Difference between revisions of "EBC Exercise 51 GPIO aggregator"
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0 --w------- 1 root root 4096 Jul 29 10:56 uevent | 0 --w------- 1 root root 4096 Jul 29 10:56 uevent | ||
0 --w------- 1 root root 4096 Jul 29 10:57 unbind | 0 --w------- 1 root root 4096 Jul 29 10:57 unbind | ||
| − | bone$ '''sudo chgrp | + | bone$ '''sudo chgrp gpio *''' |
bone$ '''sudo chmod g+w *''' | bone$ '''sudo chmod g+w *''' | ||
bone$ '''ls -ls''' | bone$ '''ls -ls''' | ||
total 0 | total 0 | ||
| − | 0 --w--w---- 1 root | + | 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 bind |
| − | 0 --w--w---- 1 root | + | 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 delete_device |
| − | 0 lrwxrwxrwx 1 root root | + | 0 lrwxrwxrwx 1 root root 0 Jul 29 10:57 module -> ../../../../module/gpio_aggregator |
| − | 0 --w--w---- 1 root | + | 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 new_device |
| − | 0 --w--w---- 1 root | + | 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 uevent |
| − | 0 --w--w---- 1 root | + | 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 unbind |
bone$ '''gpiodetect''' | bone$ '''gpiodetect''' | ||
gpiochip0 [gpio-0-31] (32 lines) | gpiochip0 [gpio-0-31] (32 lines) | ||
| Line 40: | Line 40: | ||
gpiochip2 [gpio-64-95] (32 lines) | gpiochip2 [gpio-64-95] (32 lines) | ||
gpiochip3 [gpio-96-127] (32 lines) | gpiochip3 [gpio-96-127] (32 lines) | ||
| − | bone$ ''' | + | |
| + | == Map pins == | ||
| + | Let's map P9_14, P9_16, P9_18 and P9_22 to lines 0-3 on a new gpiochip. | ||
| + | |||
| + | bone$ '''gpioinfo | grep -e chip -e P9_1[468] -e P9_22''' | ||
| + | gpiochip0 - 32 lines: | ||
| + | line 2: "P9_22 [spi0_sclk]" "gpio-aggregator.0" input active-high [used] | ||
| + | line 4: "P9_18 [spi0_d1]" "gpio-aggregator.0" output active-high [used] | ||
| + | gpiochip1 - 32 lines: | ||
| + | line 18: "P9_14 [ehrpwm1a]" "gpio-aggregator.0" output active-high [used] | ||
| + | line 19: "P9_16 [ehrpwm1b]" "gpio-aggregator.0" input active-high [used] | ||
| + | gpiochip2 - 32 lines: | ||
| + | gpiochip3 - 32 lines: | ||
| + | {| class="wikitable" | ||
| + | |- | ||
| + | ! Header !! gpiochip || line | ||
| + | |- | ||
| + | | P9_14 || 1 || 18 | ||
| + | |- | ||
| + | | P9_16 || 1 || 19 | ||
| + | |- | ||
| + | | P9_18 || 0 || 4 | ||
| + | |- | ||
| + | | P9_22 || 0 || 2 | ||
| + | |} | ||
| + | bone$ '''echo "gpio-32-63 18,19 gpio-0-31 4,2" > new_device''' | ||
bone$ '''ls''' | bone$ '''ls''' | ||
bind delete_device gpio-aggregator.0 module new_device uevent unbind | bind delete_device gpio-aggregator.0 module new_device uevent unbind | ||
| Line 46: | Line 71: | ||
driver driver_override gpio gpiochip4 modalias power subsystem uevent | driver driver_override gpio gpiochip4 modalias power subsystem uevent | ||
bone$ '''gpioinfo | tail -6''' | bone$ '''gpioinfo | tail -6''' | ||
| − | |||
line 31: "NC" unused input active-high | line 31: "NC" unused input active-high | ||
| − | gpiochip4 - | + | gpiochip4 - 4 lines: |
| − | line 0: unnamed unused | + | line 0: unnamed unused output active-high |
line 1: unnamed unused input active-high | line 1: unnamed unused input active-high | ||
| − | line 2: unnamed unused input active-high | + | line 2: unnamed unused input active-high |
| + | line 3: unnamed unused output active-high | ||
| + | |||
| + | bone$ '''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 [gpio-aggregator.0] (4 lines) | ||
| + | There's a new gpiochip, '''gpiochip4''' | ||
| + | |||
| + | == Test it == | ||
| + | The new mappings are: | ||
| + | {| class="wikitable" | ||
| + | |- | ||
| + | ! Header !! gpiochip || line | ||
| + | |- | ||
| + | | P9_14 || 4 || 0 | ||
| + | |- | ||
| + | | P9_16 || 4 || 1 | ||
| + | |- | ||
| + | | P9_18 || 4 || 2 | ||
| + | |- | ||
| + | | P9_22 || 4 || 3 | ||
| + | |} | ||
| + | |||
| + | Turn them all on, then off. Since they are all now on the same chip, one command can be used. | ||
| + | bone$ '''gpioset gpiochip4 0=1 1=1 2=1 3=1''' | ||
| + | bone$ '''gpioset gpiochip4 0=0 1=0 2=0 3=0''' | ||
| + | |||
| + | It's interesting the LEDs stay on, even after the command exits. Normally gpioset returns to it's original state. | ||
| + | |||
| + | == Delete it == | ||
| + | bone$ '''echo gpio-aggregator.0 > delete_device ''' | ||
{{YoderFoot}} | {{YoderFoot}} | ||
Latest revision as of 11:03, 29 July 2022
Embedded Linux Class by Mark A. Yoder
Here are some quick notes on the GPIO aggregator which allows one to group a number of GPIOs into a virtual GPIO chip, visible as an additional /dev/gpiochip*. Its documentation can be found in Documentation/admin-guide/gpio/gpio-aggregator.rst.
My info comes from:
https://bootlin.com/blog/gpio-aggregator-a-virtual-gpio-chip/
https://elixir.bootlin.com/linux/v5.12/source/Documentation/admin-guide/gpio/gpio-aggregator.rst
https://elinux.org/images/c/cb/Linux_GPIO-Evolution_and_Current_State_of_the_User_API.pdf
Contents
Install
bone$ grep -i gpio_agg /boot/config-5.10.120-ti-r48 CONFIG_GPIO_AGGREGATOR=m bone$ sudo modprobe gpio-aggregator bone$ cd /sys/bus/platform/drivers/gpio-aggregator bone$ ls -ls total 0 0 --w------- 1 root root 4096 Jul 29 10:57 bind 0 --w------- 1 root root 4096 Jul 29 10:57 delete_device 0 lrwxrwxrwx 1 root root 0 Jul 29 10:57 module -> ../../../../module/gpio_aggregator 0 --w------- 1 root root 4096 Jul 29 10:57 new_device 0 --w------- 1 root root 4096 Jul 29 10:56 uevent 0 --w------- 1 root root 4096 Jul 29 10:57 unbind bone$ sudo chgrp gpio * bone$ sudo chmod g+w * bone$ ls -ls total 0 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 bind 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 delete_device 0 lrwxrwxrwx 1 root root 0 Jul 29 10:57 module -> ../../../../module/gpio_aggregator 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 new_device 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 uevent 0 --w--w---- 1 root gpio 4096 Jul 29 11:09 unbind bone$ 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)
Map pins
Let's map P9_14, P9_16, P9_18 and P9_22 to lines 0-3 on a new gpiochip.
bone$ gpioinfo | grep -e chip -e P9_1[468] -e P9_22 gpiochip0 - 32 lines: line 2: "P9_22 [spi0_sclk]" "gpio-aggregator.0" input active-high [used] line 4: "P9_18 [spi0_d1]" "gpio-aggregator.0" output active-high [used] gpiochip1 - 32 lines: line 18: "P9_14 [ehrpwm1a]" "gpio-aggregator.0" output active-high [used] line 19: "P9_16 [ehrpwm1b]" "gpio-aggregator.0" input active-high [used] gpiochip2 - 32 lines: gpiochip3 - 32 lines:
| Header | gpiochip | line |
|---|---|---|
| P9_14 | 1 | 18 |
| P9_16 | 1 | 19 |
| P9_18 | 0 | 4 |
| P9_22 | 0 | 2 |
bone$ echo "gpio-32-63 18,19 gpio-0-31 4,2" > new_device bone$ ls bind delete_device gpio-aggregator.0 module new_device uevent unbind bone$ ls gpio-aggregator.0 driver driver_override gpio gpiochip4 modalias power subsystem uevent bone$ gpioinfo | tail -6 line 31: "NC" unused input active-high gpiochip4 - 4 lines: line 0: unnamed unused output active-high line 1: unnamed unused input active-high line 2: unnamed unused input active-high line 3: unnamed unused output active-high
bone$ 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 [gpio-aggregator.0] (4 lines)
There's a new gpiochip, gpiochip4
Test it
The new mappings are:
| Header | gpiochip | line |
|---|---|---|
| P9_14 | 4 | 0 |
| P9_16 | 4 | 1 |
| P9_18 | 4 | 2 |
| P9_22 | 4 | 3 |
Turn them all on, then off. Since they are all now on the same chip, one command can be used.
bone$ gpioset gpiochip4 0=1 1=1 2=1 3=1 bone$ gpioset gpiochip4 0=0 1=0 2=0 3=0
It's interesting the LEDs stay on, even after the command exits. Normally gpioset returns to it's original state.
Delete it
bone$ echo gpio-aggregator.0 > delete_device
Embedded Linux Class by Mark A. Yoder
