Date:   Wed, 15 Jun 2022 20:37:45 -0500
From:   frank zago <frank@...o.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Wolfram Sang <wsa@...nel.org>, Johan Hovold <johan@...nel.org>,
        linux-usb@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        frank zago <frank@...o.net>
Subject: [PATCH v6 2/4] gpio: ch341: add GPIO MFD cell driver for the CH341

The GPIO interface offers 16 GPIOs. 6 are read/write, and 10 are
read-only.

Signed-off-by: frank zago <frank@...o.net>
---
 MAINTAINERS               |   1 +
 drivers/gpio/Kconfig      |  10 +
 drivers/gpio/Makefile     |   1 +
 drivers/gpio/gpio-ch341.c | 385 ++++++++++++++++++++++++++++++++++++++
 include/linux/mfd/ch341.h |   8 +
 5 files changed, 405 insertions(+)
 create mode 100644 drivers/gpio/gpio-ch341.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 628eeaa9bf68..8b93f6192704 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21479,6 +21479,7 @@ WINCHIPHEAD CH341 I2C/GPIO MFD DRIVER
 M:	Frank Zago <frank@...o.net>
 L:	linux-usb@...r.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 b01961999ced..473b6e7226ca 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1653,6 +1653,16 @@ 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..233dfe1f2ae8
--- /dev/null
+++ b/drivers/gpio/gpio-ch341.c
@@ -0,0 +1,385 @@
+// 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@...orcht.net)
+ * Copyright (c) 2016 Tse Lun Bien
+ * Copyright (c) 2014 Marco Gittler
+ * Copyright (c) 2006-2007 Till Harbaum (Till@...baum.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/gpio/driver.h>
+#include <linux/kernel.h>
+#include <linux/mfd/ch341.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/usb.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_ddata *ddata;
+};
+
+/*
+ * 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_ddata *ddata = dev->ddata;
+	int actual;
+	int ret;
+
+	mutex_lock(&ddata->usb_lock);
+
+	ret = usb_bulk_msg(ddata->usb_dev,
+			   usb_sndbulkpipe(ddata->usb_dev, ddata->ep_out),
+			   dev->gpio_buf, out_len,
+			   &actual, DEFAULT_TIMEOUT_MS);
+	if (ret < 0)
+		goto out_unlock;
+
+	if (in_len == 0)
+		goto out_unlock;
+
+	ret = usb_bulk_msg(ddata->usb_dev,
+			   usb_rcvbulkpipe(ddata->usb_dev, ddata->ep_in),
+			   dev->gpio_buf, SEG_SIZE, &actual, DEFAULT_TIMEOUT_MS);
+
+out_unlock:
+	mutex_unlock(&ddata->usb_lock);
+
+	if (ret < 0)
+		return ret;
+
+	return actual;
+}
+
+/* Read the GPIO line status. */
+static int read_inputs(struct ch341_gpio *dev)
+{
+	int ret;
+
+	mutex_lock(&dev->gpio_lock);
+
+	dev->gpio_buf[0] = CH341_PARA_CMD_STS;
+
+	ret = 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 (ret == 6)
+		dev->gpio_last_read = le16_to_cpu(dev->gpio_buf_status);
+	else
+		ret = -EIO;
+
+	mutex_unlock(&dev->gpio_lock);
+
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int ch341_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct ch341_gpio *dev = gpiochip_get_data(chip);
+	int ret;
+
+	ret = read_inputs(dev);
+	if (ret)
+		return ret;
+
+	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 ret;
+
+	ret = read_inputs(dev);
+	if (ret)
+		return ret;
+
+	*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 ret;
+
+	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));
+
+		ret = usb_submit_urb(dev->irq_urb, GFP_ATOMIC);
+		if (ret)
+			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 ret;
+
+	/*
+	 * 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);
+	ret = usb_submit_urb(dev->irq_urb, GFP_KERNEL);
+	if (ret)
+		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 const struct irq_chip ch341_irqchip = {
+	.name = "CH341",
+	.irq_set_type = ch341_gpio_irq_set_type,
+	.irq_enable = ch341_gpio_irq_enable,
+	.irq_disable = ch341_gpio_irq_disable,
+	.flags = IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
+};
+
+static int ch341_gpio_probe(struct platform_device *pdev)
+{
+	struct ch341_ddata *ddata = dev_get_drvdata(pdev->dev.parent);
+	struct gpio_irq_chip *girq;
+	struct ch341_gpio *dev;
+	struct gpio_chip *gpio;
+	int ret;
+
+	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
+	if (dev == NULL)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, dev);
+	dev->ddata = ddata;
+	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;
+
+	girq = &gpio->irq;
+	gpio_irq_chip_set_chip(girq, &ch341_irqchip);
+	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, ddata->usb_dev,
+			 usb_rcvintpipe(ddata->usb_dev, ddata->ep_intr),
+			 dev->irq_buf, CH341_USB_MAX_INTR_SIZE,
+			 ch341_complete_intr_urb, dev, ddata->ep_intr_interval);
+
+	init_usb_anchor(&dev->irq_urb_out);
+
+	ret = gpiochip_add_data(gpio, dev);
+	if (ret) {
+		ret = dev_err_probe(&pdev->dev, ret, "Could not add GPIO\n");
+		goto release_urb;
+	}
+
+	return 0;
+
+release_urb:
+	usb_free_urb(dev->irq_urb);
+
+	return ret;
+}
+
+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("Frank Zago <frank@...o.net>");
+MODULE_DESCRIPTION("CH341 USB to GPIO");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ch341-gpio");
diff --git a/include/linux/mfd/ch341.h b/include/linux/mfd/ch341.h
index 44f5da0720bd..804d671fbe45 100644
--- a/include/linux/mfd/ch341.h
+++ b/include/linux/mfd/ch341.h
@@ -4,6 +4,14 @@
 #include <linux/mutex.h>
 #include <linux/types.h>
 
+#define DEFAULT_TIMEOUT_MS 1000	/* 1s USB requests timeout */
+
+/*
+ * All commands fit inside a 32-byte segment. There may be several of
+ * these segments in a USB command.
+ */
+#define SEG_SIZE 32
+
 struct usb_device;
 struct usb_interface;
 
-- 
2.32.0

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