Linux PSP GPIO Driver Guide(テキサス機器公式サイトより)-DriverMonkey
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Author:DriverMonkey
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Phone:13410905075
QQ:196568501
Linux PSP GPIO Driver Guide
Linux PSP
[hide]
1 Introduction
2 Driver Configuration
2.1 Sysfs entries configuration
3 IRQ handling
4 Driver Usage
4.1 Kernel Level
4.2 User Space - Sysfs control
5 References
Introduction
Mail:[email protected]
Phone:13410905075
QQ:196568501
Linux PSP GPIO Driver Guide
Linux PSP
Contents
[hide]
1 Introduction
2 Driver Configuration
2.1 Sysfs entries configuration
3 IRQ handling
4 Driver Usage
4.1 Kernel Level
4.2 User Space - Sysfs control
5 References
Introduction
This wiki page provides the usage information of GPIO Linux driver usage, both in user and kernel space.
Set pinmux configuration for GPIO pin usage, details of pinmux configuration are mentioned on PSP user guide. If the pinmux settings are not correct then the GPIO will not function as expected.
NOTE
Linux GPIO numbers start from "0".
NOTE
Some TI SoCs have multiple banks of GPIOs.
For example the AM335x has 4 banks of 32 GPIOs, for a total of 128 GPIO, i.e Bank-0[0..31], Bank-1[0..31], Bank-2[0..31], Bank-3[0..31]. In this case Bank-1[0..31] maps to Linux GPIO numbers 32..63, Bank-2[0..31] to Linux GPIO numbers 64..95 etc.
Driver Configuration
This section describes about the kernel configurations for GPIO driver
The default kernel configuration enables support for GPIO driver (built into the kernel).
To enable or disable GPIO driver from kernel build, follow these steps: $ make CROSS_COMPILE=arm-none-linux-gnueabi- ARCH=arm menuconfig
Select Device Drivers from the main menu. Power management options --->
[*] Networking support --->
Device Drivers --->
File systems --->
...
...
Select GPIO Support from the menu. PPS support --->
PTP clock support --->
-*- GPIO Support --->
< > Dallas's 1-wire support --->
...
...
Sysfs entries configuration
GPIO can be access using SYSFS entries from User Space. For that Select /sys/class/gpio/... (sysfs interface) from the GPIO support. [ ] Debug GPIO calls
[*] /sys/class/gpio/... (sysfs interface)
*** Memory mapped GPIO drivers: ***
< > Basic memory-mapped GPIO controllers support
...
...
After doing driver selection, exit and save the kernel configuration when prompted.
IRQ handling
GPIO pin is also used as a interrupt source, these are the general usage of IRQ handling using GPIO lines.
Map GPIO number to corresponding IRQ number, GPIO 0 need not use IRQ 0 irq_num = gpio_to_irq(30)
Request IRQ, make sure that irq_num should be non-error value request_irq(irq_num, handler, 0, "gpio_test", NULL);
Set IRQ type Raising/Falling/Level triggered set_irq_type(irq_num, IRQ_TYPE_EDGE_RISING);
During the clean-up path free the IRQ and gpio free_irq(irq_num, NULL);
gpio_free(30);
Driver Usage
Kernel Level
Allocate memory to GPIO line, can be achieved by doing gpio_request()
err = gpio_request(30, "sample_name");
Depending on the requirement set GPIO as input or output pin then set gpio value as high or low.
Setting the GPIO pin 30 as input gpio_direction_input(30);
Make pin 30 as output and set the value as high. gpio_direction_output(30, 1);
Exporting that particular pin (30) to sysfs entry then use this API gpio_export(30, true);
Get value from GPIO pin gpio_get_value(30);
User Space - Sysfs control
Enable GPIO sysfs support in kernel configuration and build the kernel Device Drivers ---> GPIO Support ---> /sys/class/gpio/... (sysfs interface)
Sysfs entries
Export the particular GPIO pin for user control. GPIO30 is taken as example. $ echo 30 > /sys/class/gpio/export
Change the GPIO pin direction to in/out $ echo "out" > /sys/class/gpio/gpio30/direction
or $ echo "in" > /sys/class/gpio/gpio30/direction
Change the value $ echo 1 > /sys/class/gpio/gpio30/value
or $ echo 0 > /sys/class/gpio/gpio30/value
Unexport the GPIO pin $ echo 30 > /sys/class/gpio/unexport
Note: GPIO's which are used already in the drivers can not be control from sysfs, unless until driver export that particular pin.
Run these commands for knowing what are the GPIO's already requested in the drivers. $ mount -t debugfs debugfs /sys/kernel/debug
$ cat /sys/kernel/debug/gpio
This section describes about the kernel configurations for GPIO driver
The default kernel configuration enables support for GPIO driver (built into the kernel).
To enable or disable GPIO driver from kernel build, follow these steps:
$ make CROSS_COMPILE=arm-none-linux-gnueabi- ARCH=arm menuconfig
Select Device Drivers from the main menu.
Power management options --->
[*] Networking support --->
Device Drivers --->
File systems --->
...
...
Select GPIO Support from the menu.
PPS support --->
PTP clock support --->
-*- GPIO Support --->
< > Dallas's 1-wire support --->
...
...
Sysfs entries configuration
GPIO can be access using SYSFS entries from User Space. For that Select /sys/class/gpio/... (sysfs interface) from the GPIO support.
[ ] Debug GPIO calls
[*] /sys/class/gpio/... (sysfs interface)
*** Memory mapped GPIO drivers: ***
< > Basic memory-mapped GPIO controllers support
...
...
After doing driver selection, exit and save the kernel configuration when prompted.
IRQ handling
GPIO pin is also used as a interrupt source, these are the general usage of IRQ handling using GPIO lines.
Map GPIO number to corresponding IRQ number, GPIO 0 need not use IRQ 0 irq_num = gpio_to_irq(30)
Request IRQ, make sure that irq_num should be non-error value request_irq(irq_num, handler, 0, "gpio_test", NULL);
Set IRQ type Raising/Falling/Level triggered set_irq_type(irq_num, IRQ_TYPE_EDGE_RISING);
During the clean-up path free the IRQ and gpio free_irq(irq_num, NULL);
gpio_free(30);
Driver Usage
Kernel Level
Allocate memory to GPIO line, can be achieved by doing gpio_request()
err = gpio_request(30, "sample_name");
Depending on the requirement set GPIO as input or output pin then set gpio value as high or low.
Setting the GPIO pin 30 as input gpio_direction_input(30);
Make pin 30 as output and set the value as high. gpio_direction_output(30, 1);
Exporting that particular pin (30) to sysfs entry then use this API gpio_export(30, true);
Get value from GPIO pin gpio_get_value(30);
User Space - Sysfs control
Enable GPIO sysfs support in kernel configuration and build the kernel Device Drivers ---> GPIO Support ---> /sys/class/gpio/... (sysfs interface)
Sysfs entries
Export the particular GPIO pin for user control. GPIO30 is taken as example. $ echo 30 > /sys/class/gpio/export
Change the GPIO pin direction to in/out $ echo "out" > /sys/class/gpio/gpio30/direction
or $ echo "in" > /sys/class/gpio/gpio30/direction
Change the value $ echo 1 > /sys/class/gpio/gpio30/value
or $ echo 0 > /sys/class/gpio/gpio30/value
Unexport the GPIO pin $ echo 30 > /sys/class/gpio/unexport
Note: GPIO's which are used already in the drivers can not be control from sysfs, unless until driver export that particular pin.
Run these commands for knowing what are the GPIO's already requested in the drivers. $ mount -t debugfs debugfs /sys/kernel/debug
$ cat /sys/kernel/debug/gpio
irq_num = gpio_to_irq(30)
request_irq(irq_num, handler, 0, "gpio_test", NULL);
set_irq_type(irq_num, IRQ_TYPE_EDGE_RISING);
free_irq(irq_num, NULL);
gpio_free(30);
Kernel Level
Allocate memory to GPIO line, can be achieved by doing
gpio_request()
err = gpio_request(30, "sample_name");
Depending on the requirement set GPIO as input or output pin then set gpio value as high or low.
Setting the GPIO pin 30 as input
gpio_direction_input(30);
Make pin 30 as output and set the value as high.
gpio_direction_output(30, 1);
Exporting that particular pin (30) to sysfs entry then use this API
gpio_export(30, true);
Get value from GPIO pin
gpio_get_value(30);
User Space - Sysfs control
Enable GPIO sysfs support in kernel configuration and build the kernel
Device Drivers ---> GPIO Support ---> /sys/class/gpio/... (sysfs interface)
Sysfs entries
Export the particular GPIO pin for user control. GPIO30 is taken as example.
$ echo 30 > /sys/class/gpio/export
Change the GPIO pin direction to in/out
$ echo "out" > /sys/class/gpio/gpio30/direction
or
$ echo "in" > /sys/class/gpio/gpio30/direction
Change the value
$ echo 1 > /sys/class/gpio/gpio30/value
or
$ echo 0 > /sys/class/gpio/gpio30/value
Unexport the GPIO pin
$ echo 30 > /sys/class/gpio/unexport
Note: GPIO's which are used already in the drivers can not be control from sysfs, unless until driver export that particular pin.
Run these commands for knowing what are the GPIO's already requested in the drivers.
$ mount -t debugfs debugfs /sys/kernel/debug
$ cat /sys/kernel/debug/gpio