platform: cznic: turris-omnia-mcu: Add support for MCU connected GPIOs

Add support for GPIOs connected to the MCU on the Turris Omnia board.

This includes:
- front button pin
- enable pins for USB regulators
- MiniPCIe / mSATA card presence pins in MiniPCIe port 0
- LED output pins from WAN ethernet PHY, LAN switch and MiniPCIe ports
- on board revisions 32+ also various peripheral resets and another
  voltage regulator enable pin
Signed-off-by: Marek Behún <kabel@kernel.org>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20240701113010.16447-4-kabel@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/ABI/testing/sysfs-bus-i2c-devices-turris-omnia-mcu

@@ -22,6 +22,22 @@ Description:	(RO) Contains device first MAC address. Each Turris Omnia is
 
 		Format: %pM.
 
+What:		/sys/bus/i2c/devices/<mcu_device>/front_button_mode
+Date:		September 2024
+KernelVersion:	6.11
+Contact:	Marek Behún <kabel@kernel.org>
+Description:	(RW) The front button on the Turris Omnia router can be
+		configured either to change the intensity of all the LEDs on the
+		front panel, or to send the press event to the CPU as an
+		interrupt.
+
+		This file switches between these two modes:
+		- "mcu" makes the button press event be handled by the MCU to
+		  change the LEDs panel intensity.
+		- "cpu" makes the button press event be handled by the CPU.
+
+		Format: %s.
+
 What:		/sys/bus/i2c/devices/<mcu_device>/fw_features
 Date:		September 2024
 KernelVersion:	6.11

drivers/platform/cznic/Kconfig

@@ -16,9 +16,24 @@ config TURRIS_OMNIA_MCU
 	tristate "Turris Omnia MCU driver"
 	depends on MACH_ARMADA_38X || COMPILE_TEST
 	depends on I2C
+	select GPIOLIB
+	select GPIOLIB_IRQCHIP
 	help
 	  Say Y here to add support for the features implemented by the
 	  microcontroller on the CZ.NIC's Turris Omnia SOHO router.
+	  The features include:
+	  - GPIO pins
+	    - to get front button press events (the front button can be
+	      configured either to generate press events to the CPU or to change
+	      front LEDs panel brightness)
+	    - to enable / disable USB port voltage regulators and to detect
+	      USB overcurrent
+	    - to detect MiniPCIe / mSATA card presence in MiniPCIe port 0
+	    - to configure resets of various peripherals on board revisions 32+
+	    - to enable / disable the VHV voltage regulator to the SOC in order
+	      to be able to program SOC's OTP on board revisions 32+
+	    - to get input from the LED output pins of the WAN ethernet PHY, LAN
+	      switch and MiniPCIe ports
 	  To compile this driver as a module, choose M here; the module will be
 	  called turris-omnia-mcu.
 

drivers/platform/cznic/Makefile

@@ -2,3 +2,4 @@
 
 obj-$(CONFIG_TURRIS_OMNIA_MCU)	+= turris-omnia-mcu.o
 turris-omnia-mcu-y		:= turris-omnia-mcu-base.o
+turris-omnia-mcu-y		+= turris-omnia-mcu-gpio.o

drivers/platform/cznic/turris-omnia-mcu-base.c

@@ -197,6 +197,7 @@ static const struct attribute_group omnia_mcu_base_group = {
 
 static const struct attribute_group *omnia_mcu_groups[] = {
 	&omnia_mcu_base_group,
+	&omnia_mcu_gpio_group,
 	NULL
 };
 
@@ -371,7 +372,7 @@ static int omnia_mcu_probe(struct i2c_client *client)
 					     "Cannot read board info\n");
 	}
 
-	return 0;
+	return omnia_mcu_register_gpiochip(mcu);
 }
 
 static const struct of_device_id of_omnia_mcu_match[] = {

drivers/platform/cznic/turris-omnia-mcu-gpio.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CZ.NIC's Turris Omnia MCU GPIO and IRQ driver
+ *
+ * 2024 by Marek Behún <kabel@kernel.org>
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/bug.h>
+#include <linux/cleanup.h>
+#include <linux/device.h>
+#include <linux/devm-helpers.h>
+#include <linux/errno.h>
+#include <linux/gpio/driver.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+#include <asm/unaligned.h>
+
+#include <linux/turris-omnia-mcu-interface.h>
+#include "turris-omnia-mcu.h"
+
+#define OMNIA_CMD_INT_ARG_LEN		8
+#define FRONT_BUTTON_RELEASE_DELAY_MS	50
+
+static const char * const omnia_mcu_gpio_templates[64] = {
+	/* GPIOs with value read from the 16-bit wide status */
+	[4]  = "MiniPCIe0 Card Detect",
+	[5]  = "MiniPCIe0 mSATA Indicator",
+	[6]  = "Front USB3 port over-current",
+	[7]  = "Rear USB3 port over-current",
+	[8]  = "Front USB3 port power",
+	[9]  = "Rear USB3 port power",
+	[12] = "Front Button",
+
+	/* GPIOs with value read from the 32-bit wide extended status */
+	[16] = "SFP nDET",
+	[28] = "MiniPCIe0 LED",
+	[29] = "MiniPCIe1 LED",
+	[30] = "MiniPCIe2 LED",
+	[31] = "MiniPCIe0 PAN LED",
+	[32] = "MiniPCIe1 PAN LED",
+	[33] = "MiniPCIe2 PAN LED",
+	[34] = "WAN PHY LED0",
+	[35] = "WAN PHY LED1",
+	[36] = "LAN switch p0 LED0",
+	[37] = "LAN switch p0 LED1",
+	[38] = "LAN switch p1 LED0",
+	[39] = "LAN switch p1 LED1",
+	[40] = "LAN switch p2 LED0",
+	[41] = "LAN switch p2 LED1",
+	[42] = "LAN switch p3 LED0",
+	[43] = "LAN switch p3 LED1",
+	[44] = "LAN switch p4 LED0",
+	[45] = "LAN switch p4 LED1",
+	[46] = "LAN switch p5 LED0",
+	[47] = "LAN switch p5 LED1",
+
+	/* GPIOs with value read from the 16-bit wide extended control status */
+	[48] = "eMMC nRESET",
+	[49] = "LAN switch nRESET",
+	[50] = "WAN PHY nRESET",
+	[51] = "MiniPCIe0 nPERST",
+	[52] = "MiniPCIe1 nPERST",
+	[53] = "MiniPCIe2 nPERST",
+	[54] = "WAN PHY SFP mux",
+	[56] = "VHV power disable",
+};
+
+struct omnia_gpio {
+	u8 cmd;
+	u8 ctl_cmd;
+	u8 bit;
+	u8 ctl_bit;
+	u8 int_bit;
+	u16 feat;
+	u16 feat_mask;
+};
+
+#define OMNIA_GPIO_INVALID_INT_BIT	0xff
+
+#define _DEF_GPIO(_cmd, _ctl_cmd, _bit, _ctl_bit, _int_bit, _feat, _feat_mask) \
+	{								\
+		.cmd = _cmd,						\
+		.ctl_cmd = _ctl_cmd,					\
+		.bit = _bit,						\
+		.ctl_bit = _ctl_bit,					\
+		.int_bit = (_int_bit) < 0 ? OMNIA_GPIO_INVALID_INT_BIT	\
+					  : (_int_bit),			\
+		.feat = _feat,						\
+		.feat_mask = _feat_mask,				\
+	}
+
+#define _DEF_GPIO_STS(_name) \
+	_DEF_GPIO(OMNIA_CMD_GET_STATUS_WORD, 0, __bf_shf(OMNIA_STS_ ## _name), \
+		  0, __bf_shf(OMNIA_INT_ ## _name), 0, 0)
+
+#define _DEF_GPIO_CTL(_name) \
+	_DEF_GPIO(OMNIA_CMD_GET_STATUS_WORD, OMNIA_CMD_GENERAL_CONTROL, \
+		  __bf_shf(OMNIA_STS_ ## _name), __bf_shf(OMNIA_CTL_ ## _name), \
+		  -1, 0, 0)
+
+#define _DEF_GPIO_EXT_STS(_name, _feat) \
+	_DEF_GPIO(OMNIA_CMD_GET_EXT_STATUS_DWORD, 0, \
+		  __bf_shf(OMNIA_EXT_STS_ ## _name), 0, \
+		  __bf_shf(OMNIA_INT_ ## _name), \
+		  OMNIA_FEAT_ ## _feat | OMNIA_FEAT_EXT_CMDS, \
+		  OMNIA_FEAT_ ## _feat | OMNIA_FEAT_EXT_CMDS)
+
+#define _DEF_GPIO_EXT_STS_LED(_name, _ledext) \
+	_DEF_GPIO(OMNIA_CMD_GET_EXT_STATUS_DWORD, 0, \
+		  __bf_shf(OMNIA_EXT_STS_ ## _name), 0, \
+		  __bf_shf(OMNIA_INT_ ## _name), \
+		  OMNIA_FEAT_LED_STATE_ ## _ledext, \
+		  OMNIA_FEAT_LED_STATE_EXT_MASK)
+
+#define _DEF_GPIO_EXT_STS_LEDALL(_name) \
+	_DEF_GPIO(OMNIA_CMD_GET_EXT_STATUS_DWORD, 0, \
+		  __bf_shf(OMNIA_EXT_STS_ ## _name), 0, \
+		  __bf_shf(OMNIA_INT_ ## _name), \
+		  OMNIA_FEAT_LED_STATE_EXT_MASK, 0)
+
+#define _DEF_GPIO_EXT_CTL(_name, _feat) \
+	_DEF_GPIO(OMNIA_CMD_GET_EXT_CONTROL_STATUS, OMNIA_CMD_EXT_CONTROL, \
+		  __bf_shf(OMNIA_EXT_CTL_ ## _name), \
+		  __bf_shf(OMNIA_EXT_CTL_ ## _name), -1, \
+		  OMNIA_FEAT_ ## _feat | OMNIA_FEAT_EXT_CMDS, \
+		  OMNIA_FEAT_ ## _feat | OMNIA_FEAT_EXT_CMDS)
+
+#define _DEF_INT(_name) \
+	_DEF_GPIO(0, 0, 0, 0, __bf_shf(OMNIA_INT_ ## _name), 0, 0)
+
+static inline bool is_int_bit_valid(const struct omnia_gpio *gpio)
+{
+	return gpio->int_bit != OMNIA_GPIO_INVALID_INT_BIT;
+}
+
+static const struct omnia_gpio omnia_gpios[64] = {
+	/* GPIOs with value read from the 16-bit wide status */
+	[4]  = _DEF_GPIO_STS(CARD_DET),
+	[5]  = _DEF_GPIO_STS(MSATA_IND),
+	[6]  = _DEF_GPIO_STS(USB30_OVC),
+	[7]  = _DEF_GPIO_STS(USB31_OVC),
+	[8]  = _DEF_GPIO_CTL(USB30_PWRON),
+	[9]  = _DEF_GPIO_CTL(USB31_PWRON),
+
+	/* brightness changed interrupt, no GPIO */
+	[11] = _DEF_INT(BRIGHTNESS_CHANGED),
+
+	[12] = _DEF_GPIO_STS(BUTTON_PRESSED),
+
+	/* TRNG interrupt, no GPIO */
+	[13] = _DEF_INT(TRNG),
+
+	/* MESSAGE_SIGNED interrupt, no GPIO */
+	[14] = _DEF_INT(MESSAGE_SIGNED),
+
+	/* GPIOs with value read from the 32-bit wide extended status */
+	[16] = _DEF_GPIO_EXT_STS(SFP_nDET, PERIPH_MCU),
+	[28] = _DEF_GPIO_EXT_STS_LEDALL(WLAN0_MSATA_LED),
+	[29] = _DEF_GPIO_EXT_STS_LEDALL(WLAN1_LED),
+	[30] = _DEF_GPIO_EXT_STS_LEDALL(WLAN2_LED),
+	[31] = _DEF_GPIO_EXT_STS_LED(WPAN0_LED, EXT),
+	[32] = _DEF_GPIO_EXT_STS_LED(WPAN1_LED, EXT),
+	[33] = _DEF_GPIO_EXT_STS_LED(WPAN2_LED, EXT),
+	[34] = _DEF_GPIO_EXT_STS_LEDALL(WAN_LED0),
+	[35] = _DEF_GPIO_EXT_STS_LED(WAN_LED1, EXT_V32),
+	[36] = _DEF_GPIO_EXT_STS_LEDALL(LAN0_LED0),
+	[37] = _DEF_GPIO_EXT_STS_LEDALL(LAN0_LED1),
+	[38] = _DEF_GPIO_EXT_STS_LEDALL(LAN1_LED0),
+	[39] = _DEF_GPIO_EXT_STS_LEDALL(LAN1_LED1),
+	[40] = _DEF_GPIO_EXT_STS_LEDALL(LAN2_LED0),
+	[41] = _DEF_GPIO_EXT_STS_LEDALL(LAN2_LED1),
+	[42] = _DEF_GPIO_EXT_STS_LEDALL(LAN3_LED0),
+	[43] = _DEF_GPIO_EXT_STS_LEDALL(LAN3_LED1),
+	[44] = _DEF_GPIO_EXT_STS_LEDALL(LAN4_LED0),
+	[45] = _DEF_GPIO_EXT_STS_LEDALL(LAN4_LED1),
+	[46] = _DEF_GPIO_EXT_STS_LEDALL(LAN5_LED0),
+	[47] = _DEF_GPIO_EXT_STS_LEDALL(LAN5_LED1),
+
+	/* GPIOs with value read from the 16-bit wide extended control status */
+	[48] = _DEF_GPIO_EXT_CTL(nRES_MMC, PERIPH_MCU),
+	[49] = _DEF_GPIO_EXT_CTL(nRES_LAN, PERIPH_MCU),
+	[50] = _DEF_GPIO_EXT_CTL(nRES_PHY, PERIPH_MCU),
+	[51] = _DEF_GPIO_EXT_CTL(nPERST0, PERIPH_MCU),
+	[52] = _DEF_GPIO_EXT_CTL(nPERST1, PERIPH_MCU),
+	[53] = _DEF_GPIO_EXT_CTL(nPERST2, PERIPH_MCU),
+	[54] = _DEF_GPIO_EXT_CTL(PHY_SFP, PERIPH_MCU),
+	[56] = _DEF_GPIO_EXT_CTL(nVHV_CTRL, PERIPH_MCU),
+};
+
+/* mapping from interrupts to indexes of GPIOs in the omnia_gpios array */
+static const u8 omnia_int_to_gpio_idx[32] = {
+	[__bf_shf(OMNIA_INT_CARD_DET)]			= 4,
+	[__bf_shf(OMNIA_INT_MSATA_IND)]			= 5,
+	[__bf_shf(OMNIA_INT_USB30_OVC)]			= 6,
+	[__bf_shf(OMNIA_INT_USB31_OVC)]			= 7,
+	[__bf_shf(OMNIA_INT_BUTTON_PRESSED)]		= 12,
+	[__bf_shf(OMNIA_INT_TRNG)]			= 13,
+	[__bf_shf(OMNIA_INT_MESSAGE_SIGNED)]		= 14,
+	[__bf_shf(OMNIA_INT_SFP_nDET)]			= 16,
+	[__bf_shf(OMNIA_INT_BRIGHTNESS_CHANGED)]	= 11,
+	[__bf_shf(OMNIA_INT_WLAN0_MSATA_LED)]		= 28,
+	[__bf_shf(OMNIA_INT_WLAN1_LED)]			= 29,
+	[__bf_shf(OMNIA_INT_WLAN2_LED)]			= 30,
+	[__bf_shf(OMNIA_INT_WPAN0_LED)]			= 31,
+	[__bf_shf(OMNIA_INT_WPAN1_LED)]			= 32,
+	[__bf_shf(OMNIA_INT_WPAN2_LED)]			= 33,
+	[__bf_shf(OMNIA_INT_WAN_LED0)]			= 34,
+	[__bf_shf(OMNIA_INT_WAN_LED1)]			= 35,
+	[__bf_shf(OMNIA_INT_LAN0_LED0)]			= 36,
+	[__bf_shf(OMNIA_INT_LAN0_LED1)]			= 37,
+	[__bf_shf(OMNIA_INT_LAN1_LED0)]			= 38,
+	[__bf_shf(OMNIA_INT_LAN1_LED1)]			= 39,
+	[__bf_shf(OMNIA_INT_LAN2_LED0)]			= 40,
+	[__bf_shf(OMNIA_INT_LAN2_LED1)]			= 41,
+	[__bf_shf(OMNIA_INT_LAN3_LED0)]			= 42,
+	[__bf_shf(OMNIA_INT_LAN3_LED1)]			= 43,
+	[__bf_shf(OMNIA_INT_LAN4_LED0)]			= 44,
+	[__bf_shf(OMNIA_INT_LAN4_LED1)]			= 45,
+	[__bf_shf(OMNIA_INT_LAN5_LED0)]			= 46,
+	[__bf_shf(OMNIA_INT_LAN5_LED1)]			= 47,
+};
+
+/* index of PHY_SFP GPIO in the omnia_gpios array */
+#define OMNIA_GPIO_PHY_SFP_OFFSET	54
+
+static int omnia_ctl_cmd_locked(struct omnia_mcu *mcu, u8 cmd, u16 val, u16 mask)
+{
+	unsigned int len;
+	u8 buf[5];
+
+	buf[0] = cmd;
+
+	switch (cmd) {
+	case OMNIA_CMD_GENERAL_CONTROL:
+		buf[1] = val;
+		buf[2] = mask;
+		len = 3;
+		break;
+
+	case OMNIA_CMD_EXT_CONTROL:
+		put_unaligned_le16(val, &buf[1]);
+		put_unaligned_le16(mask, &buf[3]);
+		len = 5;
+		break;
+
+	default:
+		BUG();
+	}
+
+	return omnia_cmd_write(mcu->client, buf, len);
+}
+
+static int omnia_ctl_cmd(struct omnia_mcu *mcu, u8 cmd, u16 val, u16 mask)
+{
+	guard(mutex)(&mcu->lock);
+
+	return omnia_ctl_cmd_locked(mcu, cmd, val, mask);
+}
+
+static int omnia_gpio_request(struct gpio_chip *gc, unsigned int offset)
+{
+	if (!omnia_gpios[offset].cmd)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int omnia_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+
+	if (offset == OMNIA_GPIO_PHY_SFP_OFFSET) {
+		int val;
+
+		scoped_guard(mutex, &mcu->lock) {
+			val = omnia_cmd_read_bit(mcu->client,
+						 OMNIA_CMD_GET_EXT_CONTROL_STATUS,
+						 OMNIA_EXT_CTL_PHY_SFP_AUTO);
+			if (val < 0)
+				return val;
+		}
+
+		if (val)
+			return GPIO_LINE_DIRECTION_IN;
+
+		return GPIO_LINE_DIRECTION_OUT;
+	}
+
+	if (omnia_gpios[offset].ctl_cmd)
+		return GPIO_LINE_DIRECTION_OUT;
+
+	return GPIO_LINE_DIRECTION_IN;
+}
+
+static int omnia_gpio_direction_input(struct gpio_chip *gc, unsigned int offset)
+{
+	const struct omnia_gpio *gpio = &omnia_gpios[offset];
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+
+	if (offset == OMNIA_GPIO_PHY_SFP_OFFSET)
+		return omnia_ctl_cmd(mcu, OMNIA_CMD_EXT_CONTROL,
+				     OMNIA_EXT_CTL_PHY_SFP_AUTO,
+				     OMNIA_EXT_CTL_PHY_SFP_AUTO);
+
+	if (gpio->ctl_cmd)
+		return -ENOTSUPP;
+
+	return 0;
+}
+
+static int omnia_gpio_direction_output(struct gpio_chip *gc,
+				       unsigned int offset, int value)
+{
+	const struct omnia_gpio *gpio = &omnia_gpios[offset];
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	u16 val, mask;
+
+	if (!gpio->ctl_cmd)
+		return -ENOTSUPP;
+
+	mask = BIT(gpio->ctl_bit);
+	val = value ? mask : 0;
+
+	if (offset == OMNIA_GPIO_PHY_SFP_OFFSET)
+		mask |= OMNIA_EXT_CTL_PHY_SFP_AUTO;
+
+	return omnia_ctl_cmd(mcu, gpio->ctl_cmd, val, mask);
+}
+
+static int omnia_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+	const struct omnia_gpio *gpio = &omnia_gpios[offset];
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+
+	/*
+	 * If firmware does not support the new interrupt API, we are informed
+	 * of every change of the status word by an interrupt from MCU and save
+	 * its value in the interrupt service routine. Simply return the saved
+	 * value.
+	 */
+	if (gpio->cmd == OMNIA_CMD_GET_STATUS_WORD &&
+	    !(mcu->features & OMNIA_FEAT_NEW_INT_API))
+		return test_bit(gpio->bit, &mcu->last_status);
+
+	guard(mutex)(&mcu->lock);
+
+	/*
+	 * If firmware does support the new interrupt API, we may have cached
+	 * the value of a GPIO in the interrupt service routine. If not, read
+	 * the relevant bit now.
+	 */
+	if (is_int_bit_valid(gpio) && test_bit(gpio->int_bit, &mcu->is_cached))
+		return test_bit(gpio->int_bit, &mcu->cached);
+
+	return omnia_cmd_read_bit(mcu->client, gpio->cmd, BIT(gpio->bit));
+}
+
+static unsigned long *
+_relevant_field_for_sts_cmd(u8 cmd, unsigned long *sts, unsigned long *ext_sts,
+			    unsigned long *ext_ctl)
+{
+	switch (cmd) {
+	case OMNIA_CMD_GET_STATUS_WORD:
+		return sts;
+	case OMNIA_CMD_GET_EXT_STATUS_DWORD:
+		return ext_sts;
+	case OMNIA_CMD_GET_EXT_CONTROL_STATUS:
+		return ext_ctl;
+	default:
+		return NULL;
+	}
+}
+
+static int omnia_gpio_get_multiple(struct gpio_chip *gc, unsigned long *mask,
+				   unsigned long *bits)
+{
+	unsigned long sts = 0, ext_sts = 0, ext_ctl = 0, *field;
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	struct i2c_client *client = mcu->client;
+	unsigned int i;
+	int err;
+
+	/* determine which bits to read from the 3 possible commands */
+	for_each_set_bit(i, mask, ARRAY_SIZE(omnia_gpios)) {
+		field = _relevant_field_for_sts_cmd(omnia_gpios[i].cmd,
+						    &sts, &ext_sts, &ext_ctl);
+		if (!field)
+			continue;
+
+		__set_bit(omnia_gpios[i].bit, field);
+	}
+
+	guard(mutex)(&mcu->lock);
+
+	if (mcu->features & OMNIA_FEAT_NEW_INT_API) {
+		/* read relevant bits from status */
+		err = omnia_cmd_read_bits(client, OMNIA_CMD_GET_STATUS_WORD,
+					  sts, &sts);
+		if (err)
+			return err;
+	} else {
+		/*
+		 * Use status word value cached in the interrupt service routine
+		 * if firmware does not support the new interrupt API.
+		 */
+		sts = mcu->last_status;
+	}
+
+	/* read relevant bits from extended status */
+	err = omnia_cmd_read_bits(client, OMNIA_CMD_GET_EXT_STATUS_DWORD,
+				  ext_sts, &ext_sts);
+	if (err)
+		return err;
+
+	/* read relevant bits from extended control */
+	err = omnia_cmd_read_bits(client, OMNIA_CMD_GET_EXT_CONTROL_STATUS,
+				  ext_ctl, &ext_ctl);
+	if (err)
+		return err;
+
+	/* assign relevant bits in result */
+	for_each_set_bit(i, mask, ARRAY_SIZE(omnia_gpios)) {
+		field = _relevant_field_for_sts_cmd(omnia_gpios[i].cmd,
+						    &sts, &ext_sts, &ext_ctl);
+		if (!field)
+			continue;
+
+		__assign_bit(i, bits, test_bit(omnia_gpios[i].bit, field));
+	}
+
+	return 0;
+}
+
+static void omnia_gpio_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	const struct omnia_gpio *gpio = &omnia_gpios[offset];
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	u16 val, mask;
+
+	if (!gpio->ctl_cmd)
+		return;
+
+	mask = BIT(gpio->ctl_bit);
+	val = value ? mask : 0;
+
+	omnia_ctl_cmd(mcu, gpio->ctl_cmd, val, mask);
+}
+
+static void omnia_gpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
+				    unsigned long *bits)
+{
+	unsigned long ctl = 0, ctl_mask = 0, ext_ctl = 0, ext_ctl_mask = 0;
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	unsigned int i;
+
+	for_each_set_bit(i, mask, ARRAY_SIZE(omnia_gpios)) {
+		unsigned long *field, *field_mask;
+		u8 bit = omnia_gpios[i].ctl_bit;
+
+		switch (omnia_gpios[i].ctl_cmd) {
+		case OMNIA_CMD_GENERAL_CONTROL:
+			field = &ctl;
+			field_mask = &ctl_mask;
+			break;
+		case OMNIA_CMD_EXT_CONTROL:
+			field = &ext_ctl;
+			field_mask = &ext_ctl_mask;
+			break;
+		default:
+			field = field_mask = NULL;
+			break;
+		}
+
+		if (!field)
+			continue;
+
+		__set_bit(bit, field_mask);
+		__assign_bit(bit, field, test_bit(i, bits));
+	}
+
+	guard(mutex)(&mcu->lock);
+
+	if (ctl_mask)
+		omnia_ctl_cmd_locked(mcu, OMNIA_CMD_GENERAL_CONTROL,
+				     ctl, ctl_mask);
+
+	if (ext_ctl_mask)
+		omnia_ctl_cmd_locked(mcu, OMNIA_CMD_EXT_CONTROL,
+				     ext_ctl, ext_ctl_mask);
+}
+
+static bool omnia_gpio_available(struct omnia_mcu *mcu,
+				 const struct omnia_gpio *gpio)
+{
+	if (gpio->feat_mask)
+		return (mcu->features & gpio->feat_mask) == gpio->feat;
+
+	if (gpio->feat)
+		return mcu->features & gpio->feat;
+
+	return true;
+}
+
+static int omnia_gpio_init_valid_mask(struct gpio_chip *gc,
+				      unsigned long *valid_mask,
+				      unsigned int ngpios)
+{
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+
+	for (unsigned int i = 0; i < ngpios; i++) {
+		const struct omnia_gpio *gpio = &omnia_gpios[i];
+
+		if (gpio->cmd || is_int_bit_valid(gpio))
+			__assign_bit(i, valid_mask,
+				     omnia_gpio_available(mcu, gpio));
+		else
+			__clear_bit(i, valid_mask);
+	}
+
+	return 0;
+}
+
+static int omnia_gpio_of_xlate(struct gpio_chip *gc,
+			       const struct of_phandle_args *gpiospec,
+			       u32 *flags)
+{
+	u32 bank, gpio;
+
+	if (WARN_ON(gpiospec->args_count != 3))
+		return -EINVAL;
+
+	if (flags)
+		*flags = gpiospec->args[2];
+
+	bank = gpiospec->args[0];
+	gpio = gpiospec->args[1];
+
+	switch (bank) {
+	case 0:
+		return gpio < 16 ? gpio : -EINVAL;
+	case 1:
+		return gpio < 32 ? 16 + gpio : -EINVAL;
+	case 2:
+		return gpio < 16 ? 48 + gpio : -EINVAL;
+	default:
+		return -EINVAL;
+	}
+}
+
+static void omnia_irq_shutdown(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	irq_hw_number_t hwirq = irqd_to_hwirq(d);
+	u8 bit = omnia_gpios[hwirq].int_bit;
+
+	__clear_bit(bit, &mcu->rising);
+	__clear_bit(bit, &mcu->falling);
+}
+
+static void omnia_irq_mask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	irq_hw_number_t hwirq = irqd_to_hwirq(d);
+	u8 bit = omnia_gpios[hwirq].int_bit;
+
+	if (!omnia_gpios[hwirq].cmd)
+		__clear_bit(bit, &mcu->rising);
+	__clear_bit(bit, &mcu->mask);
+	gpiochip_disable_irq(gc, hwirq);
+}
+
+static void omnia_irq_unmask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	irq_hw_number_t hwirq = irqd_to_hwirq(d);
+	u8 bit = omnia_gpios[hwirq].int_bit;
+
+	gpiochip_enable_irq(gc, hwirq);
+	__set_bit(bit, &mcu->mask);
+	if (!omnia_gpios[hwirq].cmd)
+		__set_bit(bit, &mcu->rising);
+}
+
+static int omnia_irq_set_type(struct irq_data *d, unsigned int type)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	irq_hw_number_t hwirq = irqd_to_hwirq(d);
+	struct device *dev = &mcu->client->dev;
+	u8 bit = omnia_gpios[hwirq].int_bit;
+
+	if (!(type & IRQ_TYPE_EDGE_BOTH)) {
+		dev_err(dev, "irq %u: unsupported type %u\n", d->irq, type);
+		return -EINVAL;
+	}
+
+	__assign_bit(bit, &mcu->rising, type & IRQ_TYPE_EDGE_RISING);
+	__assign_bit(bit, &mcu->falling, type & IRQ_TYPE_EDGE_FALLING);
+
+	return 0;
+}
+
+static void omnia_irq_bus_lock(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+
+	/* nothing to do if MCU firmware does not support new interrupt API */
+	if (!(mcu->features & OMNIA_FEAT_NEW_INT_API))
+		return;
+
+	mutex_lock(&mcu->lock);
+}
+
+/**
+ * omnia_mask_interleave - Interleaves the bytes from @rising and @falling
+ * @dst: the destination u8 array of interleaved bytes
+ * @rising: rising mask
+ * @falling: falling mask
+ *
+ * Interleaves the little-endian bytes from @rising and @falling words.
+ *
+ * If @rising = (r0, r1, r2, r3) and @falling = (f0, f1, f2, f3), the result is
+ * @dst = (r0, f0, r1, f1, r2, f2, r3, f3).
+ *
+ * The MCU receives an interrupt mask and reports a pending interrupt bitmap in
+ * this interleaved format. The rationale behind this is that the low-indexed
+ * bits are more important - in many cases, the user will be interested only in
+ * interrupts with indexes 0 to 7, and so the system can stop reading after
+ * first 2 bytes (r0, f0), to save time on the slow I2C bus.
+ *
+ * Feel free to remove this function and its inverse, omnia_mask_deinterleave,
+ * and use an appropriate bitmap_*() function once such a function exists.
+ */
+static void
+omnia_mask_interleave(u8 *dst, unsigned long rising, unsigned long falling)
+{
+	for (unsigned int i = 0; i < sizeof(u32); i++) {
+		dst[2 * i] = rising >> (8 * i);
+		dst[2 * i + 1] = falling >> (8 * i);
+	}
+}
+
+/**
+ * omnia_mask_deinterleave - Deinterleaves the bytes into @rising and @falling
+ * @src: the source u8 array containing the interleaved bytes
+ * @rising: pointer where to store the rising mask gathered from @src
+ * @falling: pointer where to store the falling mask gathered from @src
+ *
+ * This is the inverse function to omnia_mask_interleave.
+ */
+static void omnia_mask_deinterleave(const u8 *src, unsigned long *rising,
+				    unsigned long *falling)
+{
+	*rising = *falling = 0;
+
+	for (unsigned int i = 0; i < sizeof(u32); i++) {
+		*rising |= src[2 * i] << (8 * i);
+		*falling |= src[2 * i + 1] << (8 * i);
+	}
+}
+
+static void omnia_irq_bus_sync_unlock(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	struct device *dev = &mcu->client->dev;
+	u8 cmd[1 + OMNIA_CMD_INT_ARG_LEN];
+	unsigned long rising, falling;
+	int err;
+
+	/* nothing to do if MCU firmware does not support new interrupt API */
+	if (!(mcu->features & OMNIA_FEAT_NEW_INT_API))
+		return;
+
+	cmd[0] = OMNIA_CMD_SET_INT_MASK;
+
+	rising = mcu->rising & mcu->mask;
+	falling = mcu->falling & mcu->mask;
+
+	/* interleave the rising and falling bytes into the command arguments */
+	omnia_mask_interleave(&cmd[1], rising, falling);
+
+	dev_dbg(dev, "set int mask %8ph\n", &cmd[1]);
+
+	err = omnia_cmd_write(mcu->client, cmd, sizeof(cmd));
+	if (err) {
+		dev_err(dev, "Cannot set mask: %d\n", err);
+		goto unlock;
+	}
+
+	/*
+	 * Remember which GPIOs have both rising and falling interrupts enabled.
+	 * For those we will cache their value so that .get() method is faster.
+	 * We also need to forget cached values of GPIOs that aren't cached
+	 * anymore.
+	 */
+	mcu->both = rising & falling;
+	mcu->is_cached &= mcu->both;
+
+unlock:
+	mutex_unlock(&mcu->lock);
+}
+
+static const struct irq_chip omnia_mcu_irq_chip = {
+	.name			= "Turris Omnia MCU interrupts",
+	.irq_shutdown		= omnia_irq_shutdown,
+	.irq_mask		= omnia_irq_mask,
+	.irq_unmask		= omnia_irq_unmask,
+	.irq_set_type		= omnia_irq_set_type,
+	.irq_bus_lock		= omnia_irq_bus_lock,
+	.irq_bus_sync_unlock	= omnia_irq_bus_sync_unlock,
+	.flags			= IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
+};
+
+static void omnia_irq_init_valid_mask(struct gpio_chip *gc,
+				      unsigned long *valid_mask,
+				      unsigned int ngpios)
+{
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+
+	for (unsigned int i = 0; i < ngpios; i++) {
+		const struct omnia_gpio *gpio = &omnia_gpios[i];
+
+		if (is_int_bit_valid(gpio))
+			__assign_bit(i, valid_mask,
+				     omnia_gpio_available(mcu, gpio));
+		else
+			__clear_bit(i, valid_mask);
+	}
+}
+
+static int omnia_irq_init_hw(struct gpio_chip *gc)
+{
+	struct omnia_mcu *mcu = gpiochip_get_data(gc);
+	u8 cmd[1 + OMNIA_CMD_INT_ARG_LEN] = {};
+
+	cmd[0] = OMNIA_CMD_SET_INT_MASK;
+
+	return omnia_cmd_write(mcu->client, cmd, sizeof(cmd));
+}
+
+/*
+ * Determine how many bytes we need to read from the reply to the
+ * OMNIA_CMD_GET_INT_AND_CLEAR command in order to retrieve all unmasked
+ * interrupts.
+ */
+static unsigned int
+omnia_irq_compute_pending_length(unsigned long rising, unsigned long falling)
+{
+	return max(omnia_compute_reply_length(rising, true, 0),
+		   omnia_compute_reply_length(falling, true, 1));
+}
+
+static bool omnia_irq_read_pending_new(struct omnia_mcu *mcu,
+				       unsigned long *pending)
+{
+	struct device *dev = &mcu->client->dev;
+	u8 reply[OMNIA_CMD_INT_ARG_LEN] = {};
+	unsigned long rising, falling;
+	unsigned int len;
+	int err;
+
+	len = omnia_irq_compute_pending_length(mcu->rising & mcu->mask,
+					       mcu->falling & mcu->mask);
+	if (!len)
+		return false;
+
+	guard(mutex)(&mcu->lock);
+
+	err = omnia_cmd_read(mcu->client, OMNIA_CMD_GET_INT_AND_CLEAR, reply,
+			     len);
+	if (err) {
+		dev_err(dev, "Cannot read pending IRQs: %d\n", err);
+		return false;
+	}
+
+	/* deinterleave the reply bytes into rising and falling */
+	omnia_mask_deinterleave(reply, &rising, &falling);
+
+	rising &= mcu->mask;
+	falling &= mcu->mask;
+	*pending = rising | falling;
+
+	/* cache values for GPIOs that have both edges enabled */
+	mcu->is_cached &= ~(rising & falling);
+	mcu->is_cached |= mcu->both & (rising ^ falling);
+	mcu->cached = (mcu->cached | rising) & ~falling;
+
+	return true;
+}
+
+static int omnia_read_status_word_old_fw(struct omnia_mcu *mcu,
+					 unsigned long *status)
+{
+	u16 raw_status;
+	int err;
+
+	err = omnia_cmd_read_u16(mcu->client, OMNIA_CMD_GET_STATUS_WORD,
+				 &raw_status);
+	if (err)
+		return err;
+
+	/*
+	 * Old firmware has a bug wherein it never resets the USB port
+	 * overcurrent bits back to zero. Ignore them.
+	 */
+	*status = raw_status & ~(OMNIA_STS_USB30_OVC | OMNIA_STS_USB31_OVC);
+
+	return 0;
+}
+
+static void button_release_emul_fn(struct work_struct *work)
+{
+	struct omnia_mcu *mcu = container_of(to_delayed_work(work),
+					     struct omnia_mcu,
+					     button_release_emul_work);
+
+	mcu->button_pressed_emul = false;
+	generic_handle_irq_safe(mcu->client->irq);
+}
+
+static void
+fill_int_from_sts(unsigned long *rising, unsigned long *falling,
+		  unsigned long rising_sts, unsigned long falling_sts,
+		  unsigned long sts_bit, unsigned long int_bit)
+{
+	if (rising_sts & sts_bit)
+		*rising |= int_bit;
+	if (falling_sts & sts_bit)
+		*falling |= int_bit;
+}
+
+static bool omnia_irq_read_pending_old(struct omnia_mcu *mcu,
+				       unsigned long *pending)
+{
+	unsigned long status, rising_sts, falling_sts, rising, falling;
+	struct device *dev = &mcu->client->dev;
+	int err;
+
+	guard(mutex)(&mcu->lock);
+
+	err = omnia_read_status_word_old_fw(mcu, &status);
+	if (err) {
+		dev_err(dev, "Cannot read pending IRQs: %d\n", err);
+		return false;
+	}
+
+	/*
+	 * The old firmware triggers an interrupt whenever status word changes,
+	 * but does not inform about which bits rose or fell. We need to compute
+	 * this here by comparing with the last status word value.
+	 *
+	 * The OMNIA_STS_BUTTON_PRESSED bit needs special handling, because the
+	 * old firmware clears the OMNIA_STS_BUTTON_PRESSED bit on successful
+	 * completion of the OMNIA_CMD_GET_STATUS_WORD command, resulting in
+	 * another interrupt:
+	 * - first we get an interrupt, we read the status word where
+	 *   OMNIA_STS_BUTTON_PRESSED is present,
+	 * - MCU clears the OMNIA_STS_BUTTON_PRESSED bit because we read the
+	 *   status word,
+	 * - we get another interrupt because the status word changed again
+	 *   (the OMNIA_STS_BUTTON_PRESSED bit was cleared).
+	 *
+	 * The gpiolib-cdev, gpiolib-sysfs and gpio-keys input driver all call
+	 * the gpiochip's .get() method after an edge event on a requested GPIO
+	 * occurs.
+	 *
+	 * We ensure that the .get() method reads 1 for the button GPIO for some
+	 * time.
+	 */
+
+	if (status & OMNIA_STS_BUTTON_PRESSED) {
+		mcu->button_pressed_emul = true;
+		mod_delayed_work(system_wq, &mcu->button_release_emul_work,
+				 msecs_to_jiffies(FRONT_BUTTON_RELEASE_DELAY_MS));
+	} else if (mcu->button_pressed_emul) {
+		status |= OMNIA_STS_BUTTON_PRESSED;
+	}
+
+	rising_sts = ~mcu->last_status & status;
+	falling_sts = mcu->last_status & ~status;
+
+	mcu->last_status = status;
+
+	/*
+	 * Fill in the relevant interrupt bits from status bits for CARD_DET,
+	 * MSATA_IND and BUTTON_PRESSED.
+	 */
+	rising = 0;
+	falling = 0;
+	fill_int_from_sts(&rising, &falling, rising_sts, falling_sts,
+			  OMNIA_STS_CARD_DET, OMNIA_INT_CARD_DET);
+	fill_int_from_sts(&rising, &falling, rising_sts, falling_sts,
+			  OMNIA_STS_MSATA_IND, OMNIA_INT_MSATA_IND);
+	fill_int_from_sts(&rising, &falling, rising_sts, falling_sts,
+			  OMNIA_STS_BUTTON_PRESSED, OMNIA_INT_BUTTON_PRESSED);
+
+	/* Use only bits that are enabled */
+	rising &= mcu->rising & mcu->mask;
+	falling &= mcu->falling & mcu->mask;
+	*pending = rising | falling;
+
+	return true;
+}
+
+static bool omnia_irq_read_pending(struct omnia_mcu *mcu,
+				   unsigned long *pending)
+{
+	if (mcu->features & OMNIA_FEAT_NEW_INT_API)
+		return omnia_irq_read_pending_new(mcu, pending);
+	else
+		return omnia_irq_read_pending_old(mcu, pending);
+}
+
+static irqreturn_t omnia_irq_thread_handler(int irq, void *dev_id)
+{
+	struct omnia_mcu *mcu = dev_id;
+	struct irq_domain *domain;
+	unsigned long pending;
+	unsigned int i;
+
+	if (!omnia_irq_read_pending(mcu, &pending))
+		return IRQ_NONE;
+
+	domain = mcu->gc.irq.domain;
+
+	for_each_set_bit(i, &pending, 32) {
+		unsigned int nested_irq;
+
+		nested_irq = irq_find_mapping(domain, omnia_int_to_gpio_idx[i]);
+
+		handle_nested_irq(nested_irq);
+	}
+
+	return IRQ_RETVAL(pending);
+}
+
+static const char * const front_button_modes[] = { "mcu", "cpu" };
+
+static ssize_t front_button_mode_show(struct device *dev,
+				      struct device_attribute *a, char *buf)
+{
+	struct omnia_mcu *mcu = dev_get_drvdata(dev);
+	int val;
+
+	if (mcu->features & OMNIA_FEAT_NEW_INT_API) {
+		val = omnia_cmd_read_bit(mcu->client, OMNIA_CMD_GET_STATUS_WORD,
+					 OMNIA_STS_BUTTON_MODE);
+		if (val < 0)
+			return val;
+	} else {
+		val = !!(mcu->last_status & OMNIA_STS_BUTTON_MODE);
+	}
+
+	return sysfs_emit(buf, "%s\n", front_button_modes[val]);
+}
+
+static ssize_t front_button_mode_store(struct device *dev,
+				       struct device_attribute *a,
+				       const char *buf, size_t count)
+{
+	struct omnia_mcu *mcu = dev_get_drvdata(dev);
+	int err, i;
+
+	i = sysfs_match_string(front_button_modes, buf);
+	if (i < 0)
+		return i;
+
+	err = omnia_ctl_cmd_locked(mcu, OMNIA_CMD_GENERAL_CONTROL,
+				   i ? OMNIA_CTL_BUTTON_MODE : 0,
+				   OMNIA_CTL_BUTTON_MODE);
+	if (err)
+		return err;
+
+	return count;
+}
+static DEVICE_ATTR_RW(front_button_mode);
+
+static struct attribute *omnia_mcu_gpio_attrs[] = {
+	&dev_attr_front_button_mode.attr,
+	NULL
+};
+
+const struct attribute_group omnia_mcu_gpio_group = {
+	.attrs = omnia_mcu_gpio_attrs,
+};
+
+int omnia_mcu_register_gpiochip(struct omnia_mcu *mcu)
+{
+	bool new_api = mcu->features & OMNIA_FEAT_NEW_INT_API;
+	struct device *dev = &mcu->client->dev;
+	unsigned long irqflags;
+	int err;
+
+	err = devm_mutex_init(dev, &mcu->lock);
+	if (err)
+		return err;
+
+	mcu->gc.request = omnia_gpio_request;
+	mcu->gc.get_direction = omnia_gpio_get_direction;
+	mcu->gc.direction_input = omnia_gpio_direction_input;
+	mcu->gc.direction_output = omnia_gpio_direction_output;
+	mcu->gc.get = omnia_gpio_get;
+	mcu->gc.get_multiple = omnia_gpio_get_multiple;
+	mcu->gc.set = omnia_gpio_set;
+	mcu->gc.set_multiple = omnia_gpio_set_multiple;
+	mcu->gc.init_valid_mask = omnia_gpio_init_valid_mask;
+	mcu->gc.can_sleep = true;
+	mcu->gc.names = omnia_mcu_gpio_templates;
+	mcu->gc.base = -1;
+	mcu->gc.ngpio = ARRAY_SIZE(omnia_gpios);
+	mcu->gc.label = "Turris Omnia MCU GPIOs";
+	mcu->gc.parent = dev;
+	mcu->gc.owner = THIS_MODULE;
+	mcu->gc.of_gpio_n_cells = 3;
+	mcu->gc.of_xlate = omnia_gpio_of_xlate;
+
+	gpio_irq_chip_set_chip(&mcu->gc.irq, &omnia_mcu_irq_chip);
+	/* This will let us handle the parent IRQ in the driver */
+	mcu->gc.irq.parent_handler = NULL;
+	mcu->gc.irq.num_parents = 0;
+	mcu->gc.irq.parents = NULL;
+	mcu->gc.irq.default_type = IRQ_TYPE_NONE;
+	mcu->gc.irq.handler = handle_bad_irq;
+	mcu->gc.irq.threaded = true;
+	if (new_api)
+		mcu->gc.irq.init_hw = omnia_irq_init_hw;
+	mcu->gc.irq.init_valid_mask = omnia_irq_init_valid_mask;
+
+	err = devm_gpiochip_add_data(dev, &mcu->gc, mcu);
+	if (err)
+		return dev_err_probe(dev, err, "Cannot add GPIO chip\n");
+
+	/*
+	 * Before requesting the interrupt, if firmware does not support the new
+	 * interrupt API, we need to cache the value of the status word, so that
+	 * when it changes, we may compare the new value with the cached one in
+	 * the interrupt handler.
+	 */
+	if (!new_api) {
+		err = omnia_read_status_word_old_fw(mcu, &mcu->last_status);
+		if (err)
+			return dev_err_probe(dev, err,
+					     "Cannot read status word\n");
+
+		INIT_DELAYED_WORK(&mcu->button_release_emul_work,
+				  button_release_emul_fn);
+	}
+
+	irqflags = IRQF_ONESHOT;
+	if (new_api)
+		irqflags |= IRQF_TRIGGER_LOW;
+	else
+		irqflags |= IRQF_TRIGGER_FALLING;
+
+	err = devm_request_threaded_irq(dev, mcu->client->irq, NULL,
+					omnia_irq_thread_handler, irqflags,
+					"turris-omnia-mcu", mcu);
+	if (err)
+		return dev_err_probe(dev, err, "Cannot request IRQ\n");
+
+	if (!new_api) {
+		/*
+		 * The button_release_emul_work has to be initialized before the
+		 * thread is requested, and on driver remove it needs to be
+		 * canceled before the thread is freed. Therefore we can't use
+		 * devm_delayed_work_autocancel() directly, because the order
+		 *   devm_delayed_work_autocancel();
+		 *   devm_request_threaded_irq();
+		 * would cause improper release order:
+		 *   free_irq();
+		 *   cancel_delayed_work_sync();
+		 * Instead we first initialize the work above, and only now
+		 * after IRQ is requested we add the work devm action.
+		 */
+		err = devm_add_action(dev, devm_delayed_work_drop,
+				      &mcu->button_release_emul_work);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}

drivers/platform/cznic/turris-omnia-mcu.h

@@ -8,8 +8,12 @@
 #ifndef __TURRIS_OMNIA_MCU_H
 #define __TURRIS_OMNIA_MCU_H
 
+#include <linux/bitops.h>
+#include <linux/gpio/driver.h>
 #include <linux/if_ether.h>
+#include <linux/mutex.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 #include <asm/byteorder.h>
 
 struct i2c_client;
@@ -23,18 +27,78 @@ struct omnia_mcu {
 	u64 board_serial_number;
 	u8 board_first_mac[ETH_ALEN];
 	u8 board_revision;
+
+	/* GPIO chip */
+	struct gpio_chip gc;
+	struct mutex lock;
+	unsigned long mask, rising, falling, both, cached, is_cached;
+	/* Old MCU firmware handling needs the following */
+	struct delayed_work button_release_emul_work;
+	unsigned long last_status;
+	bool button_pressed_emul;
 };
 
 int omnia_cmd_write_read(const struct i2c_client *client,
 			 void *cmd, unsigned int cmd_len,
 			 void *reply, unsigned int reply_len);
 
+static inline int omnia_cmd_write(const struct i2c_client *client, void *cmd,
+				  unsigned int len)
+{
+	return omnia_cmd_write_read(client, cmd, len, NULL, 0);
+}
+
 static inline int omnia_cmd_read(const struct i2c_client *client, u8 cmd,
 				 void *reply, unsigned int len)
 {
 	return omnia_cmd_write_read(client, &cmd, 1, reply, len);
 }
 
+static inline unsigned int
+omnia_compute_reply_length(unsigned long mask, bool interleaved,
+			   unsigned int offset)
+{
+	if (!mask)
+		return 0;
+
+	return ((__fls(mask) >> 3) << interleaved) + 1 + offset;
+}
+
+/* Returns 0 on success */
+static inline int omnia_cmd_read_bits(const struct i2c_client *client, u8 cmd,
+				      unsigned long bits, unsigned long *dst)
+{
+	__le32 reply;
+	int err;
+
+	if (!bits) {
+		*dst = 0;
+		return 0;
+	}
+
+	err = omnia_cmd_read(client, cmd, &reply,
+			     omnia_compute_reply_length(bits, false, 0));
+	if (err)
+		return err;
+
+	*dst = le32_to_cpu(reply) & bits;
+
+	return 0;
+}
+
+static inline int omnia_cmd_read_bit(const struct i2c_client *client, u8 cmd,
+				     unsigned long bit)
+{
+	unsigned long reply;
+	int err;
+
+	err = omnia_cmd_read_bits(client, cmd, bit, &reply);
+	if (err)
+		return err;
+
+	return !!reply;
+}
+
 static inline int omnia_cmd_read_u32(const struct i2c_client *client, u8 cmd,
 				     u32 *dst)
 {
@@ -71,4 +135,8 @@ static inline int omnia_cmd_read_u8(const struct i2c_client *client, u8 cmd,
 	return omnia_cmd_read(client, cmd, reply, sizeof(*reply));
 }
 
+extern const struct attribute_group omnia_mcu_gpio_group;
+
+int omnia_mcu_register_gpiochip(struct omnia_mcu *mcu);
+
 #endif /* __TURRIS_OMNIA_MCU_H */