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PI4IOE5V9522 GPIO Expander Driver #11

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ea69a6e
added pi4ioe5 to i2c_device_id
katestingle Jan 21, 2026
1c78cbe
Added Reset Pin functionality
katestingle Feb 13, 2026
421538e
working hours reset function and error 1st edits
katestingle Mar 3, 2026
1b456df
reorganized function placement, finished auto reset implementation ex…
katestingle Mar 30, 2026
df770ee
added pca953x_get() reset automation
katestingle Mar 31, 2026
339775c
added printk() test statements & fixed minor syntax errs
katestingle Apr 1, 2026
40b4e39
init HIL debug
katestingle Apr 2, 2026
a1d37b9
probe init edit
katestingle Apr 6, 2026
c6dd6bb
uncomment printk()'s in write/read reg
katestingle Apr 6, 2026
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222 changes: 189 additions & 33 deletions drivers/gpio/pca953x.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,14 +15,22 @@
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/i2c/pca953x.h>

#include <linux/delay.h>
#include <linux/errno.h>

#include <asm/gpio.h>
extern int at91_set_gpio_value(unsigned pin, int value);

#define PCA953X_INPUT 0
#define PCA953X_OUTPUT 1
#define PCA953X_INVERT 2
#define PCA953X_DIRECTION 3

#define RESET_WRITEREG_FAIL -1
#define RESET_SETPIN_FAIL -2
#define RESET_READREG_FAIL -3


static const struct i2c_device_id pca953x_id[] = {
{ "pca9534", 8, },
{ "pca9535", 16, },
Expand All @@ -38,6 +46,7 @@ static const struct i2c_device_id pca953x_id[] = {
{ "pca6107", 8, },
{ "tca6408", 8, },
{ "tca6416", 16, },
{ "pi4ioe5v9539", 16, },
/* NYET: { "tca6424", 24, }, */
{ }
};
Expand All @@ -47,23 +56,37 @@ struct pca953x_chip {
unsigned gpio_start;
uint16_t reg_output;
uint16_t reg_direction;

uint16_t reg_invert;
struct i2c_client *client;
struct gpio_chip gpio_chip;
uint32_t reset_pin_number; // 0 if not resettable, otherwise pin num
};

static int pca953x_write_reg(struct pca953x_chip *chip, int reg, uint16_t val)
{
int ret;

if (chip->gpio_chip.ngpio <= 8)
ret = i2c_smbus_write_byte_data(chip->client, reg, val);
else
else
ret = i2c_smbus_write_word_data(chip->client, reg << 1, val);

if (ret < 0) {
dev_err(&chip->client->dev, "failed writing register\n");
return ret;
printk("*** write reg INIT fail; attempt #1 \n\r");
// fail to write reg: retry 3 times max
int attempts;
attempts = 1;
while(ret < 0 && attempts < 3) {
if (chip->gpio_chip.ngpio <= 8)
ret = i2c_smbus_write_byte_data(chip->client, reg, val);
else
ret = i2c_smbus_write_word_data(chip->client, reg << 1, val);
printk("*** write reg fail; attempt #%d \n\r", attempts+1);
attempts++;
}
if(ret){
printk("*** write reg failed pca953x \n\r");
return ret;
}
}

return 0;
Expand All @@ -79,28 +102,98 @@ static int pca953x_read_reg(struct pca953x_chip *chip, int reg, uint16_t *val)
ret = i2c_smbus_read_word_data(chip->client, reg << 1);

if (ret < 0) {
dev_err(&chip->client->dev, "failed reading register\n");
return ret;
printk("*** read reg INIT fail; attempt #1 \n\r");
int attempts;
attempts = 1;
while(ret < 0 && attempts < 3){
// retry 3 times max
if (chip->gpio_chip.ngpio <= 8)
ret = i2c_smbus_read_byte_data(chip->client, reg);
else
ret = i2c_smbus_read_word_data(chip->client, reg << 1);
printk("*** read reg fail; attempt #%d \n\r", attempts+1);
attempts++;
}
if(ret < 0) {
printk("*** read reg failed pca953x \n\r");
return ret;
}
}

*val = (uint16_t)ret;
return 0;
}

/* Custom reset() function for pi4ioe5v9539 RESET pin:
* can be called assuming chip->reset_pin_number != 0 (assuming reset pin exists)
* Return Codes:
* --> return 0: sucess
* --> return -RESET_WRITEREG_FAIL: failed write to registers after chip reset
* --> return -RESET_SETPIN_FAIL: fail to set RESET pin
*/
static int pca953x_reset(struct pca953x_chip *chip) {
int ret = 0;
// sleep for 25ns to allow the chip to reset
ret = at91_set_gpio_value(chip->reset_pin_number, 1);
if(ret) {
printk("*** RESET: set pin failed before 1st sleep ret=%d\n\r", ret);
return -RESET_SETPIN_FAIL;
}
ndelay(25);
ret = at91_set_gpio_value(chip->reset_pin_number, 0);
if(ret) {
printk("*** RESET: set pin failed after 1st sleep ret=%d\n\r", ret);
return -RESET_SETPIN_FAIL;
}
// sleep for 1 ms to allow the chip to come back up after reset
udelay(1);
// load cache back to registers, except input(mirrors hardware)
ret = pca953x_write_reg(chip, PCA953X_OUTPUT, chip->reg_output);
if(ret<0) {
printk("*** RESET: set pin failed after 2nd sleep ret=%d\n\r", ret);
return -RESET_WRITEREG_FAIL;
}
ret = pca953x_write_reg(chip, PCA953X_DIRECTION, chip->reg_direction);
if(ret) {
printk("*** RESET: write DIRECTION reg failed ret=%d\n\r", ret);
return -RESET_WRITEREG_FAIL;
}
ret = pca953x_write_reg(chip, PCA953X_INVERT, chip->reg_invert);
if(ret) {
printk("*** RESET: write INVERT reg failed ret=%d\n\r", ret);
return -RESET_WRITEREG_FAIL;
}
printk("*** RESET: write DIRECTION reg failed ret=%d\n\r", ret);
return ret;

}

static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
{
struct pca953x_chip *chip;
uint16_t reg_val;
int ret;

chip = container_of(gc, struct pca953x_chip, gpio_chip);

reg_val = chip->reg_direction | (1u << off);
ret = pca953x_write_reg(chip, PCA953X_DIRECTION, reg_val);
if (ret)
return ret;

ret = pca953x_write_reg(chip, PCA953X_DIRECTION, reg_val);
if (ret){
if(chip->reset_pin_number){ // if reset pin exists, attempt to reset
printk("*** GPIO_DIR_INPUT: fail writing DIR register INIT - RESETTING...\n\r");
ret = pca953x_reset(chip);
if(ret == -RESET_SETPIN_FAIL){
printk("*** GPIO_DIR_INPUT: fail setting reset pin\n\r");
dev_err(&chip->client->dev, "failed setting reset pin\n\r");
return ret;
}
ret = pca953x_write_reg(chip, PCA953X_DIRECTION, reg_val);
}
if(ret){
printk("*** GPIO_DIR_INPUT: Complete fail writing DIR register\n\r");
dev_err(&chip->client->dev, "failed writing register\n\r");
return ret;
}
}
chip->reg_direction = reg_val;
printk("*** GPIO_DIR_INPUT: write_reg & [reset passed/not entered]; : DIR reg_val: %d\n\r", reg_val);
return 0;
}

Expand All @@ -115,23 +208,51 @@ static int pca953x_gpio_direction_output(struct gpio_chip *gc,

/* set output level */
if (val)
reg_val = chip->reg_output | (1u << off);
reg_val = chip->reg_output | (1u << off); // set the bit
else
reg_val = chip->reg_output & ~(1u << off);
reg_val = chip->reg_output & ~(1u << off); // clear the bit

ret = pca953x_write_reg(chip, PCA953X_OUTPUT, reg_val);
if (ret)
return ret;
if(chip->reset_pin_number){ // if reset pin exists, attempt to reset
printk("*** GPIO_DIR_OUTPUT: fail writing OUTPUT register INIT - RESETTING...\n\r");
ret = pca953x_reset(chip);
if(ret == -RESET_SETPIN_FAIL) {
printk("*** GPIO_DIR_OUTPUT: fail setting reset pin post write OUTPUT reg fail\n\r");
dev_err(&chip->client->dev, "failed setting reset pin\n");
return ret;
}
ret = pca953x_write_reg(chip, PCA953X_OUTPUT, reg_val);
}
if(ret){
printk("*** GPIO_DIR_OUTPUT: Complete fail writing OUTPUT register");
dev_err(&chip->client->dev, "failed writing register\n");
return ret;
}

chip->reg_output = reg_val;

/* then direction */
reg_val = chip->reg_direction & ~(1u << off);
ret = pca953x_write_reg(chip, PCA953X_DIRECTION, reg_val);
if (ret)
return ret;

if(chip->reset_pin_number){ // if reset pin exists, attempt to reset
printk("*** GPIO_DIR_OUTPUT: fail writing DIR register INIT - RESETTING...\n\r");
ret = pca953x_reset(chip);
if(ret == -RESET_SETPIN_FAIL){
printk("*** GPIO_DIR_OUTPUT: fail setting reset pin post write DIR reg fail\n\r");
dev_err(&chip->client->dev, "failed setting reset pin\n");
return ret;
}
ret = pca953x_write_reg(chip, PCA953X_DIRECTION, reg_val);
}
if(ret){
printk("*** GPIO_DIR_OUTPUT: Complete fail writing DIRECTION register");
dev_err(&chip->client->dev, "failed writing register\n");
return ret;
}
chip->reg_direction = reg_val;
printk("*** GPIO_DIR_OUTPUT: write_reg & [reset passed/not entered]; : OUTPUT reg_val %d\t DIR reg_val: %d\n\r", chip->reg_output, chip->reg_direction);
return 0;
}

Expand All @@ -149,12 +270,27 @@ static int pca953x_gpio_get_value(struct gpio_chip *gc, unsigned off)
* do unless gpio_*_value_cansleep() calls become different
* from their nonsleeping siblings (and report faults).
*/
return 0;
if(chip->reset_pin_number){ // if reset pin exists, attempt to reset
printk("*** GPIO_GET_VAL: fail reading INPUT register INIT - RESETTING...\n\r");
ret = pca953x_reset(chip);
if(ret == -RESET_SETPIN_FAIL){
printk("*** GPIO_GET_VAL: fail setting reset pin reg fail\n\r");
dev_err(&chip->client->dev, "failed setting reset pin\n");
return 0 ;
}
ret = pca953x_read_reg(chip, PCA953X_INPUT, &reg_val);
}
if(ret){
printk("*** GPIO_GET_VALUE: Complete fail reading INPUT register");
dev_err(&chip->client->dev, "failed reading register\n");
return 0;
}
}

printk("*** GPIO_GET_VAL: read_reg & [reset passed/not entered]; ret: %d\t reg_val: %d\n\r", ret, reg_val);
return (reg_val & (1u << off)) ? 1 : 0;
}

// return type void. reset fail is handled by dev_err and return
static void pca953x_gpio_set_value(struct gpio_chip *gc, unsigned off, int val)
{
struct pca953x_chip *chip;
Expand All @@ -167,12 +303,26 @@ static void pca953x_gpio_set_value(struct gpio_chip *gc, unsigned off, int val)
reg_val = chip->reg_output | (1u << off);
else
reg_val = chip->reg_output & ~(1u << off);

ret = pca953x_write_reg(chip, PCA953X_OUTPUT, reg_val);
if (ret)
return;

chip->reg_output = reg_val;
// if write fails, attempt to reset and write again
if (ret){
if(chip->reset_pin_number){ // if reset pin exists, attempt to reset
ret = pca953x_reset(chip);
if(ret == -RESET_SETPIN_FAIL){
dev_err(&chip->client->dev, "failed setting reset pin\n");
printk("*** GPIO_SET_VAL: reset failed pca953x \n\r");
return;
}
ret = pca953x_write_reg(chip, PCA953X_OUTPUT, reg_val);
}
if(ret){
dev_err(&chip->client->dev, "failed writing register\n");
printk("*** GPIO_SET_VAL: write reg failed pca953x \n\r");
return;
}
}
chip->reg_output = reg_val; // only update cache if write successful
printk("*** GPIO_SET_VAL: write_reg & [reset passed/not entered]; : OUTPUT reg_val: %u\n\r", reg_val);
}

static void pca953x_setup_gpio(struct pca953x_chip *chip, int gpios)
Expand Down Expand Up @@ -212,14 +362,20 @@ static int __devinit pca953x_probe(struct i2c_client *client,
return -ENOMEM;

chip->client = client;

chip->reset_pin_number = pdata->reset_pin_number;
chip->gpio_start = pdata->gpio_base;
chip->reg_invert = pdata->invert;

/* initialize cached registers from their original values.
* we can't share this chip with another i2c master.
*/
pca953x_setup_gpio(chip, id->driver_data);

if(strncmp(id->name, "pi4ioe5v9539", 12) != 0){
// this is NOT a resettable gpio expander, hard set reset_pin_number = 0 (safety)
chip->reset_pin_number = 0;
}

ret = pca953x_read_reg(chip, PCA953X_OUTPUT, &chip->reg_output);
if (ret) {
printk("*** read output failed pca\n\r");
Expand Down Expand Up @@ -253,12 +409,13 @@ static int __devinit pca953x_probe(struct i2c_client *client,
}

i2c_set_clientdata(client, chip);
printk("***** pca953x probe successful ****");
return 0;

out_failed:
printk("*** out failed pca953x \n\r");
kfree(chip);
return ret;
out_failed:
printk("*** out failed pca953x \n\r");
kfree(chip);
return ret;
}

static int pca953x_remove(struct i2c_client *client)
Expand All @@ -283,7 +440,6 @@ static int pca953x_remove(struct i2c_client *client)
"gpiochip_remove()", ret);
return ret;
}

kfree(chip);
return 0;
}
Expand Down
6 changes: 4 additions & 2 deletions include/linux/i2c/pca953x.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,12 +5,14 @@
struct pca953x_platform_data {
/* number of the first GPIO */
unsigned gpio_base;

/* initial polarity inversion setting */
uint16_t invert;

void *context; /* param to setup/teardown */

/* accounting for reset pin on pi4ioe5 specific commander*/
uint32_t reset_pin_number;

int (*setup)(struct i2c_client *client,
unsigned gpio, unsigned ngpio,
void *context);
Expand Down