Message-ID: <CAMRc=Mc+49C+GftT02HptPKYnrL+QidSB9fH2GC4yPecHqW4dQ@mail.gmail.com>
Date: Tue, 1 Oct 2024 21:04:58 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Mary Strodl <mstrodl@....rit.edu>
Cc: linux-kernel@...r.kernel.org, linus.walleij@...aro.org, 
	linux-gpio@...r.kernel.org
Subject: Re: [PATCH v3] gpio: add support for FTDI's MPSSE as GPIO

On Thu, Sep 26, 2024 at 2:44 PM Mary Strodl <mstrodl@....rit.edu> wrote:
>
> FTDI FT2232H is a USB to GPIO chip. Sealevel produces some devices
> with this chip. FT2232H presents itself as a composite device with two
> interfaces (each is an "MPSSE"). Each MPSSE has two banks (high and low)
> of 8 GPIO each. I believe some MPSSE's have only one bank, but I don't
> know how to identify them (I don't have any for testing) and as a result
> are unsupported for the time being.
>
> Additionally, this driver provides software polling-based interrupts for
> edge detection. For the Sealevel device I have to test with, this works
> well because there is hardware debouncing. From talking to Sealevel's
> people, this is their preferred way to do edge detection.
>
> Signed-off-by: Mary Strodl <mstrodl@....rit.edu>
> ---
>
> Changes since last time:
> * Switch to linux/cleanup.h mutex guards
> * Use defines for GPIO_LINE_DIRECTION
> * Skip the polling loop if get_multiple fails
> * Remove unneeded `irq_domain_remove` call, it's no longer managed externally
>
>  drivers/gpio/Kconfig      |   7 +
>  drivers/gpio/Makefile     |   1 +
>  drivers/gpio/gpio-mpsse.c | 522 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 530 insertions(+)
>  create mode 100644 drivers/gpio/gpio-mpsse.c
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index d93cd4f722b4..cbe3baa1b3de 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -1844,6 +1844,13 @@ config GPIO_VIPERBOARD
>           River Tech's viperboard.h for detailed meaning
>           of the module parameters.
>
> +config GPIO_MPSSE
> +       tristate "FTDI MPSSE GPIO support"
> +       select GPIOLIB_IRQCHIP
> +       help
> +         GPIO driver for FTDI's MPSSE interface. These can do input and
> +         output. Each MPSSE provides 16 IO pins.
> +
>  endmenu
>
>  menu "Virtual GPIO drivers"
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index 1429e8c0229b..cc5d5519ba4b 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -114,6 +114,7 @@ obj-$(CONFIG_GPIO_MOCKUP)           += gpio-mockup.o
>  obj-$(CONFIG_GPIO_MOXTET)              += gpio-moxtet.o
>  obj-$(CONFIG_GPIO_MPC5200)             += gpio-mpc5200.o
>  obj-$(CONFIG_GPIO_MPC8XXX)             += gpio-mpc8xxx.o
> +obj-$(CONFIG_GPIO_MPSSE)               += gpio-mpsse.o
>  obj-$(CONFIG_GPIO_MSC313)              += gpio-msc313.o
>  obj-$(CONFIG_GPIO_MT7621)              += gpio-mt7621.o
>  obj-$(CONFIG_GPIO_MVEBU)               += gpio-mvebu.o
> diff --git a/drivers/gpio/gpio-mpsse.c b/drivers/gpio/gpio-mpsse.c
> new file mode 100644
> index 000000000000..cf63178135c7
> --- /dev/null
> +++ b/drivers/gpio/gpio-mpsse.c
> @@ -0,0 +1,522 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * FTDI MPSSE GPIO support
> + *
> + * Based on code by Anatolij Gustschin
> + *
> + * Copyright (C) 2024 Mary Strodl <mstrodl@....rit.edu>
> + */
> +
> +#include <linux/cleanup.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/mutex.h>
> +#include <linux/usb.h>
> +
> +struct mpsse_priv {
> +       struct gpio_chip gpio;
> +       struct usb_device *udev;     /* USB device encompassing all MPSSEs */
> +       struct usb_interface *intf;  /* USB interface for this MPSSE */
> +       u8 intf_id;                  /* USB interface number for this MPSSE */
> +       struct work_struct irq_work; /* polling work thread */
> +       struct mutex irq_mutex;      /* lock over irq_data */
> +       atomic_t irq_type[16];       /* pin -> edge detection type */
> +       atomic_t irq_enabled;
> +       int id;
> +
> +       u8 gpio_outputs[2];          /* Output states for GPIOs [L, H] */
> +       u8 gpio_dir[2];              /* Directions for GPIOs [L, H] */
> +
> +       u8 *bulk_in_buf;             /* Extra recv buffer to grab status bytes */
> +
> +       struct usb_endpoint_descriptor *bulk_in;
> +       struct usb_endpoint_descriptor *bulk_out;
> +
> +       struct mutex io_mutex;      /* sync I/O with disconnect */
> +};
> +
> +struct bulk_desc {
> +       bool tx;                    /* direction of bulk transfer */
> +       u8 *data;                   /* input (tx) or output (rx) */
> +       int len;                    /* Length of `data` if tx, or length of */
> +                                   /* Data to read if rx */
> +       int len_actual;             /* Length successfully transferred */
> +       int timeout;
> +};
> +
> +static const struct usb_device_id gpio_mpsse_table[] = {
> +       { USB_DEVICE(0x0c52, 0xa064) },   /* SeaLevel Systems, Inc. */
> +       { }                               /* Terminating entry */
> +};

I don't know much about the USB subsystem in the kernel, maybe Cc Greg
KH on this?

> +
> +MODULE_DEVICE_TABLE(usb, gpio_mpsse_table);
> +
> +static DEFINE_IDA(gpio_mpsse_ida);
> +
> +/* MPSSE commands */
> +#define SET_BITS_CMD 0x80
> +#define GET_BITS_CMD 0x81
> +
> +#define SET_BITMODE_REQUEST 0x0B
> +#define MODE_MPSSE (2 << 8)
> +#define MODE_RESET 0
> +
> +/* Arbitrarily decided. This could probably be much less */
> +#define MPSSE_WRITE_TIMEOUT 5000
> +#define MPSSE_READ_TIMEOUT 5000
> +
> +/* 1 millisecond, also pretty arbitrary */
> +#define MPSSE_POLL_INTERVAL 1000
> +
> +static int mpsse_bulk_xfer(struct usb_interface *intf, struct bulk_desc *desc)
> +{
> +       struct mpsse_priv *priv = usb_get_intfdata(intf);
> +       struct usb_device *udev = priv->udev;
> +       unsigned int pipe;
> +       int ret;
> +
> +       if (desc->tx)
> +               pipe = usb_sndbulkpipe(udev, priv->bulk_out->bEndpointAddress);
> +       else
> +               pipe = usb_rcvbulkpipe(udev, priv->bulk_in->bEndpointAddress);
> +
> +       ret = usb_bulk_msg(udev, pipe, desc->data, desc->len,
> +                          &desc->len_actual, desc->timeout);
> +       if (ret)
> +               dev_dbg(&udev->dev, "mpsse: bulk transfer failed: %d\n", ret);
> +
> +       return ret;
> +}
> +
> +static int mpsse_write(struct usb_interface *intf,
> +                      u8 *buf, size_t len)
> +{
> +       int ret;
> +       struct bulk_desc desc;
> +
> +       desc.len_actual = 0;
> +       desc.tx = true;
> +       desc.data = buf;
> +       desc.len = len;
> +       desc.timeout = MPSSE_WRITE_TIMEOUT;
> +
> +       ret = mpsse_bulk_xfer(intf, &desc);
> +
> +       return ret;
> +}
> +
> +static int mpsse_read(struct usb_interface *intf, u8 *buf, size_t len)
> +{
> +       int ret;
> +       struct bulk_desc desc;
> +       struct mpsse_priv *priv = usb_get_intfdata(intf);
> +
> +       desc.len_actual = 0;
> +       desc.tx = false;
> +       desc.data = priv->bulk_in_buf;
> +       /* Device sends 2 additional status bytes, read len + 2 */
> +       desc.len = min_t(size_t, len + 2, usb_endpoint_maxp(priv->bulk_in));
> +       desc.timeout = MPSSE_READ_TIMEOUT;
> +
> +       ret = mpsse_bulk_xfer(intf, &desc);
> +       if (ret)
> +               return ret;
> +
> +       /* Did we get enough data? */
> +       if (desc.len_actual < desc.len)
> +               return -EIO;
> +
> +       memcpy(buf, desc.data + 2, desc.len_actual - 2);
> +
> +       return ret;
> +}
> +
> +static int gpio_mpsse_set_bank(struct mpsse_priv *priv, u8 bank)
> +{
> +       int ret;
> +       u8 tx_buf[3] = {
> +               SET_BITS_CMD | (bank << 1),
> +               priv->gpio_outputs[bank],
> +               priv->gpio_dir[bank],
> +       };
> +
> +       ret = mpsse_write(priv->intf, tx_buf, 3);
> +
> +       return ret;
> +}
> +
> +static int gpio_mpsse_get_bank(struct mpsse_priv *priv, u8 bank)
> +{
> +       int ret;
> +       u8 buf = GET_BITS_CMD | (bank << 1);
> +
> +       ret = mpsse_write(priv->intf, &buf, 1);
> +       if (ret)
> +               return ret;
> +
> +       ret = mpsse_read(priv->intf, &buf, 1);
> +       if (ret)
> +               return ret;
> +
> +       return buf;
> +}
> +
> +static void gpio_mpsse_set_multiple(struct gpio_chip *chip, unsigned long *mask,
> +                                   unsigned long *bits)
> +{
> +       unsigned long i, bank, bank_mask, bank_bits;
> +       int ret;
> +       struct mpsse_priv *priv = gpiochip_get_data(chip);
> +
> +       guard(mutex)(&priv->io_mutex);
> +       for_each_set_clump8(i, bank_mask, mask, chip->ngpio) {
> +               bank = i / 8;
> +
> +               if (bank_mask) {
> +                       bank_bits = bitmap_get_value8(bits, i);
> +                       /* Zero out pins we want to change */
> +                       priv->gpio_outputs[bank] &= ~bank_mask;
> +                       /* Set pins we care about */
> +                       priv->gpio_outputs[bank] |= bank_bits & bank_mask;
> +
> +                       ret = gpio_mpsse_set_bank(priv, bank);
> +                       if (ret)
> +                               dev_err(&priv->intf->dev,
> +                                       "Couldn't set values for bank %ld!",
> +                                       bank);
> +               }
> +       }
> +}
> +
> +static int gpio_mpsse_get_multiple(struct gpio_chip *chip, unsigned long *mask,
> +                                  unsigned long *bits)
> +{
> +       unsigned long i, bank, bank_mask;
> +       int ret;
> +       struct mpsse_priv *priv = gpiochip_get_data(chip);
> +
> +       guard(mutex)(&priv->io_mutex);
> +       for_each_set_clump8(i, bank_mask, mask, chip->ngpio) {
> +               bank = i / 8;
> +
> +               if (bank_mask) {
> +                       ret = gpio_mpsse_get_bank(priv, bank);
> +                       if (ret < 0)
> +                               return ret;
> +
> +                       bitmap_set_value8(bits, ret & bank_mask, i);
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +static int gpio_mpsse_gpio_get(struct gpio_chip *chip, unsigned int offset)
> +{
> +       int err;
> +       unsigned long mask = 0, bits = 0;
> +
> +       __set_bit(offset, &mask);
> +       err = gpio_mpsse_get_multiple(chip, &mask, &bits);
> +       if (err)
> +               return err;
> +
> +       /* == is not guaranteed to give 1 if true */
> +       if (bits)
> +               return 1;
> +       else
> +               return 0;
> +}
> +
> +static void gpio_mpsse_gpio_set(struct gpio_chip *chip, unsigned int offset,
> +                              int value)
> +{
> +       unsigned long mask = 0, bits = 0;
> +
> +       __set_bit(offset, &mask);
> +       if (value)
> +               __set_bit(offset, &bits);
> +
> +       gpio_mpsse_set_multiple(chip, &mask, &bits);
> +}
> +
> +static int gpio_mpsse_direction_output(struct gpio_chip *chip,
> +                                      unsigned int offset, int value)
> +{
> +       struct mpsse_priv *priv = gpiochip_get_data(chip);
> +       int bank = (offset & 8) >> 3;
> +       int bank_offset = offset & 7;
> +
> +       scoped_guard(mutex, &priv->io_mutex)
> +               priv->gpio_dir[bank] |= BIT(bank_offset);

Add a newline here.

> +       gpio_mpsse_gpio_set(chip, offset, value);
> +
> +       return 0;
> +}
> +
> +static int gpio_mpsse_direction_input(struct gpio_chip *chip,
> +                                     unsigned int offset)
> +{
> +       struct mpsse_priv *priv = gpiochip_get_data(chip);
> +       int bank = (offset & 8) >> 3;
> +       int bank_offset = offset & 7;
> +
> +       guard(mutex)(&priv->io_mutex);
> +       priv->gpio_dir[bank] &= ~BIT(bank_offset);
> +       gpio_mpsse_set_bank(priv, bank);
> +
> +       return 0;
> +}
> +
> +static int gpio_mpsse_get_direction(struct gpio_chip *chip,
> +                                   unsigned int offset)
> +{
> +       int ret;
> +       int bank = (offset & 8) >> 3;
> +       int bank_offset = offset & 7;
> +       struct mpsse_priv *priv = gpiochip_get_data(chip);
> +
> +       guard(mutex)(&priv->io_mutex);
> +       /* MPSSE directions are inverted */
> +       if (priv->gpio_dir[bank] & BIT(bank_offset))
> +               ret = GPIO_LINE_DIRECTION_OUT;
> +       else
> +               ret = GPIO_LINE_DIRECTION_IN;
> +
> +       return ret;
> +}
> +
> +static void gpio_mpsse_poll(struct work_struct *work)
> +{
> +       unsigned long pin_mask, pin_states, flags;
> +       int irq_enabled, offset, err, value, fire_irq,
> +               irq, old_value[16], irq_type[16];
> +       struct mpsse_priv *priv = container_of(work, struct mpsse_priv,
> +                                              irq_work);
> +
> +       for (offset = 0; offset < priv->gpio.ngpio; ++offset)
> +               old_value[offset] = -1;
> +
> +       while ((irq_enabled = atomic_read(&priv->irq_enabled))) {
> +               usleep_range(MPSSE_POLL_INTERVAL, MPSSE_POLL_INTERVAL + 1000);
> +               /* Cleanup will trigger at the end of the loop */
> +               guard(mutex)(&priv->irq_mutex);
> +
> +               pin_mask = 0;
> +               pin_states = 0;
> +               for (offset = 0; offset < priv->gpio.ngpio; ++offset) {
> +                       irq_type[offset] = atomic_read(&priv->irq_type[offset]);
> +                       if (irq_type[offset] != IRQ_TYPE_NONE &&
> +                           irq_enabled & BIT(offset))
> +                               pin_mask |= BIT(offset);
> +                       else
> +                               old_value[offset] = -1;
> +               }
> +
> +               err = gpio_mpsse_get_multiple(&priv->gpio, &pin_mask,
> +                                             &pin_states);
> +               if (err) {
> +                       dev_err_ratelimited(&priv->intf->dev,
> +                                           "Error polling!\n");
> +                       continue;
> +               }
> +
> +               /* Check each value */
> +               for (offset = 0; offset < priv->gpio.ngpio; ++offset) {
> +                       if (old_value[offset] == -1)
> +                               continue;
> +
> +                       fire_irq = 0;
> +                       value = pin_states & BIT(offset);
> +
> +                       switch (irq_type[offset]) {
> +                       case IRQ_TYPE_EDGE_RISING:
> +                               fire_irq = value > old_value[offset];
> +                               break;
> +                       case IRQ_TYPE_EDGE_FALLING:
> +                               fire_irq = value < old_value[offset];
> +                               break;
> +                       case IRQ_TYPE_EDGE_BOTH:
> +                               fire_irq = value != old_value[offset];
> +                               break;
> +                       }
> +                       if (!fire_irq)
> +                               continue;
> +
> +                       irq = irq_find_mapping(priv->gpio.irq.domain,
> +                                              offset);
> +                       local_irq_save(flags);
> +                       generic_handle_irq(irq);
> +                       local_irq_disable();
> +                       local_irq_restore(flags);
> +               }
> +
> +               /* Sync back values so we can refer to them next tick */
> +               for (offset = 0; offset < priv->gpio.ngpio; ++offset)
> +                       if (irq_type[offset] != IRQ_TYPE_NONE &&
> +                           irq_enabled & BIT(offset))
> +                               old_value[offset] = pin_states & BIT(offset);
> +       }
> +}
> +
> +static int gpio_mpsse_set_irq_type(struct irq_data *irqd, unsigned int type)
> +{
> +       int offset;
> +       struct mpsse_priv *priv = irq_data_get_irq_chip_data(irqd);
> +
> +       offset = irqd->hwirq;
> +       atomic_set(&priv->irq_type[offset], type & IRQ_TYPE_EDGE_BOTH);
> +
> +       return 0;
> +}
> +
> +static void gpio_mpsse_irq_disable(struct irq_data *irqd)
> +{
> +       struct mpsse_priv *priv = irq_data_get_irq_chip_data(irqd);
> +
> +       atomic_and(~BIT(irqd->hwirq), &priv->irq_enabled);
> +       gpiochip_disable_irq(&priv->gpio, irqd->hwirq);
> +}
> +
> +static void gpio_mpsse_irq_enable(struct irq_data *irqd)
> +{
> +       struct mpsse_priv *priv = irq_data_get_irq_chip_data(irqd);
> +
> +       gpiochip_enable_irq(&priv->gpio, irqd->hwirq);
> +       /* If no-one else was using the IRQ, enable it */
> +       if (!atomic_fetch_or(BIT(irqd->hwirq), &priv->irq_enabled)) {
> +               INIT_WORK(&priv->irq_work, gpio_mpsse_poll);
> +               schedule_work(&priv->irq_work);
> +       }
> +}
> +
> +static const struct irq_chip gpio_mpsse_irq_chip = {
> +       .name = "gpio-mpsse-irq",
> +       .irq_enable = gpio_mpsse_irq_enable,
> +       .irq_disable = gpio_mpsse_irq_disable,
> +       .irq_set_type = gpio_mpsse_set_irq_type,
> +       .flags = IRQCHIP_IMMUTABLE,
> +       GPIOCHIP_IRQ_RESOURCE_HELPERS,
> +};
> +
> +static int gpio_mpsse_probe(struct usb_interface *interface,
> +                           const struct usb_device_id *id)
> +{
> +       struct mpsse_priv *priv;
> +       struct device *dev;
> +       int err;
> +
> +       dev = &interface->dev;
> +       priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +       if (!priv)
> +               return -ENOMEM;
> +
> +       priv->udev = usb_get_dev(interface_to_usbdev(interface));
> +       priv->intf = interface;
> +       priv->intf_id = interface->cur_altsetting->desc.bInterfaceNumber;
> +
> +       priv->id = ida_simple_get(&gpio_mpsse_ida, 0, 0, GFP_KERNEL);
> +       if (priv->id < 0)
> +               return priv->id;
> +
> +       devm_mutex_init(dev, &priv->io_mutex);
> +       devm_mutex_init(dev, &priv->irq_mutex);
> +
> +       priv->gpio.label = devm_kasprintf(dev, GFP_KERNEL,
> +                                         "gpio-mpsse.%d.%d",
> +                                         priv->id, priv->intf_id);
> +       if (!priv->gpio.label) {
> +               err = -ENOMEM;
> +               goto err;
> +       }
> +
> +       priv->gpio.owner = THIS_MODULE;
> +       priv->gpio.parent = interface->usb_dev;
> +       priv->gpio.get_direction = gpio_mpsse_get_direction;
> +       priv->gpio.direction_input = gpio_mpsse_direction_input;
> +       priv->gpio.direction_output = gpio_mpsse_direction_output;
> +       priv->gpio.get = gpio_mpsse_gpio_get;
> +       priv->gpio.set = gpio_mpsse_gpio_set;
> +       priv->gpio.get_multiple = gpio_mpsse_get_multiple;
> +       priv->gpio.set_multiple = gpio_mpsse_set_multiple;
> +       priv->gpio.base = -1;
> +       priv->gpio.ngpio = 16;
> +       priv->gpio.offset = priv->intf_id * priv->gpio.ngpio;
> +       priv->gpio.can_sleep = 1;
> +
> +       err = usb_find_common_endpoints(interface->cur_altsetting,
> +                                       &priv->bulk_in, &priv->bulk_out,
> +                                       NULL, NULL);
> +       if (err)
> +               goto err;
> +
> +       priv->bulk_in_buf = devm_kmalloc(dev, usb_endpoint_maxp(priv->bulk_in),
> +                                        GFP_KERNEL);
> +       if (!priv->bulk_in_buf) {
> +               err = -ENOMEM;
> +               goto err;
> +       }
> +
> +       usb_set_intfdata(interface, priv);
> +

Stray newline

> +
> +       /* Reset mode, needed to correctly enter MPSSE mode */
> +       err = usb_control_msg(priv->udev, usb_sndctrlpipe(priv->udev, 0),
> +                             SET_BITMODE_REQUEST,
> +                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
> +                             MODE_RESET, priv->intf_id + 1, NULL, 0,
> +                             USB_CTRL_SET_TIMEOUT);
> +       if (err)
> +               goto err;
> +
> +       /* Enter MPSSE mode */
> +       err = usb_control_msg(priv->udev, usb_sndctrlpipe(priv->udev, 0),
> +                             SET_BITMODE_REQUEST,
> +                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
> +                             MODE_MPSSE, priv->intf_id + 1, NULL, 0,
> +                             USB_CTRL_SET_TIMEOUT);
> +       if (err)
> +               goto err;
> +
> +       gpio_irq_chip_set_chip(&priv->gpio.irq, &gpio_mpsse_irq_chip);
> +
> +       priv->gpio.irq.parent_handler = NULL;
> +       priv->gpio.irq.num_parents = 0;
> +       priv->gpio.irq.parents = NULL;
> +       priv->gpio.irq.default_type = IRQ_TYPE_NONE;
> +       priv->gpio.irq.handler = handle_simple_irq;
> +
> +       err = devm_gpiochip_add_data(dev, &priv->gpio, priv);
> +       if (err)
> +               goto err;
> +
> +       return 0;
> +
> +err:
> +       ida_simple_remove(&gpio_mpsse_ida, priv->id);
> +

You could drop this label, all the gotos and the corresponding free in
remove if you scheduled a devm action with devm_add_action_or_reset()
right after getting the new index.

> +       return err;
> +}
> +
> +static void gpio_mpsse_disconnect(struct usb_interface *intf)
> +{
> +       struct mpsse_priv *priv = usb_get_intfdata(intf);
> +
> +       ida_simple_remove(&gpio_mpsse_ida, priv->id);
> +
> +       priv->intf = NULL;
> +       usb_set_intfdata(intf, NULL);
> +       usb_put_dev(priv->udev);
> +}
> +
> +static struct usb_driver gpio_mpsse_driver = {
> +       .name           = "gpio-mpsse",
> +       .probe          = gpio_mpsse_probe,
> +       .disconnect     = gpio_mpsse_disconnect,
> +       .id_table       = gpio_mpsse_table,
> +};
> +
> +module_usb_driver(gpio_mpsse_driver);
> +
> +MODULE_AUTHOR("Mary Strodl <mstrodl@....rit.edu>");
> +MODULE_DESCRIPTION("MPSSE GPIO driver");
> +MODULE_LICENSE("GPL");
> --
> 2.45.2
>

Overall it looks clean and nice but I can't tell if the USB-specific
bits are correct.

Bart

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