[v12,0/7] Add Nuvoton NCT6694 MFD drivers

From: Ming Yu <tmyu0@nuvoton.com>

This patch series introduces support for Nuvoton NCT6694, a peripheral
expander based on USB interface. It models the chip as an MFD driver
(1/7), GPIO driver(2/7), I2C Adapter driver(3/7), CANfd driver(4/7),
WDT driver(5/7), HWMON driver(6/7), and RTC driver(7/7).

The MFD driver implements USB device functionality to issue
custom-define USB bulk pipe packets for NCT6694. Each child device can
use the USB functions nct6694_read_msg() and nct6694_write_msg() to issue
a command. They can also request interrupt that will be called when the
USB device receives its interrupt pipe.

The following introduces the custom-define USB transactions:
	nct6694_read_msg - Send bulk-out pipe to write request packet
			   Receive bulk-in pipe to read response packet
			   Receive bulk-in pipe to read data packet

	nct6694_write_msg - Send bulk-out pipe to write request packet
			    Send bulk-out pipe to write data packet
			    Receive bulk-in pipe to read response packet
			    Receive bulk-in pipe to read data packet

Changes since version 11:
- Use platform_device's id to replace IDA
- Modify the irq_domain_add_simple() to irq_domain_create_simple() in
  nct6694.c
- Update struct data_bittiming_params related part in nct6694_canfd.c
- Fix the typo in the header in nct6694-hwmon.c

Changes since version 10:
- Add change log for each patch
- Fix mfd_cell to MFD_CELL_NAME() in nct6694.c
- Implement IDA to allocate id in gpio-nct6694.c, i2c-nct6694.c,
  nct6694_canfd.c and nct6694_wdt.c
- Add header <linux/bitfield.h> in nct6694_canfd.c
- Add support to config tdc in nct6694_canfd.c
- Add module parameters to configure WDT's timeout and pretimeout value
  in nct6694_wdt.c

Changes since version 9:
- Add devm_add_action_or_reset() to dispose irq mapping
- Add KernelDoc to exported functions in nct6694.c

Changes since version 8:
- Modify the signed-off-by with my work address
- Rename all MFD cell names to "nct6694-xxx"
- Add irq_dispose_mapping() in the error handling path and in the remove
  function
- Fix some comments in nct6694.c and in nct6694.h
- Add module parameters to configure I2C's baudrate in i2c-nct6694.c
- Rename all function names nct6694_can_xxx to nct6694_canfd_xxx in
  nct6694_canfd.c
- Fix nct6694_canfd_handle_state_change() in nct6694_canfd.c
- Fix nct6694_canfd_start() to configure NBTP and DBTP in nct6694_canfd.c
- Add can_set_static_ctrlmode() in nct6694_canfd.c

Changes since version 7:
- Add error handling for devm_mutex_init()
- Modify the name of the child devices CAN1 and CAN2 to CAN0 and CAN1.
- Fix multiline comments to net-dev style in nct6694_canfd.c

Changes since version 6:
- Fix nct6694_can_handle_state_change() in nct6694_canfd.c
- Fix warnings in nct6694_canfd.c
- Move the nct6694_can_priv's bec to the end in nct6694_canfd.c
- Fix warning in nct6694_wdt.c
- Fix temp_hyst's data type to signed variable in nct6694-hwmon.c

Changes since version 5:
- Modify the module name and the driver name consistently
- Fix mfd_cell to MFD_CELL_NAME() and MFD_CELL_BASIC()
- Drop unnecessary macros in nct6694.c
- Update private data and drop mutex in nct6694_canfd.c
- Fix nct6694_can_handle_state_change() in nct6694_canfd.c

Changes since version 4:
- Modify arguments in read/write function to a pointer to cmd_header
- Modify all callers that call the read/write function
- Move the nct6694_canfd.c to drivers/net/can/usb/
- Fix the missing rx offload function in nct6694_canfd.c
- Fix warngings in nct6694-hwmon.c

Changes since version 3:
- Modify array buffer to structure for each drivers
- Fix defines and comments for each drivers
- Add header <linux/bits.h> and use BIT macro in nct6694.c and
  gpio-nct6694.c
- Modify mutex_init() to devm_mutex_init()
- Add rx-offload helper in nct6694_canfd.c
- Drop watchdog_init_timeout() in nct6694_wdt.c
- Modify the division method to DIV_ROUND_CLOSEST() in nct6694-hwmon.c
- Drop private mutex and use rtc core lock in rtc-nct6694.c
- Modify device_set_wakeup_capable() to device_init_wakeup() in
  rtc-nct6694.c

Changes since version 2:
- Add MODULE_ALIAS() for each child driver
- Modify gpio line names be a local variable in gpio-nct6694.c
- Drop unnecessary platform_get_drvdata() in gpio-nct6694.c
- Rename each command in nct6694_canfd.c
- Modify each function name consistently in nct6694_canfd.c
- Modify the pretimeout validation procedure in nct6694_wdt.c
- Fix warnings in nct6694-hwmon.c

Changes since version 1:
- Implement IRQ domain to handle IRQ demux in nct6694.c
- Modify USB_DEVICE to USB_DEVICE_AND_INTERFACE_INFO API in nct6694.c
- Add each driver's command structure
- Fix USB functions in nct6694.c
- Fix platform driver registration in each child driver
- Sort each driver's header files alphabetically
- Drop unnecessary header in gpio-nct6694.c
- Add gpio line names in gpio-nct6694.c
- Fix errors and warnings in nct6694_canfd.c
- Fix TX-flow control in nct6694_canfd.c
- Fix warnings in nct6694_wdt.c
- Drop unnecessary logs in nct6694_wdt.c
- Modify start() function to setup device in nct6694_wdt.c
- Add voltage sensors functionality in nct6694-hwmon.c
- Add temperature sensors functionality in nct6694-hwmon.c
- Fix overwrite error return values in nct6694-hwmon.c
- Add write value limitation for each write() function in nct6694-hwmon.c
- Drop unnecessary logs in rtc-nct6694.c
- Fix overwrite error return values in rtc-nct6694.c
- Modify to use dev_err_probe API in rtc-nct6694.c


Ming Yu (7):
  mfd: Add core driver for Nuvoton NCT6694
  gpio: Add Nuvoton NCT6694 GPIO support
  i2c: Add Nuvoton NCT6694 I2C support
  can: Add Nuvoton NCT6694 CANFD support
  watchdog: Add Nuvoton NCT6694 WDT support
  hwmon: Add Nuvoton NCT6694 HWMON support
  rtc: Add Nuvoton NCT6694 RTC support

 MAINTAINERS                         |  12 +
 drivers/gpio/Kconfig                |  12 +
 drivers/gpio/Makefile               |   1 +
 drivers/gpio/gpio-nct6694.c         | 479 ++++++++++++++
 drivers/hwmon/Kconfig               |  10 +
 drivers/hwmon/Makefile              |   1 +
 drivers/hwmon/nct6694-hwmon.c       | 949 ++++++++++++++++++++++++++++
 drivers/i2c/busses/Kconfig          |  10 +
 drivers/i2c/busses/Makefile         |   1 +
 drivers/i2c/busses/i2c-nct6694.c    | 174 +++++
 drivers/mfd/Kconfig                 |  15 +
 drivers/mfd/Makefile                |   2 +
 drivers/mfd/nct6694.c               | 386 +++++++++++
 drivers/net/can/usb/Kconfig         |  11 +
 drivers/net/can/usb/Makefile        |   1 +
 drivers/net/can/usb/nct6694_canfd.c | 820 ++++++++++++++++++++++++
 drivers/rtc/Kconfig                 |  10 +
 drivers/rtc/Makefile                |   1 +
 drivers/rtc/rtc-nct6694.c           | 297 +++++++++
 drivers/watchdog/Kconfig            |  11 +
 drivers/watchdog/Makefile           |   1 +
 drivers/watchdog/nct6694_wdt.c      | 291 +++++++++
 include/linux/mfd/nct6694.h         |  98 +++
 23 files changed, 3593 insertions(+)
 create mode 100644 drivers/gpio/gpio-nct6694.c
 create mode 100644 drivers/hwmon/nct6694-hwmon.c
 create mode 100644 drivers/i2c/busses/i2c-nct6694.c
 create mode 100644 drivers/mfd/nct6694.c
 create mode 100644 drivers/net/can/usb/nct6694_canfd.c
 create mode 100644 drivers/rtc/rtc-nct6694.c
 create mode 100644 drivers/watchdog/nct6694_wdt.c
 create mode 100644 include/linux/mfd/nct6694.h

Dear Oliver,

Thank you for reviewing,

Oliver Neukum <oneukum@suse.com> 於 2025年6月4日 週三 下午6:11寫道：
>
> > +static void usb_int_callback(struct urb *urb)
> > +{
> > +     struct nct6694 *nct6694 = urb->context;
> > +     unsigned int *int_status = urb->transfer_buffer;
> > +     int ret;
> > +
> > +     switch (urb->status) {
> > +     case 0:
> > +             break;
> > +     case -ECONNRESET:
> > +     case -ENOENT:
> > +     case -ESHUTDOWN:
> > +             return;
> > +     default:
> > +             goto resubmit;
> > +     }
> > +
> > +     while (*int_status) {
> > +             int irq = __ffs(*int_status);
> > +
> > +             generic_handle_irq_safe(irq_find_mapping(nct6694->domain, irq));
> > +             *int_status &= ~BIT(irq);
> > +     }
>
> Does modifying the byte have any benefit?
>

I will update the code in the next patch to use __le32 for the
variable to ensure proper endianness handling across architectures.

> > +resubmit:
> > +     ret = usb_submit_urb(urb, GFP_ATOMIC);
> > +     if (ret)
> > +             dev_warn(nct6694->dev, "Failed to resubmit urb, status %pe",  ERR_PTR(ret));
> > +}
> > +
> > +static void nct6694_irq_lock(struct irq_data *data)
> > +{
> > +     struct nct6694 *nct6694 = irq_data_get_irq_chip_data(data);
> > +
> > +     mutex_lock(&nct6694->irq_lock);
> > +}
>
> Why? Does this do anything but make it _harder_ to tell that you
> cannot take the lock in interrupt?
>

I plan to remove nct6694_irq_lock() and nct6694_bus_sync_unlock(), and
instead add the spinlock directly inside the function like this:
static void nct6694_irq_enable(struct irq_data *data)
{
    ...
    spin_lock(&nct6694->irq_lock);
    nct6694->irq_enable |= BIT(hwirq);
    spin_unlock(&nct6694->irq_lock);
}

Do you think this approach is better?


Best regards,
Ming