GPIO User Guide¶

REVISION HISTORY¶

Revision No.	Description	Date
1.0	Initial release	01/22/2024
1.1	Added Chapter 8 DEBUG & FAQ	11/08/2025

1. Overview¶

General Purpose Input/Output (GPIO) is abbreviated as GPIO. GPIO uses the standard Linux framework, enabling unified interface operations.

Figure 1-1 GPIO Framework Diagram

The GPIO framework is shown in the diagram above. The middle layer is gpiolib, which manages the GPIO in the system. gpiolib summarizes the general operations of GPIO. Based on the characteristics of GPIO, gpiolib provides a unified and universal software interface for operating GPIO to the upper layers (other drivers). Lower layers, gpiolib provides a framework for different chip operations. For different chips, only mdrv_gpio_io.c needs to be implemented, and then the registration function provided by gpiolib is used to connect it to gpiolib.

2. Keyword Explanation¶

2.1. GPIO Index¶

The GPIO pad name on the schematic can be found in Table 1-1 to determine the corresponding GPIO Index. The GPIO Index is used as an input parameter for software functions that operate on the GPIO.

For example: If the desired GPIO is PAD_GPIO4, the corresponding GPIO Index found in Table 1-1 is 12.

Table 1-1: GPIO Index and PAD Correspondence Table

Pad Name	GPIO Index	Pad Name	GPIO Index	Pad Name	GPIO Index
PAD_I2C1_SDA	0	PAD_SR_RST0	1	PAD_SR_MCLK0	2
PAD_I2C1_SCL	3	PAD_SR_RST1	4	PAD_SR_MCLK1	5
PAD_I2C2_SCL	6	PAD_I2C2_SDA	7	PAD_GPIO0	8
PAD_GPIO1	9	PAD_GPIO2	10	PAD_GPIO3	11
PAD_GPIO4	12	PAD_GPIO5	13	PAD_GPIO6	14
PAD_GPIO7	15	PAD_GPIO8	16	PAD_GPIO9	17
PAD_GPIO10	18	PAD_GPIO11	19	PAD_SD0_CDZ	20
PAD_SD0_D1	21	PAD_SD0_D0	22	PAD_SD0_CLK	23
PAD_SD0_CMD	24	PAD_SD0_D3	25	PAD_SD0_D2	26
PAD_FUART_RTS	27	PAD_FUART_CTS	28	PAD_FUART_RX	29
PAD_FUART_TX	30	PAD_MSPI_CZ	31	PAD_MSPI_DO	32
PAD_MSPI_DI	33	PAD_MSPI_CK	34	PAD_SPI0_DO	35
PAD_SPI0_DI	36	PAD_SPI0_HLD	37	PAD_SPI0_WPZ	38
PAD_SPI0_CZ	39	PAD_SPI0_CK	40	PAD_I2C0_SDA	41
PAD_I2C0_SCL	42	PAD_PM_GPIO12	43	PAD_PM_GPIO11	44
PAD_PM_UART_TX	45	PAD_PM_UART_RX	46	PAD_PM_PSPI0_INT	47
PAD_PM_PSPI0_DI	48	PAD_PM_PSPI0_DO	49	PAD_PM_PSPI0_CK	50
PAD_PM_PSPI0_CZ	51	PAD_PM_GPIO10	52	PAD_PM_GPIO9	53
PAD_PM_GPIO8	54	PAD_PM_GPIO7	55	PAD_PM_PWM3	56
PAD_PM_PWM2	57	PAD_PM_PWM1	58	PAD_PM_PWM0	59
PAD_PM_GPIO6	60	PAD_PM_GPIO5	61	PAD_PM_GPIO4	62
PAD_PM_UART2_TX	63	PAD_PM_UART2_RX	64	PAD_PM_I2C_CLK	65
PAD_PM_I2C_SDA	66	PAD_PM_SDIO_INT	67	PAD_PM_GPIO3	68
PAD_PM_GPIO2	69	PAD_PM_GPIO1	70	PAD_PM_GPIO0	71
PAD_PM_SDIO_D1	72	PAD_PM_SDIO_D0	73	PAD_PM_SDIO_CLK	74
PAD_PM_SDIO_CMD	75	PAD_PM_SDIO_D3	76	PAD_PM_SDIO_D2	77
PAD_PM_FUART_RTS	78	PAD_PM_FUART_CTS	79	PAD_PM_FUART_RX	80
PAD_PM_FUART_TX	81	PAD_PM_HSRAM_GPIO0	82	PAD_PM_HSRAM_GPIO1	83
PAD_PM_HSRAM_GPIO2	84	PAD_PM_HSRAM_GPIO3	85	PAD_PM_HSRAM_GPIO4	86
PAD_PM_HSRAM_GPIO5	87	PAD_PM_HSRAM_GPIO6	88	PAD_PM_HSRAM_GPIO7	89
PAD_PM_HSRAM_GPIO8	90	PAD_PM_HSRAM_GPIO9	91	PAD_PM_HSRAM_GPIO10	92
PAD_PM_HSRAM_GPIO11	93	PAD_PM_HSRAM_GPIO12	94	PAD_PM_SAR_GPIO0	95
PAD_PM_SAR_GPIO1	96	PAD_PM_SAR_GPIO2	97	PAD_PM_SAR_GPIO3	98
PAD_PM_SAR_GPIO4	99	PAD_OUTN_RX0_CH5	100	PAD_OUTP_RX0_CH5	101
PAD_OUTN_RX0_CH4	102	PAD_OUTP_RX0_CH4	103	PAD_OUTN_RX0_CH3	104
PAD_OUTP_RX0_CH3	105	PAD_OUTN_RX0_CH2	106	PAD_OUTP_RX0_CH2	107
PAD_OUTN_RX0_CH1	108	PAD_OUTP_RX0_CH1	109	PAD_OUTN_RX0_CH0	110
PAD_OUTP_RX0_CH0	111

3. Function Description¶

Supports configuring the pull-up/pull-down state of GPIO pins
Supports configuring the drive capability of GPIO pins

4. Hardware Connection¶

Simply connect the corresponding GPIO pin to the hardware.

5. U-Boot Usage Introduction¶

5.1. U-Boot Config Description¶

[*] SigmaStar drivers --->

    [*] SigmaStar GPIO

    [*] SigmaStar padmux

drivers/sstar/gpio/drv_gpio.c
drivers/sstar/gpio/drv_gpio.h
drivers/sstar/gpio/chip_name/hal_gpio.c
drivers/sstar/gpio/chip_name/hal_gpio.h
drivers/sstar/gpio/chip_name/hal_pinmux.c
drivers/sstar/gpio/chip_name/hal_pinmux.h
drivers/sstar/include/chip_name/gpio.h
drivers/sstar/include/chip_name/padmux.h

5.3. DTS Parameter Configuration Instructions¶

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

Attributes	Description	Remarks
compatible	Used for driver matching and registration	Modification prohibited
status	Driver on/off	Configure as needed, ok/disabled

5.4. Uboot cmd Parameter Description¶

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

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

cmd	Parameters	Description
input	pin	Sets the pin with pin number pin to GPIO input mode
set	pin	Sets the pin with pin number pin to GPIO output high mode
clear	pin	Sets the pin with pin number pin to GPIO output low mode
toggle	pin	Toggle the voltage level of the pin with pin number pin

5.5. Uboot cmd usage examples¶

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

6. Kernel Usage Introduction¶

6.1. Kernel config Configuration Instructions¶

Device Drivers  --->

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

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

drivers/sstar/gpio/drv/drv_gpio.c
drivers/sstar/gpio/drv/drv_gpio.h
drivers/sstar/gpio/hal/chip_name/src/hal_gpio.c
drivers/sstar/gpio/hal/chip_name/inc/hal_gpio.h
drivers/sstar/gpio/hal/chip_name/src/hal_gpio_common.c
drivers/sstar/gpio/hal/chip_name/src/hal_pinmux.c
drivers/sstar/gpio/hal/chip_name/inc/hal_pinmux.h
drivers/sstar/gpio/hal//chip_name/pub/gpio.h
drivers/sstar/gpio/hal/chip_name/pub/padmux.h
drivers/sstar/gpio/os/gpio_os.h
drivers/sstar/gpio/ut/gpio_irq_test.c

6.3. DTS Parameter Configuration Instructions¶

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

Attributes	Description	Remarks
compatible	Used for driver matching and registration	Modification is prohibited
#gpio-cells	Declares the number of GPIO cells in the device node	Configuring it to 2 means the first cell is the GPIO number, and the second cell represents the active GPIO level
status	Driver on/off	Configure as needed, ok/disabled

6.4. Module Usage Introduction¶

6.4.1. Export/Unexport File Interface¶

Userspace can manipulate GPIOs via the sysfs interface.

The source code for /sys/class/gpio is located in driver/gpio/gpiolib-sysfs.c.

The /sys/class/gpio directory contains three files: export/unexport, gpioN, and gpio_chipN.

Filename	Read/Write Permissions	Value	Description
export	wo	GPIO Index	Requests control of a specific GPIO in user space
unexport	wo	GPIO Index	Removes control of a specific GPIO from user space
gpioN	ro		Contains information such as the direction and value of the specific GPIO
gpio_chipN	ro		Refers to the GPIO controller

The GPIO index can be found in drivers/sstar/include/CHIPNAME/gpio.h

The file /sys/class/gpio/export is write-only. User programs request control of a specific GPIO port from the kernel (sysfs) by writing its number, provided no kernel code has already requested that port. For example, the command to request GPIO port number 12 is:
```
# echo 12 > export
```
The above operation will create a node gpio12 for GPIO with GPIO Index 12. At this time, a directory gpio12 will be generated under the /sys/class/gpio directory, as shown in the figure below:
/sys/class/gpio/unexport The file attributes are also set to write-only, the opposite of export. Users remove user-space (sysfs) interfaces by writing the GPIO number. For example, the command to remove the gpio12 folder is:
```
# echo 12 > unexport
```
The above operation will remove the gpio12 node, as shown in the following figure:

6.4.2. /sys/class/gpio/gpioN¶

/sys/class/gpio/gpioN refers to a specific GPIO port, and contains the following property file:

file name	Read and write permissions	value	describe
direction	rw	in	Input mode, value is not writable
		out	Output mode, value is writable
		high	Output status: default is high level; value can be written.
		low	Output status: default low level; value can be written.
value	rw	1	high level state
value	rw	0	low level state
edge	rw	none	disable GPIO interrupt
		rising	Enable GPIO interrupts and set them to rise-edge triggered.
		falling	Enable GPIO interrupts and set them to fall-edge triggered.
		both	Enable GPIO interrupts and set them to double-edge triggered.

direction Indicates the direction of the GPIO port; the read result is either in or out. The read command is:

# cat direction

value This indicates the voltage level of the GPIO pin, where 0 represents low and 1 represents high. The read command is:

# cat value

Write operations can be performed on a direction using the following command:

# echo in > direction

# echo out > direction

If the direction is configured as output (out), the level is low by default, and the value is writable. The operation command is:

# echo 1 > value

# echo 0 > value

When writing "direction" to "low" or "high", it can not only be set as output but also specify a particular output level. The operation command is:

# echo high > direction

# echo low > direction

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

edge indicates whether to enable GPIO interrupts and sets the trigger mode, supporting rising edge triggering, falling edge triggering, and double edge triggering:

# cat edge

You can perform write operations on the edge using the following command:

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

If you need to enable an interrupt for a certain pin, you need to first set that pin to the input state and set the trigger mode. Then you can call the poll(2) function to listen for the interrupt. After the interrupt is triggered, the poll(2) function will return.

6.4.3. /sys/class/sstar/msys¶

The Linux GPIO framework does not currently support GPIO pull-up/pull-down and drive capability adjustment configurations. In addition to the standard Linux GPIO framework, we have added an extra file interface for manipulating GPIO pull-up/pull-down and adjusting drive capabilities. To support this feature, you first need to enable the CONFIG_MSYS_GPIO configuration, which is located in menuconfig.

Device Drivers  --->

    [*] SStar SoC platform drivers  --->
        [*]   support GPIO pull and driving modify
        [*]   support padmux modify and verify

The source code for /sys/class/sstar/msys is located in driver/sstar/msys/ms_msys.c.

Before setting up pull-up/pull-down, the GPIO must first be set to input mode. Output pull-up/pull-down states cannot be measured.

After setting the pin to input mode, navigate to the sys/class/mstar/msys folder:

gpio_pull You can write up and down.

file name	Read and write permissions	value	describe
gpio_pull	rw	up	Pull-up mode
gpio_pull	rw	down	drop-down mode

To check the current pull status of GPIO, see pull up / pull down / pull off:

1. # echo 50 >  gpio_pull
2. # cat gpio_pull

An error will occur if an invalid GPIO Index and GPIO Name are entered:

The commands to set the drop-up and drop-down are:

1. # echo 50 up > gpio_pull
2. # echo 50 down > gpio_pull

After setting it, check the status of gpio_pull, as shown in the figure below. 50 represents the GPIO Index, and PAD_OUTN_RX0_CH3 represents the GPIO Name.

1. # cat gpio_pull

An error will occur if an invalid GPIO Index and GPIO Name are entered:

To check if a specific bit has been written correctly, you can look up the corresponding PAD in the GPIO_Mapping_Table (see GPIO INDEX: 50 in the image below). When pulling up, the PE bit is 1 and the PS bit is 0; when pulling down, the PE bit is 1 and the PS bit is 0. The specific operation command is as follows:

1. # riu_r 0x103e 0x34

Check BIT6 and BIT11 of the riu_r return value.

gpio_drive The level that can be written to the driver

Filename Read/Write Permissions Value Description

gpio_drive rw 0~8 Sets the GPIO drive level

The driver capability level of GPIO in the current platform can be found in the GPIO_Mapping_Table.

To view the command bit for the initial driver capability level of a GPIO: (Alternatively, you can directly use the GPIO43 name PAD_OUTP_RX0_CH0)
```
1. # echo 43 > gpio_drive
2. # cat gpio_drive
```
An error will occur if an invalid GPIO Index and GPIO Name are entered:

Before configuring the drive capability, set the GPIO to a high-level output state for easy measurement. The configuration command is:
```
1. # echo 43 1 > gpio_drive
```
43 represents the GPIO Index, and 1 represents the drive capability level, corresponding to 4mA.

After setting the drive capability, check the status of gpio_driver. As shown in the figure below, setting the drive capability of the pin with GPIO Index 43 to 4mA was successful.
```
1. # cat gpio_drive
```
To check if a specific bit has been written correctly, you can look up the corresponding pad in the GPIO_Mapping_Table (see GPIO INDEX: 50 in the image below). When the driver level is set to 1, [103E56]#7 ~ #8 are 01. The specific operation command is:
```
1. # riu_r 0x103e 0x2B
```
Check the BIT7 and BIT8 of the riu_r return value.
mux_verify Used to identify reuse conflicts

Filename Read/Write Permissions Value Description

mux_verify rw 0~8 Confirm if there are any conflicts in the reuse functionality

Taking the operation of PAD_I2C1_SDA's PINMUX_FOR_I2C1_MODE_1 as an example:
```
1. # echo PAD_I2C1_SDA I2C1_MODE_1 > /sys/class/sstar/msys/mux_verify
2. # cat mux_verify
```
The following display indicates that the settings are correct and there are currently no reuse conflicts.

The following display indicates that a reuse issue exists.
```
Please check register value of [bank: 0x103E, offset: 0x00, mask: 0x0008]
Correct value is not 0x0008, but current value is 0x0008
```
The problematic register address is: [bank: 0x103E, offset: 0x00, mask: 0x0008]. The correct value is not 0x0008 because the mask is 0x0008 (BIT3 == 0x0008), so BIT3 should be 0. However, BIT3 is currently equal to 1, and BIT3 needs to be cleared.
```
Please check register value of [bank: 0x103C, offset: 0x53, mask: 0x0003]
Correct value is 0x0001, but current value is 0x0000
```
The problematic register address is: [bank: 0x103C, offset: 0x53, mask: 0x0003]. The correct value is 0x0001 because the mask is 0x0003 (BIT1|BIT0==0x0003). Therefore, BIT0 should be 1 and BIT1 should be 0.
mux_modify Used to configure multiplexing functionality

Filename Read/Write Permissions Value Description

mux_modify rw 0~8 Configure multiplexing functionality

Taking PINMUX_FOR_I2C1_MODE_1 for PAD_I2C1_SDA as an example:

6.4.4. Multiplexing Function Usage Instructions¶

When using GPIO multiplexing, you first need to obtain the Name of the pin to be operated and the Tmux Mode to be multiplexed, and configure them in xxx-padmux.dtsi:

1. <PAD_VSYNC_OUT PINMUX_FOR_VGA_VSYNC_MODE_1 MDRV_PUSE_VGA_VSYNC>

2. <PAD_HSYNC_OUT PINMUX_FOR_VGA_HSYNC_MODE_1 MDRV_PUSE_VGA_HSYNC>

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

Important points to note during configuration:

A Pad can only be configured with one Mode; multiple Modes cannot be configured on a single Pad simultaneously.
A Puse can only correspond to one set of configurations; otherwise, conflicts will occur. - The configured Pad and Mode must match.
Reuse operations are not allowed directly in the driver; all reused configurations must be centralized in xxx_padmux.dtsi. (Except for configurations that require dynamic adjustment of reused settings, this is for ease of management and to reduce configuration conflicts.)

6.5. Sample Code¶

User-space code enables GPIO interrupt reference demo.

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.    }

7. API参考¶

This functional module provides the following interfaces:

API Name	Function
gpio_request	Request a GPIO port
gpio_free	Release a GPIO port
gpio_direction_input	Mark a GPIO as an input
gpio_direction_output	Mark a GPIO as an output
gpio_get_value	Get the voltage level of an input pin
gpio_set_value	Set the voltage level of an output pin
sstar_gpio_pad_set	Sets the pin to gpio_mode
sstar_gpio_pad_clr	Clears the pin's gpio_mode
sstar_gpio_pad_val_set	Sets the pin's tmux mode
sstar_gpio_pad_val_get	Gets the PadMode currently configured for a specific pad.
sstar_gpio_vol_val_set	Gets the voltage level of an input pin. This interface is only supported by Muffin.
sstar_gpio_pad_in_out	Determines the input/output status of a pin.
sstar_gpio_pull_up	Enables pull-up functionality for a specified GPIO pin.
sstar_gpio_pull_down	Enables pull-down functionality for a specified GPIO pin.
sstar_gpio_pull_off	Disables the specified GPIO pull-up/pull-down functionality and switches it to an unattended state.
sstar_gpio_pull_status	Get the pull-up/pull-down status of the specified GPIO.
sstar_gpio_drv_set	Set the driver capability of the specified GPIO.
sstar_gpio_drv_get	Get the driver capability level of the specified GPIO.
sstar_gpio_to_irq	Get the interrupt number of the GPIO that is known to you.
sstar_gpio_name_to_num	Get the GPIO index by GPIO name.
sstar_gpio_padmode_to_padindex	Queries all GPIO pins that can use a specific padmode.
drv_padmux_getpad	Retrieves the pad configured in the DTSI with puse.
drv_padmux_getmode	Retrieves the tmux mode configured in the DTSI with puse.
drv_padmux_getpuse	Gets the macro definition of puse.

7.1. gpio_request¶

Purpose

Create a GPIO port.

Syntax

int gpio_request(unsigned gpio, const char *label)

Parameters

Parameter Name Description

gpio GPIO Index

label Specific Name
Return Value

Return Value Description

0 Success

other Failure

7.2. gpio_free¶

Purpose

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

Parameter Name Description

gpio GPIO Index
Return Value

Return Value Description

void None

7.3. gpio_direction_input¶

Purpose

Mark GPIO as input.

Syntax

int gpio_direction_input(unsigned gpio);

Parameters

Parameter Name Description

gpio GPIO Index
Return Value

Return Value Description

0 Success

other Failure

7.4. gpio_direction_output¶

Purpose

Mark GPIO as output.

Syntax

int gpio_direction_output(unsigned gpio, int value);

Parameters

Parameter Name Description

gpio GPIO Index

value Output value
Return Value

Return Value Description

0 Success

other Failure

7.5. gpio_get_value¶

Purpose

To obtain the voltage level of an input pin.
Syntax
```
int gpio_get_value(unsigned gpio);
```
Parameters

Parameter Name Description

gpio GPIO Index
Return Value

Return Value Description

int Voltage Level

7.6. gpio_set_value¶

Purpose

Sets the voltage level of an output pin.

Syntax

void gpio_set_value(unsigned gpio, int value);

Parameters

Parameter Name Description

gpio GPIO Index

value Output Value
Return Value

Return Value Description

0 Success

other Failure

7.7. sstar_gpio_pad_set¶

Purpose

Sets the pin to GPIO MODE.

Syntax

void sstar_gpio_pad_set(u8 gpio_index);

Parameters

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 the pin.

Syntax

void sstar_gpio_pad_clr(u8 gpio_index);

Parameters

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

void None

7.9. sstar_gpio_pad_val_set¶

Purpose

Sets the TMUX mode of a pin.

Syntax

u8 sstar_gpio_pad_val_set(u8 gpio_index, u32 pad_mode);

Parameters

Parameter Name Description

gpio_index GPIO Index

pad_mode TMUX MODE
Return Value

Return Value Description

1 Output parameter error

0 Success

7.10. sstar_gpio_vol_val_set¶

Purpose

This API is used to retrieve the current PadMode of a specific Pad, provided that the PadMode was configured via the Padmux interface. Direct register manipulation will not make this API effective.

Syntax

void sstar_gpio_vol_val_set(u8 group, u32 mode);

Parameters

Parameter Name Description

gpio_index Group Index

pad_mode The retrieved TMUX MODE
Return Value

Return Value Description

1 Output parameter error

0 Success

7.11. sstar_gpio_vol_val_set¶

Purpose

To obtain the voltage level of the input pin. Note that this interface is only supported by Muffin.

Syntax

void sstar_gpio_vol_val_set(u8 group, u32 mode);

Parameters

Parameter Name Description

group Group num (11 Groups in total)

mode Mode = 0: Pin voltage is 3.3V; Mode = 1: Pin voltage is 1.8V
Return Value

Return Value Description

void None

7.12. sstar_gpio_pad_in_out¶

Purpose

Determine whether a pin is in the input or output state.

Syntax

u8 sstar_gpio_pad_in_out(u8 gpio_index, u8* pad_in_out);

Parameters

Parameter Name Description

gpio_index GPIO Index

pad_in_out 0 indicates the pin is in the output state, 1 indicates the pin is in the input state
Return Value

Return Value Description

1 Input parameter error

0 Success

7.13. sstar_gpio_pull_up¶

Purpose

Enables pull-up functionality for the specified GPIO pin.
Syntax
```
u8 sstar_gpio_pull_up(u8 gpio_index);
```
Parameters

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

0 Successfully set

other This pin does not support pull-up settings or the input parameter is incorrect

7.14. sstar_gpio_pull_down¶

Purpose

Enables pull-down functionality for the specified GPIO pin.

Syntax

u8 sstar_gpio_pull_down(u8 gpio_index);

Parameters

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

0 Successfully set

other This pin does not support pull-down settings or the input parameter is incorrect

7.15. sstar_gpio_pull_off¶

Purpose

Disables the pull-up/pull-down function of the specified GPIO and switches it to a floating state.
Syntax
```
u8 sstar_gpio_pull_off(u8 gpio_index);
```
Parameters

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

0 Successfully set

other This pin does not support pull-up settings or the input parameter is incorrect

7.16. sstar_gpio_pull_status¶

Purpose

To obtain the pull-up/pull-down status of a specified GPIO pin.

Syntax

u8 sstar_gpio_pull_status(u8 gpio_index, u8* pull_status);

Parameters

Parameter Name Description

gpio_index GPIO Index

pull_status The obtained pull-up/pull-down status
Return Value

Return Value Description

0 Successful acquisition

1 This pin does not support pull-up settings or the input parameters are incorrect

7.17. sstar_gpio_drv_set¶

Purpose

Sets the drive capability of a specified GPIO pin.

Syntax

u8 sstar_gpio_drv_set(u8 gpio_index, u8 level);

Parameters

Parameter Name Description

gpio_index GPIO Index

level Drive capability level
Return Value

Return Value Description

0 Successfully set

other This pin does not support drive capability setting or the input parameter is incorrect

7.18. sstar_gpio_drv_get¶

Purpose

Retrieves the drive capability level of a specified GPIO pin.

Syntax

u8 sstar_gpio_drv_get(u8 gpio_index, u8* level);

Parameters

Parameter Name Description

gpio_index GPIO Index

level The drive capability level of the obtained GPIO pin
Return Value

Return Value Description

0 Successful acquisition

1 The pin does not support drive capability setting or the input parameter is incorrect

7.19. sstar_gpio_to_irq¶

Purpose

Retrieves the interrupt number of a specified GPIO.
Syntax
```
int sstar_gpio_to_irq(u8 gpio_index);
```
Parameters

Parameter Name Description

gpio_index GPIO Index
Return Value

Return Value Description

virq Virq is the returned interrupt number

Negative or 0 Failure

7.20. sstar_gpio_name_to_num¶

Purpose

To obtain the GPIO Index by GPIO Name.

Syntax

u8 sstar_gpio_name_to_num(u8* p_name, u8* gpio_index);

Parameters

Parameter Name Description

p_name GPIO Name

gpio_index GPIO Index obtained
Return Value

Return Value Description

1 Incorrect input parameter

0 Success

7.21. sstar_gpio_padmode_to_padindex¶

Purpose

To query all GPIO pins that can use a specific PadMode.

Syntax

u32* sstar_gpio_padmode_to_padindex(u32 mode);

Parameters

Parameter Name Description

mode The PadMode to query
Return Value

Return Value Description

Array start address Array storing GPIO Indexes

7.22. drv_padmux_getpad¶

Purpose

Use Puse as the search criterion to retrieve the Pads configured in xxx-padmux.dtsi.
Syntax
```
int drv_padmux_getpad (int Puse);
```
Parameters

Parameter Name Description

Puse Macro definition of Puse
Return Value

Return Value Description

PadId Successfully retrieved the macro definition of Pad in padmux.dtsi

PAD_UNKNOWN The input Puse is incorrect or there is no corresponding PadId in padmux.dtsi

7.23. drv_padmux_getmode¶

Purpose

To retrieve the Tmux Mode configured in xxx-padmux.dtsi by iterating through the database using Puse as the search criterion.
Syntax
```
int drv_padmux_getmode (int Puse);
```
Parameters

Parameter Name Description

Puse Macro definition of Puse

Return Value

Return Value	Description
PadId	Successfully retrieved the macro definition of Mode from padmux.dtsi
PAD_UNKNOWN	The input Puse is incorrect or there is no corresponding PadId in padmux.dtsi

7.24. drv_padmux_getpuse¶

Purpose

Because the macro definition of PUSE follows a set of rules:
1. The offset between different IPs is 0x10000
2. The offset between different Channels within the same IP is 0x100
3. The offset between different Puse instances within the same Channel of the same IP is 0x1
Therefore, the macro definition of Puse can be obtained based on these three parameters.

Syntax

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

Parameters

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

Return Value

Return Value Description

Puse Successfully retrieved the PadId from padmux.dtsi

8. FAQ¶

When encountering errors while operating GPIO, please refer to the following points for troubleshooting:

Common Problems	Troubleshooting Directions
export cannot pull high or low	Actual voltmeter measurement, direct write to register
padmode error	Use the iocheck tool to check if the padmode setting is correct

8.1. Direct Register Writing¶

Pull the register of the corresponding GPIO pin high or low, and use a voltmeter to measure any changes to determine whether the error is due to an incorrect CAT value or a incorrect SET value.

8.2. Using the iocheck Tool¶

In the directory kernel/drivers/sstar/gpio/ut/io_check, simply run make to generate the prog_io_check tool. Package it to the customer partition and it's ready to boot and use.

Supported options are as follows:

Option	Function
-s	Set padmux mode
-g	Get padmux mode
-i	Specify pin number
-m	Specify mode
-v	Check padmux mode conflict

Example: Query a GPIO pin with its index:

Query current multiplexing status: ./prog_io_check -i index

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

Parameter Name	Description
group	Group num (11 Groups in total)
mode	Mode = 0: Pin voltage is 3.3V; Mode = 1: Pin voltage is 1.8V

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

Return Value	Description
0	Successfully set
other	This pin does not support pull-up settings or the input parameter is incorrect

Return Value	Description
0	Successfully set
other	This pin does not support pull-down settings or the input parameter is incorrect

Parameter Name	Description
gpio_index	GPIO Index
pull_status	The obtained pull-up/pull-down status

Return Value	Description
0	Successful acquisition
1	This pin does not support pull-up settings or the input parameters are incorrect

Return Value	Description
0	Successfully set
other	This pin does not support drive capability setting or the input parameter is incorrect

Parameter Name	Description
gpio_index	GPIO Index
level	The drive capability level of the obtained GPIO pin

Return Value	Description
0	Successful acquisition
1	The pin does not support drive capability setting or the input parameter is incorrect

Return Value	Description
virq	Virq is the returned interrupt number
Negative or 0	Failure

GPIO User Guide¶

REVISION HISTORY¶

1. Overview¶

2. Keyword Explanation¶

2.1. GPIO Index¶

3. Function Description¶

4. Hardware Connection¶

5. U-Boot Usage Introduction¶

5.1. U-Boot Config Description¶

5.2. Related Code Paths¶

5.3. DTS Parameter Configuration Instructions¶

5.4. Uboot cmd Parameter Description¶

5.5. Uboot cmd usage examples¶

6. Kernel Usage Introduction¶

6.1. Kernel config Configuration Instructions¶

6.2. Related Code Paths¶

6.3. DTS Parameter Configuration Instructions¶

6.4. Module Usage Introduction¶

6.4.1. Export/Unexport File Interface¶

6.4.2. /sys/class/gpio/gpioN¶

6.4.3. /sys/class/sstar/msys¶

6.4.4. Multiplexing Function Usage Instructions¶

6.5. Sample Code¶

7. API参考¶

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_vol_val_set¶

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. drv_padmux_getpad¶

7.23. drv_padmux_getmode¶

7.24. drv_padmux_getpuse¶

8. FAQ¶

8.1. Direct Register Writing¶

8.2. Using the iocheck Tool¶