;

          mux-gpios = <&gpio2 2 GPIO_ACTIVE_HIGH>, /* S0: P8_7 */
                      <&gpio2 3 GPIO_ACTIVE_HIGH>  /* S1: P8_8 */;
  };

  gpio8: key-mux1 {
          compatible = "gpio-mux-input";
          mux-controls = <&mux>;

          gpio-controller;
          #gpio-cells = <2>;

          // GPIOs used by this node, mux pin
          pin-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>; /* 2Y: P8_9 */
  };

  gpio9: key-mux2 {
          compatible = "gpio-mux-input";
          mux-controls = <&mux>;

          gpio-controller;
          #gpio-cells = <2>;

          // GPIOs used by this node, mux pin
          pin-gpios = <&gpio2 4 GPIO_ACTIVE_HIGH>; /* 1Y: P8_10 */
  };


The two new gpiochips appear:

  root@beaglebone:~# gpiodetect
  gpiochip0 [gpio-0-31] (32 lines)
  gpiochip1 [gpio-32-63] (32 lines)
  gpiochip2 [gpio-64-95] (32 lines)
  gpiochip3 [gpio-96-127] (32 lines)
  gpiochip4 [key-mux1] (4 lines)
  gpiochip5 [key-mux2] (4 lines)
  
The mux pins and input pins are connected to lines on gpiochip1:

  debian@beaglebone:~$ gpioinfo 1
  gpiochip1 - 32 lines:
	  line   0:     "P9_15B"       unused   input  active-high
	  line   1:      "P8_18"       unused   input  active-high
	  line   2:       "P8_7"        "mux"  output  active-high [used]
	  line   3:       "P8_8"        "mux"  output  active-high [used]
	  line   4:      "P8_10"        "pin"   input  active-high [used]
	  line   5:       "P8_9"        "pin"   input  active-high [used]
  <snip>
  

Test with all inputs connected to 3.3V (1I0:1I3 and 2I0:2I3)

  debian@beaglebone:~$ gpioget 4 0
  1
  debian@beaglebone:~$ gpioget 4 1
  1
  debian@beaglebone:~$ gpioget 4 2
  1
  debian@beaglebone:~$ gpioget 4 3
  1
  debian@beaglebone:~$ gpioget 5 0
  1
  debian@beaglebone:~$ gpioget 5 1
  1
  debian@beaglebone:~$ gpioget 5 2
  1
  debian@beaglebone:~$ gpioget 5 3
  1

Connect 1I0 to GND

  debian@beaglebone:~$ gpioget 4 0
  0

Connect 1I0 to 3V3

  debian@beaglebone:~$ gpioget 4 0
  1

I tried this with all the rest and got the same succesfull results.

thanks,
drew