The RTL8231 is implemented as an MDIO device, and provides a regmap
interface for register access by the core and child devices.
The chip can also be a device on an SMI bus, an I2C-like bus by Realtek.
Since kernel support for SMI is limited, and no real-world SMI
implementations have been encountered for this device, this is currently
unimplemented. The use of the regmap interface should make any future
support relatively straightforward.
After a soft reset, all pins are muxed to GPIO inputs before the pin
drivers are enabled. This is done to prevent accidental system resets,
when a pin is connected to the main SoC's reset line.
Signed-off-by: Sander Vanheule <sander@svanheule.net>
---
drivers/mfd/Kconfig | 9 ++
drivers/mfd/Makefile | 1 +
drivers/mfd/rtl8231.c | 193 ++++++++++++++++++++++++++++++++++++
include/linux/mfd/rtl8231.h | 71 +++++++++++++
4 files changed, 274 insertions(+)
create mode 100644 drivers/mfd/rtl8231.c
create mode 100644 include/linux/mfd/rtl8231.h
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 6cec1858947b..e13e2df63fee 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1301,6 +1301,15 @@ config MFD_RDC321X
southbridge which provides access to GPIOs and Watchdog using the
southbridge PCI device configuration space.
+config MFD_RTL8231
+ tristate "Realtek RTL8231 GPIO and LED expander"
+ select MFD_CORE
+ select REGMAP_MDIO
+ help
+ Support for the Realtek RTL8231 GPIO and LED expander.
+ Provides up to 37 GPIOs, 88 LEDs, and one PWM output.
+ When built as a module, this module will be named rtl8231.
+
config MFD_RT4831
tristate "Richtek RT4831 four channel WLED and Display Bias Voltage"
depends on I2C
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 865e9f12faff..ba973382a20f 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -252,6 +252,7 @@ obj-$(CONFIG_MFD_HI6421_PMIC) += hi6421-pmic-core.o
obj-$(CONFIG_MFD_HI6421_SPMI) += hi6421-spmi-pmic.o
obj-$(CONFIG_MFD_HI655X_PMIC) += hi655x-pmic.o
obj-$(CONFIG_MFD_DLN2) += dln2.o
+obj-$(CONFIG_MFD_RTL8231) += rtl8231.o
obj-$(CONFIG_MFD_RT4831) += rt4831.o
obj-$(CONFIG_MFD_RT5033) += rt5033.o
obj-$(CONFIG_MFD_RT5120) += rt5120.o
diff --git a/drivers/mfd/rtl8231.c b/drivers/mfd/rtl8231.c
new file mode 100644
index 000000000000..60d4a0feea5c
--- /dev/null
+++ b/drivers/mfd/rtl8231.c
@@ -0,0 +1,193 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bits.h>
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/mfd/core.h>
+#include <linux/mdio.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#include <linux/mfd/rtl8231.h>
+
+static bool rtl8231_volatile_reg(struct device *dev, unsigned int reg)
+{
+ switch (reg) {
+ /*
+ * Registers with self-clearing bits, strapping pin values.
+ * Don't mark the data registers as volatile, since we need
+ * caching for the output values.
+ */
+ case RTL8231_REG_FUNC0:
+ case RTL8231_REG_FUNC1:
+ case RTL8231_REG_PIN_HI_CFG:
+ case RTL8231_REG_LED_END:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static const struct reg_field RTL8231_FIELD_LED_START = REG_FIELD(RTL8231_REG_FUNC0, 1, 1);
+
+static const struct mfd_cell rtl8231_cells[] = {
+ {
+ .name = "rtl8231-pinctrl",
+ },
+ {
+ .name = "rtl8231-leds",
+ .of_compatible = "realtek,rtl8231-leds",
+ },
+};
+
+static int rtl8231_soft_reset(struct regmap *map)
+{
+ const unsigned int all_pins_mask = GENMASK(RTL8231_BITS_VAL - 1, 0);
+ unsigned int val;
+ int err;
+
+ /* SOFT_RESET bit self-clears when done */
+ regmap_write_bits(map, RTL8231_REG_PIN_HI_CFG,
+ RTL8231_PIN_HI_CFG_SOFT_RESET, RTL8231_PIN_HI_CFG_SOFT_RESET);
+ err = regmap_read_poll_timeout(map, RTL8231_REG_PIN_HI_CFG, val,
+ !(val & RTL8231_PIN_HI_CFG_SOFT_RESET), 50, 1000);
+ if (err)
+ return err;
+
+ regcache_mark_dirty(map);
+
+ /*
+ * Chip reset results in a pin configuration that is a mix of LED and GPIO outputs.
+ * Select GPI functionality for all pins before enabling pin outputs.
+ */
+ regmap_write(map, RTL8231_REG_PIN_MODE0, all_pins_mask);
+ regmap_write(map, RTL8231_REG_GPIO_DIR0, all_pins_mask);
+ regmap_write(map, RTL8231_REG_PIN_MODE1, all_pins_mask);
+ regmap_write(map, RTL8231_REG_GPIO_DIR1, all_pins_mask);
+ regmap_write(map, RTL8231_REG_PIN_HI_CFG,
+ RTL8231_PIN_HI_CFG_MODE_MASK | RTL8231_PIN_HI_CFG_DIR_MASK);
+
+ return 0;
+}
+
+static int rtl8231_init(struct device *dev, struct regmap *map)
+{
+ struct regmap_field *led_start;
+ unsigned int started;
+ unsigned int val;
+ int err;
+
+ err = regmap_read(map, RTL8231_REG_FUNC1, &val);
+ if (err) {
+ dev_err(dev, "failed to read READY_CODE\n");
+ return err;
+ }
+
+ val = FIELD_GET(RTL8231_FUNC1_READY_CODE_MASK, val);
+ if (val != RTL8231_FUNC1_READY_CODE_VALUE) {
+ dev_err(dev, "RTL8231 not present or ready 0x%x != 0x%x\n",
+ val, RTL8231_FUNC1_READY_CODE_VALUE);
+ return -ENODEV;
+ }
+
+ led_start = dev_get_drvdata(dev);
+ err = regmap_field_read(led_start, &started);
+ if (err)
+ return err;
+
+ if (!started) {
+ err = rtl8231_soft_reset(map);
+ if (err)
+ return err;
+ /* LED_START enables power to output pins, and starts the LED engine */
+ err = regmap_field_force_write(led_start, 1);
+ }
+
+ return err;
+}
+
+static const struct regmap_config rtl8231_mdio_regmap_config = {
+ .val_bits = RTL8231_BITS_VAL,
+ .reg_bits = RTL8231_BITS_REG,
+ .volatile_reg = rtl8231_volatile_reg,
+ .max_register = RTL8231_REG_COUNT - 1,
+ .use_single_read = true,
+ .use_single_write = true,
+ .reg_format_endian = REGMAP_ENDIAN_BIG,
+ .val_format_endian = REGMAP_ENDIAN_BIG,
+ /* Cannot use REGCACHE_FLAT because it's not smart enough about cache invalidation */
+ .cache_type = REGCACHE_MAPLE,
+};
+
+static int rtl8231_mdio_probe(struct mdio_device *mdiodev)
+{
+ struct device *dev = &mdiodev->dev;
+ struct regmap_field *led_start;
+ struct regmap *map;
+ int err;
+
+ map = devm_regmap_init_mdio(mdiodev, &rtl8231_mdio_regmap_config);
+ if (IS_ERR(map)) {
+ dev_err(dev, "failed to init regmap\n");
+ return PTR_ERR(map);
+ }
+
+ led_start = devm_regmap_field_alloc(dev, map, RTL8231_FIELD_LED_START);
+ if (IS_ERR(led_start))
+ return PTR_ERR(led_start);
+
+ dev_set_drvdata(dev, led_start);
+
+ mdiodev->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+ if (IS_ERR(mdiodev->reset_gpio))
+ return PTR_ERR(mdiodev->reset_gpio);
+
+ device_property_read_u32(dev, "reset-assert-delay", &mdiodev->reset_assert_delay);
+ device_property_read_u32(dev, "reset-deassert-delay", &mdiodev->reset_deassert_delay);
+
+ err = rtl8231_init(dev, map);
+ if (err)
+ return err;
+
+ return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO, rtl8231_cells,
+ ARRAY_SIZE(rtl8231_cells), NULL, 0, NULL);
+}
+
+__maybe_unused static int rtl8231_suspend(struct device *dev)
+{
+ struct regmap_field *led_start = dev_get_drvdata(dev);
+
+ return regmap_field_force_write(led_start, 0);
+}
+
+__maybe_unused static int rtl8231_resume(struct device *dev)
+{
+ struct regmap_field *led_start = dev_get_drvdata(dev);
+
+ return regmap_field_force_write(led_start, 1);
+}
+
+static SIMPLE_DEV_PM_OPS(rtl8231_pm_ops, rtl8231_suspend, rtl8231_resume);
+
+static const struct of_device_id rtl8231_of_match[] = {
+ { .compatible = "realtek,rtl8231" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, rtl8231_of_match);
+
+static struct mdio_driver rtl8231_mdio_driver = {
+ .mdiodrv.driver = {
+ .name = "rtl8231-expander",
+ .of_match_table = rtl8231_of_match,
+ .pm = pm_ptr(&rtl8231_pm_ops),
+ },
+ .probe = rtl8231_mdio_probe,
+};
+mdio_module_driver(rtl8231_mdio_driver);
+
+MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
+MODULE_DESCRIPTION("Realtek RTL8231 GPIO and LED expander");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/mfd/rtl8231.h b/include/linux/mfd/rtl8231.h
new file mode 100644
index 000000000000..003eda3797a3
--- /dev/null
+++ b/include/linux/mfd/rtl8231.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Register definitions the RTL8231 GPIO and LED expander chip
+ */
+
+#ifndef __LINUX_MFD_RTL8231_H
+#define __LINUX_MFD_RTL8231_H
+
+#include <linux/bits.h>
+
+/*
+ * Registers addresses are 5 bit, values are 16 bit
+ * Also define a duplicated range of virtual addresses, to enable
+ * different read/write behaviour on the GPIO data registers
+ */
+#define RTL8231_BITS_VAL 16
+#define RTL8231_BITS_REG 5
+
+/* Chip control */
+#define RTL8231_REG_FUNC0 0x00
+#define RTL8231_FUNC0_SCAN_MODE BIT(0)
+#define RTL8231_FUNC0_SCAN_SINGLE 0
+#define RTL8231_FUNC0_SCAN_BICOLOR BIT(0)
+
+#define RTL8231_REG_FUNC1 0x01
+#define RTL8231_FUNC1_READY_CODE_VALUE 0x37
+#define RTL8231_FUNC1_READY_CODE_MASK GENMASK(9, 4)
+#define RTL8231_FUNC1_DEBOUNCE_MASK GENMASK(15, 10)
+
+/* Pin control */
+#define RTL8231_REG_PIN_MODE0 0x02
+#define RTL8231_REG_PIN_MODE1 0x03
+
+#define RTL8231_PIN_MODE_LED 0
+#define RTL8231_PIN_MODE_GPIO 1
+
+/* Pin high config: pin and GPIO control for pins 32-26 */
+#define RTL8231_REG_PIN_HI_CFG 0x04
+#define RTL8231_PIN_HI_CFG_MODE_MASK GENMASK(4, 0)
+#define RTL8231_PIN_HI_CFG_DIR_MASK GENMASK(9, 5)
+#define RTL8231_PIN_HI_CFG_INV_MASK GENMASK(14, 10)
+#define RTL8231_PIN_HI_CFG_SOFT_RESET BIT(15)
+
+/* GPIO control registers */
+#define RTL8231_REG_GPIO_DIR0 0x05
+#define RTL8231_REG_GPIO_DIR1 0x06
+#define RTL8231_REG_GPIO_INVERT0 0x07
+#define RTL8231_REG_GPIO_INVERT1 0x08
+
+#define RTL8231_GPIO_DIR_IN 1
+#define RTL8231_GPIO_DIR_OUT 0
+
+/*
+ * GPIO data registers
+ * Only the output data can be written to these registers, and only the input
+ * data can be read.
+ */
+#define RTL8231_REG_GPIO_DATA0 0x1c
+#define RTL8231_REG_GPIO_DATA1 0x1d
+#define RTL8231_REG_GPIO_DATA2 0x1e
+#define RTL8231_PIN_HI_DATA_MASK GENMASK(4, 0)
+
+/* LED control base registers */
+#define RTL8231_REG_LED0_BASE 0x09
+#define RTL8231_REG_LED1_BASE 0x10
+#define RTL8231_REG_LED2_BASE 0x17
+#define RTL8231_REG_LED_END 0x1b
+
+#define RTL8231_REG_COUNT 0x1f
+
+#endif /* __LINUX_MFD_RTL8231_H */
--
2.51.0On Tue, 21 Oct 2025, Sander Vanheule wrote:
> The RTL8231 is implemented as an MDIO device, and provides a regmap
> interface for register access by the core and child devices.
>
> The chip can also be a device on an SMI bus, an I2C-like bus by Realtek.
> Since kernel support for SMI is limited, and no real-world SMI
> implementations have been encountered for this device, this is currently
> unimplemented. The use of the regmap interface should make any future
> support relatively straightforward.
>
> After a soft reset, all pins are muxed to GPIO inputs before the pin
> drivers are enabled. This is done to prevent accidental system resets,
> when a pin is connected to the main SoC's reset line.
>
> Signed-off-by: Sander Vanheule <sander@svanheule.net>
> ---
> drivers/mfd/Kconfig | 9 ++
> drivers/mfd/Makefile | 1 +
> drivers/mfd/rtl8231.c | 193 ++++++++++++++++++++++++++++++++++++
> include/linux/mfd/rtl8231.h | 71 +++++++++++++
> 4 files changed, 274 insertions(+)
> create mode 100644 drivers/mfd/rtl8231.c
> create mode 100644 include/linux/mfd/rtl8231.h
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 6cec1858947b..e13e2df63fee 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1301,6 +1301,15 @@ config MFD_RDC321X
> southbridge which provides access to GPIOs and Watchdog using the
> southbridge PCI device configuration space.
>
> +config MFD_RTL8231
> + tristate "Realtek RTL8231 GPIO and LED expander"
> + select MFD_CORE
> + select REGMAP_MDIO
> + help
> + Support for the Realtek RTL8231 GPIO and LED expander.
> + Provides up to 37 GPIOs, 88 LEDs, and one PWM output.
> + When built as a module, this module will be named rtl8231.
> +
> config MFD_RT4831
> tristate "Richtek RT4831 four channel WLED and Display Bias Voltage"
> depends on I2C
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 865e9f12faff..ba973382a20f 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -252,6 +252,7 @@ obj-$(CONFIG_MFD_HI6421_PMIC) += hi6421-pmic-core.o
> obj-$(CONFIG_MFD_HI6421_SPMI) += hi6421-spmi-pmic.o
> obj-$(CONFIG_MFD_HI655X_PMIC) += hi655x-pmic.o
> obj-$(CONFIG_MFD_DLN2) += dln2.o
> +obj-$(CONFIG_MFD_RTL8231) += rtl8231.o
> obj-$(CONFIG_MFD_RT4831) += rt4831.o
> obj-$(CONFIG_MFD_RT5033) += rt5033.o
> obj-$(CONFIG_MFD_RT5120) += rt5120.o
> diff --git a/drivers/mfd/rtl8231.c b/drivers/mfd/rtl8231.c
> new file mode 100644
> index 000000000000..60d4a0feea5c
> --- /dev/null
> +++ b/drivers/mfd/rtl8231.c
> @@ -0,0 +1,193 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <linux/bits.h>
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mdio.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
Alphabetical please.
> +#include <linux/mfd/rtl8231.h>
> +
> +static bool rtl8231_volatile_reg(struct device *dev, unsigned int reg)
> +{
> + switch (reg) {
> + /*
> + * Registers with self-clearing bits, strapping pin values.
> + * Don't mark the data registers as volatile, since we need
> + * caching for the output values.
> + */
> + case RTL8231_REG_FUNC0:
> + case RTL8231_REG_FUNC1:
> + case RTL8231_REG_PIN_HI_CFG:
> + case RTL8231_REG_LED_END:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> +static const struct reg_field RTL8231_FIELD_LED_START = REG_FIELD(RTL8231_REG_FUNC0, 1, 1);
Why does this have to be global?
Variables should be lowercase.
> +static const struct mfd_cell rtl8231_cells[] = {
> + {
> + .name = "rtl8231-pinctrl",
> + },
> + {
> + .name = "rtl8231-leds",
> + .of_compatible = "realtek,rtl8231-leds",
> + },
> +};
This is a pretty tenuous MFD!
> +static int rtl8231_soft_reset(struct regmap *map)
s/map/regmap/
> +{
> + const unsigned int all_pins_mask = GENMASK(RTL8231_BITS_VAL - 1, 0);
> + unsigned int val;
> + int err;
> +
> + /* SOFT_RESET bit self-clears when done */
> + regmap_write_bits(map, RTL8231_REG_PIN_HI_CFG,
> + RTL8231_PIN_HI_CFG_SOFT_RESET, RTL8231_PIN_HI_CFG_SOFT_RESET);
> + err = regmap_read_poll_timeout(map, RTL8231_REG_PIN_HI_CFG, val,
> + !(val & RTL8231_PIN_HI_CFG_SOFT_RESET), 50, 1000);
> + if (err)
> + return err;
Do we have to scrunch these calls together?
> + regcache_mark_dirty(map);
> +
> + /*
> + * Chip reset results in a pin configuration that is a mix of LED and GPIO outputs.
> + * Select GPI functionality for all pins before enabling pin outputs.
> + */
> + regmap_write(map, RTL8231_REG_PIN_MODE0, all_pins_mask);
> + regmap_write(map, RTL8231_REG_GPIO_DIR0, all_pins_mask);
> + regmap_write(map, RTL8231_REG_PIN_MODE1, all_pins_mask);
> + regmap_write(map, RTL8231_REG_GPIO_DIR1, all_pins_mask);
> + regmap_write(map, RTL8231_REG_PIN_HI_CFG,
> + RTL8231_PIN_HI_CFG_MODE_MASK | RTL8231_PIN_HI_CFG_DIR_MASK);
> +
> + return 0;
> +}
> +
> +static int rtl8231_init(struct device *dev, struct regmap *map)
> +{
> + struct regmap_field *led_start;
> + unsigned int started;
> + unsigned int val;
If this is used for only one thing, it makes sense to use better
nomenclature that refers to that thing.
> + int err;
> +
> + err = regmap_read(map, RTL8231_REG_FUNC1, &val);
> + if (err) {
> + dev_err(dev, "failed to read READY_CODE\n");
> + return err;
> + }
> +
> + val = FIELD_GET(RTL8231_FUNC1_READY_CODE_MASK, val);
> + if (val != RTL8231_FUNC1_READY_CODE_VALUE) {
> + dev_err(dev, "RTL8231 not present or ready 0x%x != 0x%x\n",
> + val, RTL8231_FUNC1_READY_CODE_VALUE);
> + return -ENODEV;
> + }
> +
> + led_start = dev_get_drvdata(dev);
> + err = regmap_field_read(led_start, &started);
> + if (err)
> + return err;
> +
> + if (!started) {
Reverse the logic and exit early if 'started'.
> + err = rtl8231_soft_reset(map);
> + if (err)
> + return err;
'\n' here.
> + /* LED_START enables power to output pins, and starts the LED engine */
> + err = regmap_field_force_write(led_start, 1);
> + }
> +
> + return err;
> +}
> +
> +static const struct regmap_config rtl8231_mdio_regmap_config = {
> + .val_bits = RTL8231_BITS_VAL,
> + .reg_bits = RTL8231_BITS_REG,
> + .volatile_reg = rtl8231_volatile_reg,
> + .max_register = RTL8231_REG_COUNT - 1,
> + .use_single_read = true,
> + .use_single_write = true,
> + .reg_format_endian = REGMAP_ENDIAN_BIG,
> + .val_format_endian = REGMAP_ENDIAN_BIG,
> + /* Cannot use REGCACHE_FLAT because it's not smart enough about cache invalidation */
> + .cache_type = REGCACHE_MAPLE,
> +};
> +
> +static int rtl8231_mdio_probe(struct mdio_device *mdiodev)
> +{
> + struct device *dev = &mdiodev->dev;
> + struct regmap_field *led_start;
> + struct regmap *map;
> + int err;
> +
> + map = devm_regmap_init_mdio(mdiodev, &rtl8231_mdio_regmap_config);
> + if (IS_ERR(map)) {
> + dev_err(dev, "failed to init regmap\n");
> + return PTR_ERR(map);
> + }
> +
> + led_start = devm_regmap_field_alloc(dev, map, RTL8231_FIELD_LED_START);
> + if (IS_ERR(led_start))
> + return PTR_ERR(led_start);
Why do we need to do LED specific actions in the core driver?
> + dev_set_drvdata(dev, led_start);
> +
> + mdiodev->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> + if (IS_ERR(mdiodev->reset_gpio))
> + return PTR_ERR(mdiodev->reset_gpio);
> +
> + device_property_read_u32(dev, "reset-assert-delay", &mdiodev->reset_assert_delay);
> + device_property_read_u32(dev, "reset-deassert-delay", &mdiodev->reset_deassert_delay);
> +
> + err = rtl8231_init(dev, map);
> + if (err)
> + return err;
> +
> + return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO, rtl8231_cells,
> + ARRAY_SIZE(rtl8231_cells), NULL, 0, NULL);
Odd tabbing. Please line-up with the '(' like usual.
> +}
> +
> +__maybe_unused static int rtl8231_suspend(struct device *dev)
The __maybe_unused comes after the "static int" part.
> +{
> + struct regmap_field *led_start = dev_get_drvdata(dev);
> +
> + return regmap_field_force_write(led_start, 0);
> +}
> +
> +__maybe_unused static int rtl8231_resume(struct device *dev)
> +{
> + struct regmap_field *led_start = dev_get_drvdata(dev);
> +
> + return regmap_field_force_write(led_start, 1);
> +}
> +
> +static SIMPLE_DEV_PM_OPS(rtl8231_pm_ops, rtl8231_suspend, rtl8231_resume);
> +
> +static const struct of_device_id rtl8231_of_match[] = {
> + { .compatible = "realtek,rtl8231" },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, rtl8231_of_match);
> +
> +static struct mdio_driver rtl8231_mdio_driver = {
> + .mdiodrv.driver = {
> + .name = "rtl8231-expander",
> + .of_match_table = rtl8231_of_match,
> + .pm = pm_ptr(&rtl8231_pm_ops),
> + },
> + .probe = rtl8231_mdio_probe,
> +};
> +mdio_module_driver(rtl8231_mdio_driver);
> +
> +MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
> +MODULE_DESCRIPTION("Realtek RTL8231 GPIO and LED expander");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/mfd/rtl8231.h b/include/linux/mfd/rtl8231.h
> new file mode 100644
> index 000000000000..003eda3797a3
> --- /dev/null
> +++ b/include/linux/mfd/rtl8231.h
> @@ -0,0 +1,71 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Register definitions the RTL8231 GPIO and LED expander chip
> + */
> +
> +#ifndef __LINUX_MFD_RTL8231_H
> +#define __LINUX_MFD_RTL8231_H
> +
> +#include <linux/bits.h>
> +
> +/*
> + * Registers addresses are 5 bit, values are 16 bit
> + * Also define a duplicated range of virtual addresses, to enable
> + * different read/write behaviour on the GPIO data registers
> + */
> +#define RTL8231_BITS_VAL 16
> +#define RTL8231_BITS_REG 5
> +
> +/* Chip control */
> +#define RTL8231_REG_FUNC0 0x00
> +#define RTL8231_FUNC0_SCAN_MODE BIT(0)
> +#define RTL8231_FUNC0_SCAN_SINGLE 0
> +#define RTL8231_FUNC0_SCAN_BICOLOR BIT(0)
> +
> +#define RTL8231_REG_FUNC1 0x01
> +#define RTL8231_FUNC1_READY_CODE_VALUE 0x37
> +#define RTL8231_FUNC1_READY_CODE_MASK GENMASK(9, 4)
> +#define RTL8231_FUNC1_DEBOUNCE_MASK GENMASK(15, 10)
> +
> +/* Pin control */
> +#define RTL8231_REG_PIN_MODE0 0x02
> +#define RTL8231_REG_PIN_MODE1 0x03
> +
> +#define RTL8231_PIN_MODE_LED 0
> +#define RTL8231_PIN_MODE_GPIO 1
> +
> +/* Pin high config: pin and GPIO control for pins 32-26 */
> +#define RTL8231_REG_PIN_HI_CFG 0x04
> +#define RTL8231_PIN_HI_CFG_MODE_MASK GENMASK(4, 0)
> +#define RTL8231_PIN_HI_CFG_DIR_MASK GENMASK(9, 5)
> +#define RTL8231_PIN_HI_CFG_INV_MASK GENMASK(14, 10)
> +#define RTL8231_PIN_HI_CFG_SOFT_RESET BIT(15)
> +
> +/* GPIO control registers */
> +#define RTL8231_REG_GPIO_DIR0 0x05
> +#define RTL8231_REG_GPIO_DIR1 0x06
> +#define RTL8231_REG_GPIO_INVERT0 0x07
> +#define RTL8231_REG_GPIO_INVERT1 0x08
> +
> +#define RTL8231_GPIO_DIR_IN 1
> +#define RTL8231_GPIO_DIR_OUT 0
> +
> +/*
> + * GPIO data registers
> + * Only the output data can be written to these registers, and only the input
> + * data can be read.
> + */
> +#define RTL8231_REG_GPIO_DATA0 0x1c
> +#define RTL8231_REG_GPIO_DATA1 0x1d
> +#define RTL8231_REG_GPIO_DATA2 0x1e
> +#define RTL8231_PIN_HI_DATA_MASK GENMASK(4, 0)
> +
> +/* LED control base registers */
> +#define RTL8231_REG_LED0_BASE 0x09
> +#define RTL8231_REG_LED1_BASE 0x10
> +#define RTL8231_REG_LED2_BASE 0x17
> +#define RTL8231_REG_LED_END 0x1b
> +
> +#define RTL8231_REG_COUNT 0x1f
> +
> +#endif /* __LINUX_MFD_RTL8231_H */
> --
> 2.51.0
>
>
--
Lee Jones [李琼斯]
Hi Lee,
On Thu, 2025-11-06 at 16:33 +0000, Lee Jones wrote:
> On Tue, 21 Oct 2025, Sander Vanheule wrote:
> > @@ -0,0 +1,193 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +
> > +#include <linux/bits.h>
> > +#include <linux/bitfield.h>
> > +#include <linux/delay.h>
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/mfd/core.h>
> > +#include <linux/mdio.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/property.h>
> > +#include <linux/regmap.h>
>
> Alphabetical please.
Ack
> > +static const struct reg_field RTL8231_FIELD_LED_START =
> > REG_FIELD(RTL8231_REG_FUNC0, 1, 1);
>
> Why does this have to be global?
>
> Variables should be lowercase.
Moving it to the one place where it's used.
> > +static const struct mfd_cell rtl8231_cells[] = {
> > + {
> > + .name = "rtl8231-pinctrl",
> > + },
> > + {
> > + .name = "rtl8231-leds",
> > + .of_compatible = "realtek,rtl8231-leds",
> > + },
> > +};
>
> This is a pretty tenuous MFD!
I suppose two functions is the minimum to count as multi-functional :-)
I need a place to perform chip detection and to start the output drivers. The
latter could be part of a pinctrl driver, but making the led driver depend on
the pinctrl driver doesn't sit too well with me. Now the functionality is
cleanly split across the MFD core driver and pinctrl/led drivers.
> > +static int rtl8231_soft_reset(struct regmap *map)
>
> s/map/regmap/
Ack, replaced throughout the driver.
> > +{
> > + const unsigned int all_pins_mask = GENMASK(RTL8231_BITS_VAL - 1,
> > 0);
> > + unsigned int val;
> > + int err;
> > +
> > + /* SOFT_RESET bit self-clears when done */
> > + regmap_write_bits(map, RTL8231_REG_PIN_HI_CFG,
> > + RTL8231_PIN_HI_CFG_SOFT_RESET,
> > RTL8231_PIN_HI_CFG_SOFT_RESET);
> > + err = regmap_read_poll_timeout(map, RTL8231_REG_PIN_HI_CFG, val,
> > + !(val & RTL8231_PIN_HI_CFG_SOFT_RESET), 50, 1000);
> > + if (err)
> > + return err;
>
> Do we have to scrunch these calls together?
Made it a bit less claustrophobic.
> > + regcache_mark_dirty(map);
This marks the device register state as invalid, which isn't what I wanted here.
After a reset, the cache should be repopulated, so this is now:
regcache_drop_region(0, RTL8231_REG_COUNT - 1);
> > +static int rtl8231_init(struct device *dev, struct regmap *map)
> > +{
> > + struct regmap_field *led_start;
> > + unsigned int started;
> > + unsigned int val;
>
> If this is used for only one thing, it makes sense to use better
> nomenclature that refers to that thing.
Ack, updated the naming a bit.
> > + led_start = dev_get_drvdata(dev);
> > + err = regmap_field_read(led_start, &started);
> > + if (err)
> > + return err;
> > +
> > + if (!started) {
>
> Reverse the logic and exit early if 'started'.
Ack
>
> > + err = rtl8231_soft_reset(map);
> > + if (err)
> > + return err;
>
> '\n' here.
Ack
> > + /* LED_START enables power to output pins, and starts the
> > LED engine */
> > + err = regmap_field_force_write(led_start, 1);
This is in a volatile register, so the driver doesn't need to force anything to
write to the device and will now use regmap_field_write().
> > + led_start = devm_regmap_field_alloc(dev, map,
> > RTL8231_FIELD_LED_START);
> > + if (IS_ERR(led_start))
> > + return PTR_ERR(led_start);
>
> Why do we need to do LED specific actions in the core driver?
The is naming taken from the datasheet. Setting LED_START actually enables both
the LED scanning output engine and the output drivers. So this is needed for
proper functioning of the GPIO functionality too.
> > + return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
> > rtl8231_cells,
> > + ARRAY_SIZE(rtl8231_cells), NULL, 0, NULL);
>
> Odd tabbing. Please line-up with the '(' like usual.
Ack
> > +__maybe_unused static int rtl8231_suspend(struct device *dev)
>
> The __maybe_unused comes after the "static int" part.
Ack.
C11 attributes like [[maybe_unused]] must come before the "static int" part, but
that doesn't line up with how most of the kernel uses the attributes.
Best,
Sander
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