gpio: pca9570: add slg7xl45106 support

Dialog semiconductors SLG7XL45106 is an 8-bit I2C GPO expander.
The output port is controlled by a data byte with register
address. Add a compatible string for the same. Also update
the driver to write and read from it.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpio-pca9570.c

@@ -15,6 +15,8 @@
 #include <linux/mutex.h>
 #include <linux/property.h>
 
+#define SLG7XL45106_GPO_REG	0xDB
+
 /**
  * struct pca9570_platform_data - GPIO platformdata
  * @ngpio: no of gpios
@@ -44,7 +46,11 @@ static int pca9570_read(struct pca9570 *gpio, u8 *value)
 	struct i2c_client *client = to_i2c_client(gpio->chip.parent);
 	int ret;
 
+	if (gpio->p_data->command != 0)
+		ret = i2c_smbus_read_byte_data(client, gpio->p_data->command);
+	else
 		ret = i2c_smbus_read_byte(client);
+
 	if (ret < 0)
 		return ret;
 
@@ -56,6 +62,9 @@ static int pca9570_write(struct pca9570 *gpio, u8 value)
 {
 	struct i2c_client *client = to_i2c_client(gpio->chip.parent);
 
+	if (gpio->p_data->command != 0)
+		return i2c_smbus_write_byte_data(client, gpio->p_data->command, value);
+
 	return i2c_smbus_write_byte(client, value);
 }
 
@@ -140,14 +149,21 @@ static const struct pca9570_platform_data pca9571_gpio = {
 	.ngpio = 8,
 };
 
+static const struct pca9570_platform_data slg7xl45106_gpio = {
+	.ngpio = 8,
+	.command = SLG7XL45106_GPO_REG,
+};
+
 static const struct i2c_device_id pca9570_id_table[] = {
 	{ "pca9570", (kernel_ulong_t)&pca9570_gpio},
 	{ "pca9571", (kernel_ulong_t)&pca9571_gpio },
+	{ "slg7xl45106", (kernel_ulong_t)&slg7xl45106_gpio },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(i2c, pca9570_id_table);
 
 static const struct of_device_id pca9570_of_match_table[] = {
+	{ .compatible = "dlg,slg7xl45106", .data = &slg7xl45106_gpio},
 	{ .compatible = "nxp,pca9570", .data = &pca9570_gpio },
 	{ .compatible = "nxp,pca9571", .data = &pca9571_gpio },
 	{ /* sentinel */ }