GPIO User Guide

REVISION HISTORY

Revision No.	Description	Date
1.0	Initial release	04/18/2023
1.1	Add Chapter VIII DEBUG&FAQ	04/08/2025

1. Overview¶

General Purpose Input/Output is referred to as GPIO. The GPIO module is implemented using standard LINUX architecture and is therefore operable via standard GPIO interface.

1-1 GPIO Framework

As illustrated in the GPIO framework above, the layer in the middle is gpiolib, for managing the GPIOs in the system. The gpiolib is a collection of the general GPIO operations. Depending on the characteristics of the GPIO, the gpiolib interfaces to a corresponding uniform software interface provided by other drivers for operating the GPIO. On the downward side, the gpiolib provides a set of frameworks to operate different chips. For different chips, you need only to implement drv_gpio_io.c and then use the registration function provided by gpiolib to mount it to the gpiolib.

2. Keyword¶

2.1. GPIO Index¶

To use the HW checklist, find the GPIO Index corresponding to the pad name of the GPIO in the schematics. The GPIO Index serves as the input parameter for software to operate the associated GPIO function.

For example, if PAD_KEY1 is the GPIO intended to be used, you should look up Table 1 to find the GPIO Index corresponding to this pad, which is 12 in this case.

Table 1: Mapping between GPIO Index and PAD

Pad Name	GPIO Index	Pad Name	GPIO Index	Pad Name	GPIO Index
PAD_UART0_TX	0	PAD_PWM_OUT00	1	PAD_PWM_OUT01	2
PAD_SPI_CK	3	PAD_SPI_HLD	4	PAD_SPI_CZ	5
PAD_SPI_WPZ	6	PAD_SPI_DI	7	PAD_SPI_DO	8
PAD_GPIOE_00	9	PAD_GPIOE_01	10	PAD_GPIOE_02	11
PAD_GPIOE_03	12	PAD_GPIOE_04	13	PAD_GPIOE_05	14
PAD_GPIOE_06	15	PAD_GPIOE_07	16	PAD_GPIOE_08	17
PAD_GPIOE_09	18	PAD_GPIOE_10	19	PAD_GPIOE_11	20
PAD_GPIOE_12	21	PAD_GPIOE_13	22	PAD_GPIOE_14	23
PAD_GPIOE_15	24	PAD_GPIOE_16	25	PAD_GPIOE_17	26
PAD_GPIOE_18	27	PAD_GPIOE_19	28	PAD_GPIOE_20	29
PAD_GPIOE_21	30	PAD_GPIOE_22	31	PAD_GPIOE_23	32
PAD_GPIOE_24	33	PAD_GPIOE_25	34	PAD_GPIOE_26	35
PAD_GPIOE_27	36	PAD_GPIOE_28	37	PAD_GPIOA_00	38
PAD_GPIOA_01	39	PAD_GPIOA_02	40	PAD_GPIOA_03	41
PAD_GPIOA_04	42	PAD_GPIOA_05	43	PAD_GPIOA_06	44
PAD_GPIOA_07	45	PAD_GPIOA_08	46	PAD_GPIOA_09	47
PAD_GPIOA_10	48	PAD_GPIOA_11	49	PAD_EMMC_RST	50
PAD_EMMC_CLK	51	PAD_EMMC_CMD	52	PAD_EMMC_DS	53
PAD_EMMC_D3	54	PAD_EMMC_D4	55	PAD_EMMC_D0	56
PAD_EMMC_D5	57	PAD_EMMC_D1	58	PAD_EMMC_D6	59
PAD_EMMC_D2	60	PAD_EMMC_D7	61	PAD_GPIOA_12	62
PAD_GPIOA_13	63	PAD_GPIOA_14	64	PAD_GPIOA_15	65
PAD_GPIOA_16	66	PAD_GPIOA_17	67	PAD_GPIOA_18	68
PAD_GPIOA_19	69	PAD_GPIOB_00	70	PAD_GPIOB_01	71
PAD_GPIOB_02	72	PAD_GPIOB_03	73	PAD_GPIOB_04	74
PAD_GPIOB_05	75	PAD_GPIOB_06	76	PAD_GPIOB_07	77
PAD_GPIOB_08	78	PAD_OUTP_RX0_CH0	79	PAD_OUTN_RX0_CH0	80
PAD_OUTP_RX0_CH1	81	PAD_OUTN_RX0_CH1	82	PAD_OUTP_RX0_CH2	83
PAD_OUTN_RX0_CH2	84	PAD_OUTP_RX0_CH3	85	PAD_OUTN_RX0_CH3	86
PAD_GPIOC_00	87	PAD_GPIOC_01	88	PAD_GPIOC_02	89
PAD_GPIOC_03	90	PAD_GPIOC_04	91	PAD_GPIOC_05	92
PAD_GPIOC_06	93	PAD_GPIOC_07	94	PAD_GPIOC_08	95
PAD_OUTP_CH0	96	PAD_OUTN_CH0	97	PAD_OUTP_CH1	98
PAD_OUTN_CH1	99	PAD_OUTP_CH2	100	PAD_OUTN_CH2	101
PAD_OUTP_CH3	102	PAD_OUTN_CH3	103	PAD_OUTP_CH4	104
PAD_OUTN_CH4	105	PAD_SAR_ADC0_00	106	PAD_SAR_ADC0_01	107
PAD_SAR_ADC0_02	108	PAD_SAR_ADC0_03	109	PAD_SAR_ADC0_04	110
PAD_SAR_ADC0_05	111	PAD_SAR_ADC0_06	112	PAD_SAR_ADC0_07	113
PAD_SAR_ADC0_08	114	PAD_SAR_ADC0_09	115	PAD_SAR_ADC0_10	116
PAD_SAR_ADC0_11	117	PAD_SAR_ADC0_12	118	PAD_SAR_ADC0_13	119
PAD_SAR_ADC0_14	120	PAD_PWM_ADC01	121	PAD_PWM_ADC00	122
PAD_GPIOD_01	123	PAD_GPIOD_02	124	PAD_GPIOD_03	125
PAD_GPIOD_00	126	PAD_UART0_RX	127	PAD_PM_GPIO4	128
PAD_PM_GPIO5	129	PAD_PM_PWM1_OUT	130	PAD_PM_I2C_SDA	131
PAD_PM_PWM0_OUT	132	PAD_PM_I2C_SCL	133	PAD_PM_GPIO1	134
PAD_PM_GPIO3	135	PAD_PM_UART1_TX	136	PAD_PM_GPIO2	137
PAD_PM_GPIO7	138	PAD_PM_GPIO6	139	PAD_PM_UART1_RX	140
PAD_PM_ADC00_IN	141	PAD_PM_GPIO0	142	PAD_PM_SAR_GPIO0	143
PAD_PM_SAR_GPIO1	144	PAD_PM_SAR_GPIO2	145	PAD_PM_SAR_GPIO3	146
PAD_PM_SAR_GPIO4	147

3. Function Description¶

There are 148 GPIO pins with numbers 0-147, all of which can be configured as GPIO Mode
Support configuring the up and down states of gpio pins
Support configuring the driver capability of gpio pins

4. Hardware Connection¶

Connect the corresponding gpio pin to the hardware.

5. Uboot Usage¶

5.1. Uboot Config¶

[*] SigmaStar drivers  --->

    [*]   SigmaStar GPIO
    [*]   SigmaStar padmux

drivers/sstar/gpio/drv_gpio.c
drivers/sstar/gpio/drv_gpio.h
drivers/sstar/gpio/pcupid/hal_gpio.c
drivers/sstar/gpio/pcupid/hal_gpio.h
drivers/sstar/gpio/pcupid/hal_pinmux.c
drivers/sstar/gpio/pcupid/hal_pinmux.h
drivers/sstar/include/pcupid/gpio.h
drivers/sstar/include/pcupidpadmux.h

5.3. DTS Parameter Configuration¶

gpio: gpio {
    compatible = "sstar,gpio";
    status = "okay";
};

Attribute	Description	Note
compatible	Used to match the driver for driver registration	Modification not allowed
status	Driver switch	okay/disabled; can be modified where necessary

5.4. Uboot Command Parameter¶

<input|set|clear|toggle> <pin> → input/set/clear/toggle the specified pin

gpio status [-a] [<bank> | <pin>] → show [all / claimed] GPIOs

Command	Parameter	Description
input	pin	Set the pin with the specified pin number as GPIO input mode
set	pin	Set the pin with the specified pin number as GPIO output high mode
clear	pin	Set the pin with the specified pin number as GPIO output low mode
toggle	pin	Toggle the level of the pin with the specified pin number
status	pin	Check the status of the pin with the specified pin number

5.5. Uboot Command Usage Example¶

gpio input <gpio#> → gpio input 69 // gpio69 set as input

gpio set <gpio#> → gpio set 10 // gpio10 set as output high

gpio clear <gpio#> → gpio clear 49 // gpio49 set as output low

gpio toggle <gpio#> → gpio toggle 49 // gpio49 level toggle

gpio status <gpio#> → gpio status 20 // gpio20 status

5.6. Pin initial state setting¶

5.6.1. Uboot Config¶

When compiling Uboot: make menuconfig

[*] SigmaStar drivers  --->

    [*]   SigmaStar PAD_INIT

5.6.2. Function usage instructions¶

The initial state of the PAD includes input/output state, level state, internal pull-up state, and pin drive capability level. Therefore, when setting the initial state of the PAD, the above four states are mainly configured. The specific configuration format in xxx-padmux.dtsi is as follows:

/*
    * Format:
    * <Pad_Index   Direction       Level_State        Pull_State          Driving_Level>
    */
1. <PAD_OUTP_RX0_CH0 GPIO_DIR_IN    GPIO_LEVEL_NA     PAD_PULL_UP         PAD_DRV_1>,
2. <PAD_PM_I2C_SDA   GPIO_DIR_OUT   GPIO_LEVEL_HIGH   PAD_PULL_DOWN       PAD_DRV_1>,
3. <PAD_GPIOC_00     GPIO_DIR_NA    GPIO_LEVEL_NA     PAD_HIZ             PAD_DRV_3>,
4. <GPIO_NR     GPIO_DIR_NA     GPIO_LEVEL_NA      PAD_PULL_DEFAULT    PAD_DRV_DEFAULT>;

As shown above:

Pad_Index: Indicates the PAD number, refer to Table 1-1: GPIO NUM and PAD correspondence table.
Direction: Indicates the input/output mode of the Pad, which can be configured as: GPIO_DIR_IN, GPIO_DIR_OUT, GPIO_DIR_NA.

GPIO_DIR_IN means setting as input, and GPIO_DIR_OUT means setting as output. If you only need to set the internal pull-up state and driving capability level of the PAD, and do not need to set the PAD to GPIO mode, you can pass GPIO_DIR_NA in the Direction position. When the Pad is set to input/output mode, you need to set this Pad to GPIO mode, so you need to add the GPIO mode setting to the padmux configuration position
```
1.    <PAD_OUTP_RX0_CH0      PINMUX_FOR_GPIO_MODE      MDRV_PUSE_GPIO_OUTP_RX0_CH0>,
2.    <PAD_PM_I2C_SDA        PINMUX_FOR_GPIO_MODE      MDRV_PUSE_GPIO_PM_I2C_SDA>,
3.    <PAD_GPIOC_00          PINMUX_FOR_GPIO_MODE      MDRV_PUSE_GPIO_GPIOC_00>,
```
Level_State: Indicates the level high and low state, which can be configured as: GPIO_LEVEL_HIGH, GPIO_LEVEL_LOW, GPIO_LEVEL_NA.

GPIO_LEVEL_HIGH indicates high level, GPIO_LEVEL_LOW indicates low level, and GPIO_LEVEL_NA indicates that the initial level does not need to be configured, and the default level can be used.
Pull_State: Indicates the internal pull-up and pull-down state, which can be configured as: PAD_PULL_UP, PAD_PULL_DOWN, PAD_HIZ, PAD_PULL_DEFAULT.

PAD_PULL_UP indicates internal pull-up, PAD_PULL_DOWN indicates internal pull-down, and PAD_HIZ indicates floating. When you do not need to set the internal pull-up state, you can select PAD_PULL_DEFAULT to set it to the default state.

Driving_Level: Indicates the driving capability level, which can be configured as PAD_DRV_0, PAD_DRV_1, PAD_DRV_2... When you do not need to set the driving capability level, you can also select PAD_DRV_DEFAULT, that is, use the current driving capability level without configuration.

Name	Config
Direction	GPIO_DIR_IN, GPIO_DIR_OUT, GPIO_DIR_NA
Level_State	GPIO_LEVEL_HIGH, GPIO_LEVEL_LOW, GPIO_LEVEL_NA
Pull_State	PAD_PULL_UP, PAD_PULL_DOWN, PAD_HIZ, PAD_PULL_DEFAULT
Driving_Level	PAD_DRV_0, PAD_DRV_1, PAD_DRV_2......PAD_DRV_DEFAULT

6. Kernel Usage¶

6.1. Kernel Config¶

Device Drivers  --->

    [*] GPIO Support  --->
        [*]   /sys/class/gpio/... (sysfs interface)

    [*] SStar SoC platform drivers  --->
        [*]   GPIO driver
        [*]   PADMUX driver

drivers/sstar/gpio/drv_gpio.c
drivers/sstar/gpio/drv_gpio_io.c
drivers/sstar/gpio/pcupid/hal_gpio.c
drivers/sstar/gpio/pcupid/hal_gpio.h
drivers/sstar/gpio/pcupid/hal_pinmux.c
drivers/sstar/gpio/pcupid/hal_pinmux.h
drivers/sstar/gpio/os/gpio_os.h
drivers/sstar/gpio/ut/gpio_irq_test.c
drivers/sstar/include/pcupid/gpio.h
drivers/sstar/include/pcupid/padmux.h

6.3. DTS Parameter Configuration¶

gpio: gpio {
    compatible = "sstar,gpio";
    #gpio-cells = <2>;
    status = "okay";
};

Attribute	Description	Note
compatible	Used to match the driver for driver registration	Modification not allowed
#gpio-cells	Used to declare the number of device node GPIO cells	If set to 2, the first cell represents the GPIO number and the second cell represents the effective level of the GPIO
status	Driver switch	ok/disabled; can be modified where necessary

6.4. Module Usage Introduction¶

6.4.1. The export/unexport File Interface¶

The user space can operate the GPIO through sysfs interface.

The source code corresponding to /sys/class/gpio is located at driver/gpio/gpiolib-sysfs.c.

There are three files under the /sys/class/gpio directory, i.e. export/unexport, gpioN and gpio_chipN, as listed in the table below:

Filename	Access Permission	Value	Description
export	wo	GPIO Index	Request control of a GPIO in user space
unexport	wo	GPIO Index	Remove control of a GPIO in user space
gpioN	ro		Information on a specific GPIO including direction, value, etc.
gpio_chipN	ro		The GPIO controller

The /sys/class/gpio/export file is write-only and non-readable. The user program may write a specific GPIO index to kernel to request exportation of access right of a certain GPIO to user space (sysfs), provided that no application for exportation of access right against this GPIO interface is under processing by the kernel. Take GPIO index 12 as an example. You should enter the command:
```
# echo 12 > export
```
By this command, a node gpio12 will be created for the GPIO with Index 12, and a gpio12 directory will be created under /sys/class/gpio, as shown below:
The /sys/class/gpio/unexport file is likewise write-only and non-readable. Contrary to the export function, the unexport command allows you to remove the user space (sysfs) interface by writing the GPIO index. To remove gpio12 file directory, for example, enter the following command:
```
# echo 12 > unexport
```
By this command, the gpio12 node will be removed, as illustrated below:

6.4.2. /sys/class/gpio/gpioN¶

/sys/class/gpio/gpioN refers to a specific GPIO port, wherein the following attribute files are included:

Filename	Access Permission	Value	Description
direction	rw	in	Input mode, value is non-writable
		out	Output mode, value is writable
		high	Output state, high level by default, value is writable
		low	Output state, low level by default, value is writable
value	rw	1	High level state
value	rw	0	Low level state
edge	rw	none	Disable gpio interrupt
		rising	Enable gpio interrupt, and set gpio as rising edge trigger
		falling	Enable gpio interrupt, and set gpio as falling edge trigger
		both	Enable gpio interrupt, and set gpio as both edge trigger

direction, which indicates the direction of the GPIO port, that is, whether the read result is in or out. The read command is:

# cat direciton

value, which represents the level of the GPIO pin. 0 means low level, and 1 high level. The read command is:

# cat value

You can do write operation against the direction, using the command below:

# echo in > direction

# echo out > direction

If the direction is configured as out, the level will be low by default and the value will be writable by the following command:

# echo 1 > value

# echo 0 > value

When writing low or high to the direction, you can set the GPIO as output and configure the output level at the same time. The command to this effect is:

# echo high > direction

# echo low > direction

Of course, this attribute will not exist if it is not supported by the kernel or not allowed by the kernel code. For example, if the kernel calls gpio_export(N,0), it means that the kernel does not want to modify the direction attribute of the GPIO port.

edge, which means whether to enable gpio interrupt, and set trigger mode, supporting rising edge trigger, falling edge trigger and both edge trigger:

# cat edge

The write operation command to edge is:

# echo none > edge
# echo rising > edge
# echo falling > edge
# echo both > edge

If you need to enable a pin's interrupt, please set the pin as input status and set the trigger mode, then the poll(2) function can be called to monitor the interrupt, and the poll(2) function will return once the interrupt is triggered.

6.4.3. /sys/class/sstar/msys¶

The original LINUX GPIO framework currently does not support GPIO pull-up/pull-down and driving strength configuration. So, based on the standard LINUX GPIO framework, we have added an additional file interface for adjusting the pull-up/pull-down and driving strength of the GPIO. To support this function, open the CONFIG_MSYS_GPIO configuration in menuconfig: Device Drivers -> SStar SoC platform drivers -> msys api ->support GPIO pull and driving modify

The source code corresponding to /sys/class/sstar/msys is located at driver/sstar/msys/ms_msys.c.

Be sure to set the GPIO as input state before setting the pull-up/pull-down configuration, because the pull-up/pull-down resistor value cannot be measured when the GPIO is in output state:

After setting the pin as input state, enter the file directory sys/class/sstar/msys:

gpio_pull, which can be configured as up or down

Filename Access Permission Value Description

gpio_pull rw up Pull-up Mode

down Pull-down Mode

To check whether the pull state of the GPIO is currently pull-up, pull-down or pull-off:
```
1. # echo 50 > gpio_pull
2. # cat gpio_pull
```
If the input GPIO Index or GPIO Name is illegal, an error will be returned:

The command to set the GPIO pull state is:
```
1. # echo 50 up > gpio_pull
2. # echo 50 down > gpio_pull
```
You can check the GPIO pull state after completing the setting, using the command below, wherein 50 represents the GPIO Index and PAD_OUTN_RX0_CH3 represents the GPIO Name.
```
1. # cat gpio_pull
```
If the input GPIO Index or GPIO Name is illegal, an error will be returned:

To check whether a specific bit has been correctly written, look up the HW checklist to find the corresponding PAD (for example GPIO INDEX: 50 below). When pulled up, the PE bit will be 1 and the PS bit will be 0; when pulled down, the PE bit will be 1 and the PS bit will be 0. The command to this effect is:
```
1. # riu_r 0x103e 0x34
```
To check Bit 6 and Bit 11 of riu_r return value:
gpio_drive, which can set the level of the driving strength

Filename Access Permission Value Description

gpio_drive rw 0~8 Set the level of the GPIO driving strength

The level of GPIO driving strength can be checked using the HW checklist.

To check the command bit of the initial driving strength of the GPIO (you can directly use the Pad Name of GPIO43, PAD_OUTP_RX0_CH0 too):
```
1. # echo 43 > gpio_drive
2. # cat gpio_drive
```
If the input GPIO Index or GPIO Name is illegal, an error will be returned:

Before configuring the driving strength, set the GPIO in high-level output state for purpose of measurement. The command to this effect is:
```
1. # echo 43 1 > gpio_drive
```
wherein, 43 refers to the GPIO Index and 1 refers to the level of the driving strength, which corresponds to 4mA.

After setting the driving strength, check the state of the gpio_driver using the command set forth below. As illustrated, the driving strength of the pin with GPIO Index 43 has been set to 4mA successfully.
```
1. # cat gpio_drive
```
To check whether a specific bit has been corrected written, look up the HW checklist to find the corresponding PAD (for example GPIO INDEX: 50 below). When the level of the driving strength is 1, [103E56]#7 ~ #8 will be 01. The command to this effect is:
```
1. # riu_r 0x103e 0x2B
```
To check Bit 7 and Bit 8 of riu_r return value:

6.4.4. Usage of Multiplexing Function¶

When you want to use the multiplexing function of GPIO, you need first to obtain the name of the pin to be operated and the Tmux Mode to be multiplexed, and then configure them in xxx-padmux.dtsi:

<PAD_EMMC_RST            PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_RST>,
<PAD_EMMC_CLK            PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_CLK>,
<PAD_EMMC_CMD            PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_CMD>,
<PAD_EMMC_D0             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D0>,
<PAD_EMMC_D1             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D1>,
<PAD_EMMC_D2             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D2>,
<PAD_EMMC_D3             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D3>,
<PAD_EMMC_D4             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D4>,
<PAD_EMMC_D5             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D5>,
<PAD_EMMC_D6             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D6>,
<PAD_EMMC_D7             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_D7>,
<PAD_EMMC_DS             PINMUX_FOR_EMMC8B_BOOT_MODE_1    MDRV_PUSE_EMMC_DS>,

As shown above, the first column and the second column represent Pad Name and Tmux Mode respectively, wherein MDRV_PUSE_XXX can be understood as the name of the current configuration of this group.

Note that there are some things to pay attention to when configuring the multiplexing function:

Each pad can only be configured with one mode; it is not allowed to configure one pad with multiple modes at the same time.
Each pulse can only correspond to one set of configuration; otherwise, conflicts will occur.
The Pad and Mode configured must match.
It is not allowed to perform multiplexing operations directly in the driver; the multiplexing configurations should be incorporated into xxx_padmux.dtsi collectively (except those requiring dynamical adjustment of the multiplexing configuration), to facilitate management and reduce configuration conflicts.

6.4.5. Pin initial state setting¶

When compiling the kernel: make menuconfig

Device Drivers-->
    [*] SStar SoC platform drivers-->
        [*] PAD_INIT driver

For details, please refer to this article section: Function usage instructions

6.5. Sample Code¶

6.5.1 User space interruption¶

For user space code to enable GPIO interrupt, please refer to sstargpio_poll.c.

1.    #include <stdio.h>
2.    #include <stdlib.h>
3.    #include <unistd.h>
4.    #include <fcntl.h>
5.    #include <sys/poll.h>
6.
7.    int main(int argc, char *argv[])
8.    {
9.        char buff[1024];
10.        int gpio_id;
12.        struct pollfd fds[1];
13.        int gpio_fd = open("/sys/class/gpio/gpio135/value", O_RDONLY);
14.        if (gpio_fd == -1)
15.            {printf("gpio open\n");}
16.        else
17.            {printf("/sys/class/gpio/gpio135/value\n");}
18.        fds[0].fd = gpio_fd;
19.        fds[0].events = POLLPRI;
20.        int ret = read(gpio_fd, buff, 10);
21.        if (ret == -1)
22.            printf("read fail\n");
23.        else
24.            printf("read\n");
25.        while (1)
26.        {
27.            printf("revents is %d\n", fds[0].revents);
28.            ret = poll(fds, 1, -1);
29.            if (ret == -1)
30.                printf("poll\n");
31.
32.            if (fds[0].revents & POLLPRI)
33.            {
34.                ret = lseek(gpio_fd, 0, SEEK_SET);
35.                if (ret == -1)
36.                    printf("lseek\n");
37.                ret = read(gpio_fd, buff, 10);
38.                if (ret == -1)
39.                    printf("read\n");
40.                printf("get interrupt\n");
41.            }
42.        }
43.    }

6.5.2 API USE Reference¶

#include <drv_gpio.h>

int main()
{
    u8 index = 0;
    gpio_request(index,"test");
    gpio_direction_input(index);

    //do your operation
    gpio_set_value(index,1);

    //.....

    gpio_free(index);
}

7. API Reference¶

This module provides the following interfaces：

API Name	Function
gpio_request	Create a GPIO port.
gpio_free	Free a GPIO port.
gpio_direction_input	Set a GPIO as an input port.
gpio_direction_output	Set a GPIO as an output port.
gpio_get_value	Get the input level of an input pin.
gpio_set_value	Set the level of an output pin.
sstar_gpio_pad_set	Set a pin as GPIO mode.
sstar_gpio_pad_clr	Clear a pin as GPIO mode.
sstar_gpio_pad_val_set	Set the TMUX mode of a pin.
sstar_gpio_pad_val_get	Configured PadMode of a certain Pad.
sstar_gpio_vol_val_set	Set the voltage mode of a pin.
sstar_gpio_pad_in_out	Get the state of a pin.
sstar_gpio_pull_up	Enable the pull-up function of a specific GPIO.
sstar_gpio_pull_down	Enable the pull-down function of a specific GPIO.
sstar_gpio_pull_off	Disable the pull-up/pull-down and switch to the floating state.
sstar_gpio_pull_status	Get the pull-up/pull-down state of a specific GPIO.
sstar_gpio_drv_set	Set the driving strength of a specific GPIO.
sstar_gpio_drv_get	Get the level of driving strength of a specific GPIO.
sstar_gpio_to_irq	Get the IRQ index of a specific GPIO.
sstar_gpio_name_to_num	Get the GPIO Index based on the GPIO Name.
sstar_gpio_padmode_to_padindex	Query all GPIO pins that can use a specific PadMode.
mdrv_padmux_getpad	Use Puse as the search condition to obtain the Pad configured.
mdrv_padmux_getmode	Use Puse as the search condition to obtain the Tmux Mode configured.
mdrv_padmux_getpuse	Puse can be obtained according to these three parameters.

7.1. gpio_request¶

Purpose

Create a GPIO port.

Syntax

int gpio_request(unsigned gpio, const char *label)

Parameter

Parameter Name Description

gpio GPIO Index

label GPIO name
Return Value

Return Value Description

0 Success

other Fail

7.2. gpio_free¶

Purpose

Free a GPIO port.
Syntax
```
void gpio_free(unsigned gpio)
```
Parameter

Parameter Name Description

gpio GPIO Index
Return Value

None void

Description Return Value

7.3. gpio_direction_input¶

Purpose

Set a GPIO as an input port.

Syntax

int gpio_direction_input(unsigned gpio);

Parameter

Parameter Name Description

gpio GPIO Index
Return Value

Return Value Description

0 Success

other Fail

7.4. gpio_direction_output¶

Purpose

Set a GPIO as an output port.

Syntax

int gpio_direction_output(unsigned gpio, int value);

Parameter

Parameter Name Description

gpio GPIO Index

value Output value
Return Value

Return Value Description

0 Success

other Fail

7.5. gpio_get_value¶

Purpose

Get the input level of an input pin.
Syntax
```
int gpio_get_value(unsigned gpio);
```
Parameter

Parameter Name Description

gpio GPIO Index
Return Value

Return Value Description

int Level value

7.6. gpio_set_value¶

Purpose

Set the level of an output pin.

Syntax

void gpio_set_value(unsigned gpio, int value);

Parameter

Parameter Name Description

gpio GPIO Index

value Output value
Return Value

Return Value Description

0 Success

other Fail

7.7. sstar_gpio_pad_set¶

Purpose

Set a pin as GPIO mode.

Syntax

void sstar_gpio_pad_set(U8 gpio_index);

Parameter

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

void None

7.8. sstar_gpio_pad_clr¶

Purpose

Clear the GPIO mode of a pin.

Syntax

void sstar_gpio_pad_clr(U8 gpio_index);

Parameter

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

void None

7.9. sstar_gpio_pad_val_set¶

Purpose

Set the TMUX mode of a pin.

Syntax

U8 sstar_gpio_pad_val_set(U8 gpio_index, U32 pad_mode);

Parameter

Parameter Name Description

gpio_index GPIO Index

pad_mode TMUX MODE
Return Value

Return Value Description

1 Incorrect input parameter

0 Success

7.10. sstar_gpio_pad_val_get¶

Purpose

This API is used to get the currently configured PadMode of a certain Pad, provided that when configuring PadMode for this Pad, it is configured through the Padmux interface. Directly operating registers for configuration will not make this API effective.

Syntax

U8 sstar_gpio_pad_val_get(U8 gpio_index, U32* pad_mode);

Parameter

Parameter Name Description

gpio_index Group Index

pad_mode The TMUX MODE gotten
Return Value

Return Value Description

1 Incorrect output parameter

0 Success

7.11. sstar_gpio_vol_val_set¶

Purpose

Set the voltage mode of a pin. Note that this API is only supported by Muffin.

Syntax

void sstar_gpio_vol_val_set(U8 group, U32 mode);

Parameter

Parameter Name Description

group Group num (11 Groups in total)

mode Mode = 0: Voltage of the pin is 3.3V; Mode = 1: Voltage of the pin is 1.8V
Return Value

Return Value Description

void None

7.12. sstar_gpio_pad_in_out¶

Purpose

Get the state of a pin.

Syntax

U8 sstar_gpio_pad_in_out(U8 gpio_index, U8* pad_in_out);

Parameter

Parameter Name Description

gpio_index GPIO Index

pad_in_out 1 means the pin is in output state; 0 means the pin is in input state
Return Value

Return Value Description

1 Incorrect input parameter

0 Success

7.13. sstar_gpio_pull_up¶

Purpose

Enable the pull-up function of a specific GPIO.
Syntax
```
U8 sstar_gpio_pull_up(U8 gpio_index);
```
Parameter

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

0 Success

other Pull-up function not supported by the pin or incorrect input parameter

7.14. sstar_gpio_pull_down¶

Purpose

Enable the pull-down function of a specific GPIO.

Syntax

U8 sstar_gpio_pull_down(U8 gpio_index);

Parameter

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

0 Success

other Pull-down function not supported by the pin or incorrect input parameter

7.15. sstar_gpio_pull_off¶

Purpose

Disable the pull-up/pull-down function of a specific GPIO and switch to the floating state.
Syntax
```
U8 sstar_gpio_pull_off(U8 gpio_index);
```
Parameter

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

0 Success

other Pull-up function not supported by the pin or incorrect input parameter

7.16. sstar_gpio_pull_status¶

Purpose

Get the pull-up/pull-down state of a specific GPIO.

Syntax

U8 sstar_gpio_pull_status(U8 gpio_index, U8* pull_status);

Parameter

Parameter Name Description

gpio_index GPIO Index

pull_status The pull-up/pull-down state gotten
Return Value

Return Value Description

0 Success

1 Pull-up function not supported by the pin or incorrect input parameter

7.17. sstar_gpio_drv_set¶

Purpose

Set the driving strength of a specific GPIO.

Syntax

U8 sstar_gpio_drv_set(U8 gpio_index, U8 level);

Parameter

Parameter Name Description

gpio_index GPIO Index

level Level of the driving strength
Return Value

Return Value Description

0 Success

other Driving strength configuration not supported by the pin or incorrect input parameter

7.18. sstar_gpio_drv_get¶

Purpose

Get the level of driving strength of a specific GPIO.

Syntax

U8 sstar_gpio_drv_get(U8 gpio_index, U8* level);

Parameter

Parameter Name Description

gpio_index GPIO Index

level The level of driving strength gotten
Return Value

Return Value Description

0 Success

1 Driving strength configuration not supported by the pin or incorrect input parameter

7.19. sstar_gpio_to_irq¶

Purpose

Get the IRQ index of a specific GPIO.
Syntax
```
int sstar_gpio_to_irq(U8 gpio_index);
```
Parameter

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

virq The IRQ index returned

Negative number or 0 Fail

7.20. sstar_gpio_name_to_num¶

Purpose

Get the GPIO Index based on the GPIO Name.

Syntax

U8 sstar_gpio_name_to_num(U8* p_name, U8* gpio_index);

Parameter

Parameter Name Description

p_name GPIO Name

gpio_index The GPIO Index gotten
Return Value

Return Value Description

1 Incorrect input parameter

0 Success

7.21. sstar_gpio_padmode_to_padindex¶

Purpose

Query all GPIO pins that can use a specific PadMode.

Syntax

U32* sstar_gpio_padmode_to_padindex(U32 mode);

Parameter

Parameter Name Description

mode The PadMode to be queried
Return Value

Return Value Description

Array start address The array in which the GPIO Index is stored

7.22. mdrv_padmux_getpad¶

Purpose

Use Puse as the search condition to obtain the Pad configured in xxx-padmux.dtsi.
Syntax
```
int mdrv_padmux_getpad (int Puse);
```
Parameter

Parameter Name Description

Puse Puse macro definition
Return Value

Return Value Description

PadId Pad macro definition has been successfully gotten from padmux.dtsi

PAD_UNKNOWN The input Puse is incorrect or corresponding PadId is not found in padmux.dtsi

7.23. mdrv_padmux_getmode¶

Purpose

Use Puse as the search condition to obtain the Tmux Mode configured in xxx-padmux.dtsi.
Syntax
```
int mdrv_padmux_getmode (int Puse);
```
Parameter

Parameter Name Description

Puse Puse macro definition
Return Value

Return Value Description

PadId Pad macro definition has been successfully gotten from padmux.dtsi

PAD_UNKNOWN The input Puse is incorrect or corresponding PadId is not found in padmux.dtsi

7.24. mdrv_padmux_getpuse¶

Purpose

The macro definition of PUSE follows a set of rules:
1. The offset between different IPs is 0x10000
2. The offset between different Channels in the same IP is 0x100
3. The offset between different Puses in the same channel with the same IP is 0x1
As such, the macro definition of Puse can be obtained according to these three parameters.

Syntax

int mdrv_padmux_getpuse (int IP_Index, int Channel_Index, int Pad_Index);

Parameter

Parameter Name	Description
IP_Index	The IP where the Puse is located, which can be found in mdrv_puse.h
Channel_Index	The Channel where the Puse is located, which can be found in mdrv_puse.h
Pad_Index	The Index of the Puse in channel, which can be found in mdrv_puse.h

Return Value

Return Value Description

Puse PadId has been successfully gotten from padmux.dtsi

8. FAQ¶

When there is an exception in operating gpio, you can refer to the following points for debugging.

Questions	Resolution
Export cannot pull high or low	The voltmeter actually measures, write directly to the register
Padmode exception	Use the iocheck tool to check if the padmode setting is correct

8.1. Export cannot pull high or low¶

Operate the register corresponding to the gpio pin to pull up and down, use a voltmeter to measure for any changes, and locate whether the cat value or set value is incorrect.

8.2. Padmode exception¶

In the kernel/stard/drivers/gpio/ut/io_check directory, simply make to generate the prog_iocheck tool, package it to the customer partition, and start using it.

The supported options are as follows:

Option	Function
-s	set padmux mode
-g	get padmux mode
-i	Specify pin index
-m	Specify mode
-v	Verify Padmux mode conflicts

Example: To query a certain gpio pin, its index is index

Query the current reuse status: ./prog_io_check -i index

Set as corresponding mode: ./prog_io_check -i index -m mode_index -s

Parameter Name	Description
group	Group num (11 Groups in total)
mode	Mode = 0: Voltage of the pin is 3.3V; Mode = 1: Voltage of the pin is 1.8V

Parameter Name	Description
gpio_index	GPIO Index
pad_in_out	1 means the pin is in output state; 0 means the pin is in input state

Return Value	Description
0	Success
other	Pull-up function not supported by the pin or incorrect input parameter

Return Value	Description
0	Success
other	Pull-down function not supported by the pin or incorrect input parameter

Parameter Name	Description
gpio_index	GPIO Index
pull_status	The pull-up/pull-down state gotten

Return Value	Description
0	Success
other	Driving strength configuration not supported by the pin or incorrect input parameter

Parameter Name	Description
gpio_index	GPIO Index
level	The level of driving strength gotten

Return Value	Description
PadId	Pad macro definition has been successfully gotten from padmux.dtsi
PAD_UNKNOWN	The input Puse is incorrect or corresponding PadId is not found in padmux.dtsi

GPIO User Guide

1. Overview¶

2. Keyword¶

2.1. GPIO Index¶

3. Function Description¶

4. Hardware Connection¶

5. Uboot Usage¶

5.1. Uboot Config¶

5.2. Related Code Path¶

5.3. DTS Parameter Configuration¶

5.4. Uboot Command Parameter¶

5.5. Uboot Command Usage Example¶

5.6. Pin initial state setting¶

5.6.1. Uboot Config¶

5.6.2. Function usage instructions¶

6. Kernel Usage¶

6.1. Kernel Config¶

6.2. Related Code Path¶

6.3. DTS Parameter Configuration¶

6.4. Module Usage Introduction¶

6.4.1. The export/unexport File Interface¶

6.4.2. /sys/class/gpio/gpioN¶

6.4.3. /sys/class/sstar/msys¶

6.4.4. Usage of Multiplexing Function¶

6.4.5. Pin initial state setting¶

6.5. Sample Code¶

6.5.1 User space interruption¶

6.5.2 API USE Reference¶

7. API Reference¶

7.1. gpio_request¶

7.2. gpio_free¶

7.3. gpio_direction_input¶

7.4. gpio_direction_output¶

7.5. gpio_get_value¶

7.6. gpio_set_value¶

7.7. sstar_gpio_pad_set¶

7.8. sstar_gpio_pad_clr¶

7.9. sstar_gpio_pad_val_set¶

7.10. sstar_gpio_pad_val_get¶

7.11. sstar_gpio_vol_val_set¶

7.12. sstar_gpio_pad_in_out¶

7.13. sstar_gpio_pull_up¶

7.14. sstar_gpio_pull_down¶

7.15. sstar_gpio_pull_off¶

7.16. sstar_gpio_pull_status¶

7.17. sstar_gpio_drv_set¶

7.18. sstar_gpio_drv_get¶

7.19. sstar_gpio_to_irq¶

7.20. sstar_gpio_name_to_num¶

7.21. sstar_gpio_padmode_to_padindex¶

7.22. mdrv_padmux_getpad¶

7.23. mdrv_padmux_getmode¶

7.24. mdrv_padmux_getpuse¶

8. FAQ¶

8.1. Export cannot pull high or low¶

8.2. Padmode exception¶