diff mbox series

[v5,2/3] gpio: ch341: add GPIO MFD cell driver for the CH341

Message ID 20220401023306.79532-3-frank@zago.net
State New
Headers show
Series [v5,1/3] mfd: ch341: add core driver for the WCH CH341 in I2C/SPI/GPIO mode | expand

Commit Message

Frank Zago April 1, 2022, 2:33 a.m. UTC 
The GPIO interface offers 16 GPIOs. 6 are read/write, and 10 are
read-only.

Signed-off-by: frank zago <frank@zago.net>
---
 MAINTAINERS               |   1 +
 drivers/gpio/Kconfig      |  10 +
 drivers/gpio/Makefile     |   1 +
 drivers/gpio/gpio-ch341.c | 383 ++++++++++++++++++++++++++++++++++++++
 drivers/mfd/ch341-core.c  |   3 +
 5 files changed, 398 insertions(+)
 create mode 100644 drivers/gpio/gpio-ch341.c

Comments

Johan Hovold May 23, 2022, 4:16 p.m. UTC | #1 
On Thu, Mar 31, 2022 at 09:33:05PM -0500, frank zago wrote:
> The GPIO interface offers 16 GPIOs. 6 are read/write, and 10 are
> read-only.
> 
> Signed-off-by: frank zago <frank@zago.net>
> ---

> +struct ch341_gpio {
> +	struct gpio_chip gpio;
> +	struct mutex gpio_lock;
> +	u16 gpio_dir;		/* 1 bit per pin, 0=IN, 1=OUT. */
> +	u16 gpio_last_read;	/* last GPIO values read */
> +	u16 gpio_last_written;	/* last GPIO values written */
> +	union {
> +		u8 gpio_buf[SEG_SIZE];
> +		__le16 gpio_buf_status;
> +	};
> +
> +	struct urb *irq_urb;
> +	struct usb_anchor irq_urb_out;
> +	u8 irq_buf[CH341_USB_MAX_INTR_SIZE];
> +	struct irq_chip irq_chip;
> +
> +	struct ch341_device *ch341;
> +};

> +static void ch341_complete_intr_urb(struct urb *urb)
> +{
> +	struct ch341_gpio *dev = urb->context;
> +	int rc;
> +
> +	if (urb->status) {
> +		usb_unanchor_urb(dev->irq_urb);

URBs are unanchored by USB core on completion.

> +	} else {
> +		/*
> +		 * Data is 8 bytes. Byte 0 might be the length of
> +		 * significant data, which is 3 more bytes. Bytes 1
> +		 * and 2, and possibly 3, are the pin status. The byte
> +		 * order is different than for the GET_STATUS
> +		 * command. Byte 1 is GPIOs 8 to 15, and byte 2 is
> +		 * GPIOs 0 to 7.
> +		 */
> +
> +		handle_nested_irq(irq_find_mapping(dev->gpio.irq.domain,
> +						   CH341_GPIO_INT_LINE));
> +
> +		rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
> +		if (rc)
> +			usb_unanchor_urb(dev->irq_urb);
> +	}
> +}

> +static void ch341_gpio_irq_enable(struct irq_data *data)
> +{
> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
> +	int rc;
> +
> +	/*
> +	 * The URB might have just been unlinked in
> +	 * ch341_gpio_irq_disable, but the completion handler hasn't
> +	 * been called yet.
> +	 */
> +	if (!usb_wait_anchor_empty_timeout(&dev->irq_urb_out, 5000))
> +		usb_kill_anchored_urbs(&dev->irq_urb_out);
> +
> +	usb_anchor_urb(dev->irq_urb, &dev->irq_urb_out);
> +	rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
> +	if (rc)
> +		usb_unanchor_urb(dev->irq_urb);

This looks confused and broken.

usb_kill_anchored_urbs() can sleep so either calling it is broken or
using GFP_ATOMIC is unnecessary.

And isn't this function called multiple times when enabling more than
one irq?!

> +}
> +
> +static void ch341_gpio_irq_disable(struct irq_data *data)
> +{
> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
> +
> +	usb_unlink_urb(dev->irq_urb);

Same here...

> +}
> +
> +static int ch341_gpio_remove(struct platform_device *pdev)
> +{
> +	struct ch341_gpio *dev = platform_get_drvdata(pdev);
> +
> +	usb_kill_anchored_urbs(&dev->irq_urb_out);

You only have one URB...

And what prevents it from being resubmitted here?

> +	gpiochip_remove(&dev->gpio);
> +	usb_free_urb(dev->irq_urb);
> +
> +	return 0;
> +}
> +
> +static int ch341_gpio_probe(struct platform_device *pdev)
> +{
> +	struct ch341_device *ch341 = dev_get_drvdata(pdev->dev.parent);
> +	struct gpio_irq_chip *girq;
> +	struct ch341_gpio *dev;
> +	struct gpio_chip *gpio;
> +	int rc;
> +
> +	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
> +	if (dev == NULL)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, dev);
> +	dev->ch341 = ch341;
> +	mutex_init(&dev->gpio_lock);
> +
> +	gpio = &dev->gpio;
> +	gpio->label = dev_name(&pdev->dev);
> +	gpio->parent = &pdev->dev;
> +	gpio->owner = THIS_MODULE;
> +	gpio->get_direction = ch341_gpio_get_direction;
> +	gpio->direction_input = ch341_gpio_direction_input;
> +	gpio->direction_output = ch341_gpio_direction_output;
> +	gpio->get = ch341_gpio_get;
> +	gpio->get_multiple = ch341_gpio_get_multiple;
> +	gpio->set = ch341_gpio_set;
> +	gpio->set_multiple = ch341_gpio_set_multiple;
> +	gpio->base = -1;
> +	gpio->ngpio = CH341_GPIO_NUM_PINS;
> +	gpio->can_sleep = true;
> +
> +	dev->irq_chip.name = dev_name(&pdev->dev);
> +	dev->irq_chip.irq_set_type = ch341_gpio_irq_set_type;
> +	dev->irq_chip.irq_enable = ch341_gpio_irq_enable;
> +	dev->irq_chip.irq_disable = ch341_gpio_irq_disable;
> +
> +	girq = &gpio->irq;
> +	girq->chip = &dev->irq_chip;
> +	girq->handler = handle_simple_irq;
> +	girq->default_type = IRQ_TYPE_NONE;
> +
> +	/* Create an URB for handling interrupt */
> +	dev->irq_urb = usb_alloc_urb(0, GFP_KERNEL);
> +	if (!dev->irq_urb)
> +		return dev_err_probe(&pdev->dev, -ENOMEM, "Cannot allocate the int URB\n");
> +
> +	usb_fill_int_urb(dev->irq_urb, ch341->usb_dev,
> +			 usb_rcvintpipe(ch341->usb_dev, ch341->ep_intr),
> +			 dev->irq_buf, CH341_USB_MAX_INTR_SIZE,
> +			 ch341_complete_intr_urb, dev, ch341->ep_intr_interval);
> +
> +	init_usb_anchor(&dev->irq_urb_out);
> +
> +	rc = gpiochip_add_data(gpio, dev);
> +	if (rc) {
> +		rc = dev_err_probe(&pdev->dev, rc, "Could not add GPIO\n");
> +		goto release_urb;
> +	}
> +
> +	return 0;
> +
> +release_urb:
> +	usb_free_urb(dev->irq_urb);
> +
> +	return rc;
> +}

Johan
Frank Zago June 16, 2022, 1:29 a.m. UTC | #2 
On 5/23/22 11:16, Johan Hovold wrote:

>> +static void ch341_complete_intr_urb(struct urb *urb)
>> +{
>> +	struct ch341_gpio *dev = urb->context;
>> +	int rc;
>> +
>> +	if (urb->status) {
>> +		usb_unanchor_urb(dev->irq_urb);
> 
> URBs are unanchored by USB core on completion.

Fixed.

> 
>> +static void ch341_gpio_irq_enable(struct irq_data *data)
>> +{
>> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
>> +	int rc;
>> +
>> +	/*
>> +	 * The URB might have just been unlinked in
>> +	 * ch341_gpio_irq_disable, but the completion handler hasn't
>> +	 * been called yet.
>> +	 */
>> +	if (!usb_wait_anchor_empty_timeout(&dev->irq_urb_out, 5000))
>> +		usb_kill_anchored_urbs(&dev->irq_urb_out);
>> +
>> +	usb_anchor_urb(dev->irq_urb, &dev->irq_urb_out);
>> +	rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
>> +	if (rc)
>> +		usb_unanchor_urb(dev->irq_urb);
> 
> This looks confused and broken.
> 
> usb_kill_anchored_urbs() can sleep so either calling it is broken or
> using GFP_ATOMIC is unnecessary.

Right, that function can sleep. I changed GFP_ATOMIC to GFP_KERNEL.

> 
> And isn't this function called multiple times when enabling more than
> one irq?!

There's only one IRQ, so only one URB will be posted at a time. It
is reposted as soon as it comes back unless the IRQ is disabled or
the device stops.


> 
>> +}
>> +
>> +static void ch341_gpio_irq_disable(struct irq_data *data)
>> +{
>> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
>> +
>> +	usb_unlink_urb(dev->irq_urb);
> 
> Same here...
> 
>> +}
>> +
>> +static int ch341_gpio_remove(struct platform_device *pdev)
>> +{
>> +	struct ch341_gpio *dev = platform_get_drvdata(pdev);
>> +
>> +	usb_kill_anchored_urbs(&dev->irq_urb_out);
> 
> You only have one URB...
> 
> And what prevents it from being resubmitted here?

I don't see what would resubmit it here. The gpio is being released.

Frank.
Johan Hovold June 20, 2022, 10:04 a.m. UTC | #3 
On Wed, Jun 15, 2022 at 08:29:31PM -0500, Frank Zago wrote:
> On 5/23/22 11:16, Johan Hovold wrote:

> >> +static void ch341_gpio_irq_enable(struct irq_data *data)
> >> +{
> >> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
> >> +	int rc;
> >> +
> >> +	/*
> >> +	 * The URB might have just been unlinked in
> >> +	 * ch341_gpio_irq_disable, but the completion handler hasn't
> >> +	 * been called yet.
> >> +	 */
> >> +	if (!usb_wait_anchor_empty_timeout(&dev->irq_urb_out, 5000))
> >> +		usb_kill_anchored_urbs(&dev->irq_urb_out);
> >> +
> >> +	usb_anchor_urb(dev->irq_urb, &dev->irq_urb_out);
> >> +	rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
> >> +	if (rc)
> >> +		usb_unanchor_urb(dev->irq_urb);
> > 
> > This looks confused and broken.
> > 
> > usb_kill_anchored_urbs() can sleep so either calling it is broken or
> > using GFP_ATOMIC is unnecessary.
> 
> Right, that function can sleep. I changed GFP_ATOMIC to GFP_KERNEL.

These callbacks can be called in atomic context so that's not an option,
I'm afraid.

> > And isn't this function called multiple times when enabling more than
> > one irq?!
> 
> There's only one IRQ, so only one URB will be posted at a time. It
> is reposted as soon as it comes back unless the IRQ is disabled or
> the device stops.

AFAICT you have up to 16 (CH341_GPIO_NUM_PINS) interrupts, not one. So I
still say this is broken.

> >> +}
> >> +
> >> +static void ch341_gpio_irq_disable(struct irq_data *data)
> >> +{
> >> +	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
> >> +
> >> +	usb_unlink_urb(dev->irq_urb);
> > 
> > Same here...

> >> +}
> >> +
> >> +static int ch341_gpio_remove(struct platform_device *pdev)
> >> +{
> >> +	struct ch341_gpio *dev = platform_get_drvdata(pdev);
> >> +
> >> +	usb_kill_anchored_urbs(&dev->irq_urb_out);
> > 
> > You only have one URB...
> > 
> > And what prevents it from being resubmitted here?
> 
> I don't see what would resubmit it here. The gpio is being released.

Your implementation needs to handle racing requests. The gpio chip is
still registered here.

Johan
diff mbox series

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index b61af813fb9f..757ab4f6f9f6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21215,6 +21215,7 @@  WINCHIPHEAD CH341 I2C/GPIO MFD DRIVER
 M:	Frank Zago <frank@zago.net>
 L:	linux-usb@vger.kernel.org
 S:	Maintained
+F:	drivers/gpio/gpio-ch341.c
 F:	drivers/mfd/ch341-core.c
 F:	include/linux/mfd/ch341.h
 
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 45764ec3b2eb..0e868c26daf6 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1652,6 +1652,16 @@  endmenu
 menu "USB GPIO expanders"
 	depends on USB
 
+config GPIO_CH341
+	tristate "CH341 USB to GPIO support"
+	select MFD_CH341
+	help
+	  If you say yes to this option, GPIO support will be included for the
+	  WCH CH341, a USB to I2C/SPI/GPIO interface.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called gpio-ch341.
+
 config GPIO_VIPERBOARD
 	tristate "Viperboard GPIO a & b support"
 	depends on MFD_VIPERBOARD
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 14352f6dfe8e..beef802cbfb1 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -44,6 +44,7 @@  obj-$(CONFIG_GPIO_BD9571MWV)		+= gpio-bd9571mwv.o
 obj-$(CONFIG_GPIO_BRCMSTB)		+= gpio-brcmstb.o
 obj-$(CONFIG_GPIO_BT8XX)		+= gpio-bt8xx.o
 obj-$(CONFIG_GPIO_CADENCE)		+= gpio-cadence.o
+obj-$(CONFIG_GPIO_CH341)		+= gpio-ch341.o
 obj-$(CONFIG_GPIO_CLPS711X)		+= gpio-clps711x.o
 obj-$(CONFIG_GPIO_SNPS_CREG)		+= gpio-creg-snps.o
 obj-$(CONFIG_GPIO_CRYSTAL_COVE)		+= gpio-crystalcove.o
diff --git a/drivers/gpio/gpio-ch341.c b/drivers/gpio/gpio-ch341.c
new file mode 100644
index 000000000000..8e81ccf93d71
--- /dev/null
+++ b/drivers/gpio/gpio-ch341.c
@@ -0,0 +1,383 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GPIO cell driver for the CH341A and CH341B chips.
+ *
+ * Copyright 2022, Frank Zago
+ * Copyright (c) 2017 Gunar Schorcht (gunar@schorcht.net)
+ * Copyright (c) 2016 Tse Lun Bien
+ * Copyright (c) 2014 Marco Gittler
+ * Copyright (c) 2006-2007 Till Harbaum (Till@Harbaum.org)
+ */
+
+/*
+ * Notes.
+ *
+ * For the CH341, 0=IN, 1=OUT, but for the GPIO subsystem, 1=IN and
+ * 0=OUT. Translation happens in a couple places.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/usb.h>
+
+#include <linux/gpio/driver.h>
+
+#include <linux/mfd/ch341.h>
+
+#define CH341_GPIO_NUM_PINS         16    /* Number of GPIO pins */
+
+/* GPIO chip commands */
+#define CH341_PARA_CMD_STS          0xA0  /* Get pins status */
+#define CH341_CMD_UIO_STREAM        0xAB  /* pin IO stream command */
+
+#define CH341_CMD_UIO_STM_OUT       0x80  /* pin IO interface OUT command (D0~D5) */
+#define CH341_CMD_UIO_STM_DIR       0x40  /* pin IO interface DIR command (D0~D5) */
+#define CH341_CMD_UIO_STM_END       0x20  /* pin IO interface END command */
+
+#define CH341_USB_MAX_INTR_SIZE 8
+
+struct ch341_gpio {
+	struct gpio_chip gpio;
+	struct mutex gpio_lock;
+	u16 gpio_dir;		/* 1 bit per pin, 0=IN, 1=OUT. */
+	u16 gpio_last_read;	/* last GPIO values read */
+	u16 gpio_last_written;	/* last GPIO values written */
+	union {
+		u8 gpio_buf[SEG_SIZE];
+		__le16 gpio_buf_status;
+	};
+
+	struct urb *irq_urb;
+	struct usb_anchor irq_urb_out;
+	u8 irq_buf[CH341_USB_MAX_INTR_SIZE];
+	struct irq_chip irq_chip;
+
+	struct ch341_device *ch341;
+};
+
+/*
+ * Masks to describe the 16 GPIOs. Pins D0 to D5 (mapped to GPIOs 0 to
+ * 5) can do input/output, but the other pins are input-only.
+ */
+static const u16 pin_can_output = 0b111111;
+
+/* Only GPIO 10 (INT# line) has hardware interrupt */
+#define CH341_GPIO_INT_LINE 10
+
+/* Send a command and get a reply if requested */
+static int gpio_transfer(struct ch341_gpio *dev, int out_len, int in_len)
+{
+	struct ch341_device *ch341 = dev->ch341;
+	int actual;
+	int rc;
+
+	mutex_lock(&ch341->usb_lock);
+
+	rc = usb_bulk_msg(ch341->usb_dev,
+			  usb_sndbulkpipe(ch341->usb_dev, ch341->ep_out),
+			  dev->gpio_buf, out_len,
+			  &actual, DEFAULT_TIMEOUT_MS);
+	if (rc < 0)
+		goto out_unlock;
+
+	if (in_len == 0)
+		goto out_unlock;
+
+	rc = usb_bulk_msg(ch341->usb_dev,
+			  usb_rcvbulkpipe(ch341->usb_dev, ch341->ep_in),
+			  dev->gpio_buf, SEG_SIZE, &actual, DEFAULT_TIMEOUT_MS);
+
+out_unlock:
+	mutex_unlock(&ch341->usb_lock);
+
+	if (rc < 0)
+		return rc;
+
+	return actual;
+}
+
+/* Read the GPIO line status. */
+static int read_inputs(struct ch341_gpio *dev)
+{
+	int rc;
+
+	mutex_lock(&dev->gpio_lock);
+
+	dev->gpio_buf[0] = CH341_PARA_CMD_STS;
+
+	rc = gpio_transfer(dev, 1, 1);
+
+	/*
+	 * The status command returns 6 bytes of data. Byte 0 has
+	 * status for lines 0 to 7, and byte 1 is lines 8 to 15. The
+	 * 3rd has the status for the SCL/SDA/SCK pins. The 4th byte
+	 * might have some remaining pin status. Byte 5 and 6 content
+	 * is unknown.
+	 */
+	if (rc == 6)
+		dev->gpio_last_read = le16_to_cpu(dev->gpio_buf_status);
+	else
+		rc = -EIO;
+
+	mutex_unlock(&dev->gpio_lock);
+
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+
+static int ch341_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+	int rc;
+
+	rc = read_inputs(dev);
+	if (rc)
+		return rc;
+
+	return !!(dev->gpio_last_read & BIT(offset));
+}
+
+static int ch341_gpio_get_multiple(struct gpio_chip *chip,
+				   unsigned long *mask, unsigned long *bits)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+	int rc;
+
+	rc = read_inputs(dev);
+	if (rc)
+		return rc;
+
+	*bits = dev->gpio_last_read & *mask;
+
+	return 0;
+}
+
+static void write_outputs(struct ch341_gpio *dev)
+{
+	mutex_lock(&dev->gpio_lock);
+
+	/* Only the first 6 lines can output. */
+	dev->gpio_buf[0] = CH341_CMD_UIO_STREAM;
+	dev->gpio_buf[1] = CH341_CMD_UIO_STM_DIR | (dev->gpio_dir & pin_can_output);
+	dev->gpio_buf[2] = CH341_CMD_UIO_STM_OUT |
+		(dev->gpio_last_written & dev->gpio_dir & pin_can_output);
+	dev->gpio_buf[3] = CH341_CMD_UIO_STM_END;
+
+	gpio_transfer(dev, 4, 0);
+
+	mutex_unlock(&dev->gpio_lock);
+}
+
+static void ch341_gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+
+	if (value)
+		dev->gpio_last_written |= BIT(offset);
+	else
+		dev->gpio_last_written &= ~BIT(offset);
+
+	write_outputs(dev);
+}
+
+static void ch341_gpio_set_multiple(struct gpio_chip *chip,
+				    unsigned long *mask, unsigned long *bits)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+
+	dev->gpio_last_written = (dev->gpio_last_written & ~*mask) | (*bits & *mask);
+
+	write_outputs(dev);
+}
+
+static int ch341_gpio_get_direction(struct gpio_chip *chip,
+				    unsigned int offset)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+
+	return !(dev->gpio_dir & BIT(offset));
+}
+
+static int ch341_gpio_direction_input(struct gpio_chip *chip,
+				      unsigned int offset)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+
+	dev->gpio_dir &= ~BIT(offset);
+
+	write_outputs(dev);
+
+	return 0;
+}
+
+static int ch341_gpio_direction_output(struct gpio_chip *chip,
+				       unsigned int offset, int value)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+	u16 mask = BIT(offset);
+
+	if (!(pin_can_output & mask))
+		return -EINVAL;
+
+	dev->gpio_dir |= mask;
+
+	ch341_gpio_set(chip, offset, value);
+
+	return 0;
+}
+
+static void ch341_complete_intr_urb(struct urb *urb)
+{
+	struct ch341_gpio *dev = urb->context;
+	int rc;
+
+	if (urb->status) {
+		usb_unanchor_urb(dev->irq_urb);
+	} else {
+		/*
+		 * Data is 8 bytes. Byte 0 might be the length of
+		 * significant data, which is 3 more bytes. Bytes 1
+		 * and 2, and possibly 3, are the pin status. The byte
+		 * order is different than for the GET_STATUS
+		 * command. Byte 1 is GPIOs 8 to 15, and byte 2 is
+		 * GPIOs 0 to 7.
+		 */
+
+		handle_nested_irq(irq_find_mapping(dev->gpio.irq.domain,
+						   CH341_GPIO_INT_LINE));
+
+		rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
+		if (rc)
+			usb_unanchor_urb(dev->irq_urb);
+	}
+}
+
+static int ch341_gpio_irq_set_type(struct irq_data *data, unsigned int flow_type)
+{
+	const unsigned long offset = irqd_to_hwirq(data);
+
+	if (offset != CH341_GPIO_INT_LINE || flow_type != IRQ_TYPE_EDGE_RISING)
+		return -EINVAL;
+
+	return 0;
+}
+
+static void ch341_gpio_irq_enable(struct irq_data *data)
+{
+	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
+	int rc;
+
+	/*
+	 * The URB might have just been unlinked in
+	 * ch341_gpio_irq_disable, but the completion handler hasn't
+	 * been called yet.
+	 */
+	if (!usb_wait_anchor_empty_timeout(&dev->irq_urb_out, 5000))
+		usb_kill_anchored_urbs(&dev->irq_urb_out);
+
+	usb_anchor_urb(dev->irq_urb, &dev->irq_urb_out);
+	rc = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
+	if (rc)
+		usb_unanchor_urb(dev->irq_urb);
+}
+
+static void ch341_gpio_irq_disable(struct irq_data *data)
+{
+	struct ch341_gpio *dev = irq_data_get_irq_chip_data(data);
+
+	usb_unlink_urb(dev->irq_urb);
+}
+
+static int ch341_gpio_remove(struct platform_device *pdev)
+{
+	struct ch341_gpio *dev = platform_get_drvdata(pdev);
+
+	usb_kill_anchored_urbs(&dev->irq_urb_out);
+	gpiochip_remove(&dev->gpio);
+	usb_free_urb(dev->irq_urb);
+
+	return 0;
+}
+
+static int ch341_gpio_probe(struct platform_device *pdev)
+{
+	struct ch341_device *ch341 = dev_get_drvdata(pdev->dev.parent);
+	struct gpio_irq_chip *girq;
+	struct ch341_gpio *dev;
+	struct gpio_chip *gpio;
+	int rc;
+
+	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
+	if (dev == NULL)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, dev);
+	dev->ch341 = ch341;
+	mutex_init(&dev->gpio_lock);
+
+	gpio = &dev->gpio;
+	gpio->label = dev_name(&pdev->dev);
+	gpio->parent = &pdev->dev;
+	gpio->owner = THIS_MODULE;
+	gpio->get_direction = ch341_gpio_get_direction;
+	gpio->direction_input = ch341_gpio_direction_input;
+	gpio->direction_output = ch341_gpio_direction_output;
+	gpio->get = ch341_gpio_get;
+	gpio->get_multiple = ch341_gpio_get_multiple;
+	gpio->set = ch341_gpio_set;
+	gpio->set_multiple = ch341_gpio_set_multiple;
+	gpio->base = -1;
+	gpio->ngpio = CH341_GPIO_NUM_PINS;
+	gpio->can_sleep = true;
+
+	dev->irq_chip.name = dev_name(&pdev->dev);
+	dev->irq_chip.irq_set_type = ch341_gpio_irq_set_type;
+	dev->irq_chip.irq_enable = ch341_gpio_irq_enable;
+	dev->irq_chip.irq_disable = ch341_gpio_irq_disable;
+
+	girq = &gpio->irq;
+	girq->chip = &dev->irq_chip;
+	girq->handler = handle_simple_irq;
+	girq->default_type = IRQ_TYPE_NONE;
+
+	/* Create an URB for handling interrupt */
+	dev->irq_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->irq_urb)
+		return dev_err_probe(&pdev->dev, -ENOMEM, "Cannot allocate the int URB\n");
+
+	usb_fill_int_urb(dev->irq_urb, ch341->usb_dev,
+			 usb_rcvintpipe(ch341->usb_dev, ch341->ep_intr),
+			 dev->irq_buf, CH341_USB_MAX_INTR_SIZE,
+			 ch341_complete_intr_urb, dev, ch341->ep_intr_interval);
+
+	init_usb_anchor(&dev->irq_urb_out);
+
+	rc = gpiochip_add_data(gpio, dev);
+	if (rc) {
+		rc = dev_err_probe(&pdev->dev, rc, "Could not add GPIO\n");
+		goto release_urb;
+	}
+
+	return 0;
+
+release_urb:
+	usb_free_urb(dev->irq_urb);
+
+	return rc;
+}
+
+static struct platform_driver ch341_gpio_driver = {
+	.driver.name	= "ch341-gpio",
+	.probe		= ch341_gpio_probe,
+	.remove		= ch341_gpio_remove,
+};
+module_platform_driver(ch341_gpio_driver);
+
+MODULE_AUTHOR("Various");
+MODULE_DESCRIPTION("CH341 USB to GPIO");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ch341-gpio");
diff --git a/drivers/mfd/ch341-core.c b/drivers/mfd/ch341-core.c
index 0bb6eb8057e9..e919f6901a14 100644
--- a/drivers/mfd/ch341-core.c
+++ b/drivers/mfd/ch341-core.c
@@ -19,6 +19,9 @@ 
 #include <linux/usb.h>
 
 static const struct mfd_cell ch341_devs[] = {
+	{
+		.name = "ch341-gpio",
+	},
 };
 
 static int ch341_usb_probe(struct usb_interface *iface,