[V4,1/3] mfd: Add support for UP board CPLD/FPGA

The UP Squared board <http://www.upboard.com> implements certain
features (pin control, onboard LEDs or CEC) through an on-board CPLD/FPGA.

This mfd driver implements the line protocol to read and write registers
from the FPGA through regmap. The register address map is also included.

The UP Boards provide a few I/O pin headers (for both GPIO and
functions), including a 40-pin Raspberry Pi compatible header.

This patch implements support for the FPGA-based pin controller that
manages direction and enable state for those header pins.

Partial support UP boards:
* UP core + CREX
* UP core + CRST02

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: larry.lai <larry.lai@yunjingtech.com>
---
RFC 2023/04/25 -> PATCH V4
(1) Fixed kernel test robot compiler warning.
(2) Remove mistakes with wrong Reviewed-by tags.
RFC 2022/11/23 -> RFC 2023/04/25
(1) Refer 2022/12/08 Andy Shevchenko review, cleaned up coding style
and addressed review comments.
PATCH V3 -> RFC 2022/11/23:
(1) Refer 2022/11/16 Lee Jones review, cleaned up coding style and
addressed review comments.
(2) Description on the UP Boards FPGA register read/write protocols
PATCH V2 -> V3:
(1) fixed kernel test robot compiler warning.
PATCH V1 -> V2:
(1) Synchronizing upboard github to rc2
(2) Refer 2022/10/31 Lee Jones review, fixed some of the issues.
---
 drivers/mfd/Kconfig              |  12 +
 drivers/mfd/Makefile             |   1 +
 drivers/mfd/upboard-fpga.c       | 526 +++++++++++++++++++++++++++++++
 include/linux/mfd/upboard-fpga.h |  61 ++++
 4 files changed, 600 insertions(+)
 create mode 100644 drivers/mfd/upboard-fpga.c
 create mode 100644 include/linux/mfd/upboard-fpga.h

On Thu, 11 May 2023, larry.lai wrote:

> The UP Squared board <http://www.upboard.com> implements certain
> features (pin control, onboard LEDs or CEC) through an on-board CPLD/FPGA.
> 
> This mfd driver implements the line protocol to read and write registers

Drop all mentions of MFD from commit logs and comments.

MFD is not a real thing.  Please only describe the device.

> from the FPGA through regmap. The register address map is also included.
> 
> The UP Boards provide a few I/O pin headers (for both GPIO and
> functions), including a 40-pin Raspberry Pi compatible header.
> 
> This patch implements support for the FPGA-based pin controller that
> manages direction and enable state for those header pins.
> 
> Partial support UP boards:
> * UP core + CREX
> * UP core + CRST02
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: larry.lai <larry.lai@yunjingtech.com>
> ---
> RFC 2023/04/25 -> PATCH V4
> (1) Fixed kernel test robot compiler warning.
> (2) Remove mistakes with wrong Reviewed-by tags.
> RFC 2022/11/23 -> RFC 2023/04/25
> (1) Refer 2022/12/08 Andy Shevchenko review, cleaned up coding style
> and addressed review comments.
> PATCH V3 -> RFC 2022/11/23:
> (1) Refer 2022/11/16 Lee Jones review, cleaned up coding style and
> addressed review comments.
> (2) Description on the UP Boards FPGA register read/write protocols
> PATCH V2 -> V3:
> (1) fixed kernel test robot compiler warning.
> PATCH V1 -> V2:
> (1) Synchronizing upboard github to rc2
> (2) Refer 2022/10/31 Lee Jones review, fixed some of the issues.
> ---
>  drivers/mfd/Kconfig              |  12 +
>  drivers/mfd/Makefile             |   1 +
>  drivers/mfd/upboard-fpga.c       | 526 +++++++++++++++++++++++++++++++
>  include/linux/mfd/upboard-fpga.h |  61 ++++
>  4 files changed, 600 insertions(+)
>  create mode 100644 drivers/mfd/upboard-fpga.c
>  create mode 100644 include/linux/mfd/upboard-fpga.h
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index abb58ab1a1a4..1041e937fc7a 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -2104,6 +2104,18 @@ config MFD_QCOM_PM8008
>  	  under it in the device tree. Additional drivers must be enabled in
>  	  order to use the functionality of the device.
>  
> +config MFD_INTEL_UPBOARD_FPGA
> +	tristate "Support for the Intel platform foundation kit UP board FPGA"
> +	select MFD_CORE
> +	depends on X86 && ACPI
> +	help
> +	  Select this option to enable the Intel AAEON UP and UP^2 on-board FPGA.
> +	  This is core driver for the UP board that implements certain (pin
> +	  control, onboard LEDs or CEC) through an on-board FPGA.
> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called upboard-fpga.
> +
>  menu "Multimedia Capabilities Port drivers"
>  	depends on ARCH_SA1100
>  
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 858cacf659d6..8374a05f6f43 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -250,6 +250,7 @@ obj-$(CONFIG_MFD_ALTERA_A10SR)	+= altera-a10sr.o
>  obj-$(CONFIG_MFD_ALTERA_SYSMGR) += altera-sysmgr.o
>  obj-$(CONFIG_MFD_STPMIC1)	+= stpmic1.o
>  obj-$(CONFIG_MFD_SUN4I_GPADC)	+= sun4i-gpadc.o
> +obj-$(CONFIG_MFD_INTEL_UPBOARD_FPGA)	+= upboard-fpga.o
>  
>  obj-$(CONFIG_MFD_STM32_LPTIMER)	+= stm32-lptimer.o
>  obj-$(CONFIG_MFD_STM32_TIMERS) 	+= stm32-timers.o
> diff --git a/drivers/mfd/upboard-fpga.c b/drivers/mfd/upboard-fpga.c
> new file mode 100644
> index 000000000000..a9a231e6d431
> --- /dev/null
> +++ b/drivers/mfd/upboard-fpga.c
> @@ -0,0 +1,526 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * UP Board multi function device driver for control CPLD/FPGA to

Remove all references to MFD.

> + * provide more GPIO driving power also provide CPLD LEDs and pin mux function
> + * recognize HID AANT0F00 ~ AAANT0F04 in ACPI name space
> + *
> + * Copyright (c) AAEON. All rights reserved.

Would you like to date it?

> + *
> + * Author: Gary Wang <garywang@aaeon.com.tw>

Who is Gary Wang and why are they not mentioned in the sign-off-block?

> + *

Remove this line.
> + */

New line here.

> +#include <linux/acpi.h>
> +#include <linux/dmi.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/kernel.h>
> +#include <linux/leds.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mfd/upboard-fpga.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/bits.h>
> +#include <linux/err.h>

Alphabetical.

Are you sure *all* of these are used?

> +struct upboard_fpga_data {
> +	const struct regmap_config *cpld_config;

Call this 'regmap_config'.

> +	const struct mfd_cell *cells;
> +	size_t ncells;
> +};
> +
> +#define AAEON_MANUFACTURER_ID		0x01
> +#define SUPPORTED_FW_MAJOR		0x0
> +#define MENUFACTURER_ID_MASK		GENMASK(7, 0)
> +
> +#define FIRMWARE_ID_BUILD_OFFSET	(12)
> +#define FIRMWARE_ID_MAJOR_OFFSET	(8)
> +#define FIRMWARE_ID_MINOR_OFFSET	(4)
> +#define FIRMWARE_ID_PATCH_OFFSET	(0)

Over parenthesised.

> +#define FIRMWARE_ID_MASK		GENMASK(3, 0)
> +
> +/*
> + * For UP Board Series FPGA register read/write protocols
> + * EMUTEX specs:
> + * D0   D1  D2  D3  D4  D5  D6  D7  D8  D9 .... D22  D23
> + * [RW][        address           ][        DATA        ]
> + *
> + * Read Sequence:
> + *      ___   ____________________________________________________   _________
> + * clr:    \_/ <--low-pulse does start the write-readback         \_/<--start
> + *              sequence with partital reset of internal          new sequence
> + *              registers but the CONF-REG.
> + *        ____________________________________________________________________
> + * rst: _/       _   _   _        _   _   _   __       __   __   _
> + * stb: STB#1->_/1\_/2\_/3\_...._/7\_/8\_/9\_/10\_..../23\_/24\_/<-STB#25 edge
> + *                                                                   is needed
> + *                                                                   to ACK
> + *             (D0 - D7 stb rising latch)
> + * data_in:     D0  D1  D2  .... D6  D7  don't ........ care(DC)
> + * data_out:    don't ...........care(DC)  D8   D9 ....  D22  D23
> + *                                   (D8 - D23 stb falling latch)
> + * flag_Read:                             _________...._________
> + *      __DC_   ____________...._________/                      \_
> + * counter:
> + *    [00]DC[00][01][02] ............[08][9][10]............[24][00]
> + * CONF-REG:
> + *    [00] [                     CONF-REG                       ]
> + * wreg:
> + *    [00]DC[00][  wreg=SHFT(wreg)  ][ADR][DATA][wreg=SHFT(wreg)]
> + * wreg2:
> + *                                        [    (COPY)=ADDR      ]
> + */

Not sure you need all of this here.  If you want to share the protocol,
I suggest a separate doc in /Documentation, maybe /Documentation/fpga.

> +static int upboard_fpga_read(void *context, unsigned int reg, unsigned int *val)
> +{
> +	struct upboard_fpga * const fpga = context;
> +	int i;
> +
> +	gpiod_set_value(fpga->clear_gpio, 0);
> +	gpiod_set_value(fpga->clear_gpio, 1);

Instead of the huge protocol description in the function header, it
would be nicer to place one liners above these sections instead.

  /* Place device into X state */

  /* Transfer data section */

Etc.

> +
> +	reg |= UPFPGA_READ_FLAG;
> +
> +	for (i = UPFPGA_ADDRESS_SIZE; i >= 0; i--) {
> +		gpiod_set_value(fpga->strobe_gpio, 0);
> +		gpiod_set_value(fpga->datain_gpio, !!(reg & BIT(i)));
> +		gpiod_set_value(fpga->strobe_gpio, 1);
> +	}
> +
> +	gpiod_set_value(fpga->strobe_gpio, 0);
> +	*val = 0;
> +
> +	for (i = UPFPGA_REGISTER_SIZE - 1; i >= 0; i--) {
> +		gpiod_set_value(fpga->strobe_gpio, 1);
> +		gpiod_set_value(fpga->strobe_gpio, 0);
> +		*val |= gpiod_get_value(fpga->dataout_gpio) << i;
> +	}
> +
> +	gpiod_set_value(fpga->strobe_gpio, 1);
> +
> +	return 0;
> +}
> +
> +/*
> + * Write Sequence:
> + *      ___   ____________________________________________________   _________
> + * clr:    \_/ <--low-pulse does start the write-readback         \_/<--start
> + *              sequence with partital reset of internal          new sequence
> + *              registers but the CONF-REG.
> + *        ____________________________________________________________________
> + * rst: _/       _   _   _        _   _   _   __       __   __   _
> + * stb: STB#1->_/1\_/2\_/3\_...._/7\_/8\_/9\_/10\_..../23\_/24\_/<-STB#25 edge
> + *                                                                   is needed
> + *                                                                   to ACK
> + *             (D0 - D23 stb rising latch)
> + * data_in:     D0  D1  D2  .... D6  D7  D8  D9 ....  D22  D23
> + * data_out:    don't ................................care (DC)
> + * flag_Read:
> + *      __DC_   ____________....__________________________________
> + * counter:
> + *    [00]DC[00][01][02] ............[08][9][10]............[24][00]
> + * wreg:
> + *    [00]DC[00][wreg=SHFT(wreg)&dat_in ][SHFT(wreg)&dat_in][DAT]
> + * wreg2:
> + *                                   [     (COPY)=ADDR          ]
> + * CONF-REG:
> + *    [00] [                 CONF-REG = OLD VALUE               ][CONF-REG=DAT]
> + */
> +static int upboard_fpga_write(void *context, unsigned int reg, unsigned int val)
> +{
> +	struct upboard_fpga * const fpga = context;
> +	int i;
> +
> +	gpiod_set_value(fpga->clear_gpio, 0);
> +	gpiod_set_value(fpga->clear_gpio, 1);
> +
> +	for (i = UPFPGA_ADDRESS_SIZE; i >= 0; i--) {
> +		gpiod_set_value(fpga->strobe_gpio, 0);
> +		gpiod_set_value(fpga->datain_gpio, !!(reg & BIT(i)));
> +		gpiod_set_value(fpga->strobe_gpio, 1);
> +	}
> +
> +	gpiod_set_value(fpga->strobe_gpio, 0);
> +
> +	for (i = UPFPGA_REGISTER_SIZE - 1; i >= 0; i--) {
> +		gpiod_set_value(fpga->datain_gpio, !!(val & BIT(i)));
> +		gpiod_set_value(fpga->strobe_gpio, 1);
> +		gpiod_set_value(fpga->strobe_gpio, 0);
> +	}
> +
> +	gpiod_set_value(fpga->strobe_gpio, 1);
> +
> +	return 0;
> +}
> +
> +static const struct regmap_range upboard_up_readable_ranges[] = {
> +	regmap_reg_range(UPFPGA_REG_PLATFORM_ID, UPFPGA_REG_FIRMWARE_ID),
> +	regmap_reg_range(UPFPGA_REG_FUNC_EN0, UPFPGA_REG_FUNC_EN0),
> +	regmap_reg_range(UPFPGA_REG_GPIO_DIR0, UPFPGA_REG_GPIO_DIR1),
> +};
> +
> +static const struct regmap_range upboard_up_writable_ranges[] = {
> +	regmap_reg_range(UPFPGA_REG_FUNC_EN0, UPFPGA_REG_FUNC_EN0),
> +	regmap_reg_range(UPFPGA_REG_GPIO_DIR0, UPFPGA_REG_GPIO_DIR1),
> +};
> +
> +static const struct regmap_access_table upboard_up_readable_table = {
> +	.yes_ranges = upboard_up_readable_ranges,
> +	.n_yes_ranges = ARRAY_SIZE(upboard_up_readable_ranges),
> +};
> +
> +static const struct regmap_access_table upboard_up_writable_table = {
> +	.yes_ranges = upboard_up_writable_ranges,
> +	.n_yes_ranges = ARRAY_SIZE(upboard_up_writable_ranges),
> +};
> +
> +static const struct regmap_config upboard_up_regmap_config = {
> +	.reg_bits = UPFPGA_ADDRESS_SIZE,
> +	.val_bits = UPFPGA_REGISTER_SIZE,
> +	.max_register = UPFPGA_REG_MAX,
> +	.reg_read = upboard_fpga_read,
> +	.reg_write = upboard_fpga_write,
> +	.fast_io = false,
> +	.cache_type = REGCACHE_RBTREE,
> +	.rd_table = &upboard_up_readable_table,
> +	.wr_table = &upboard_up_writable_table,
> +};
> +
> +static struct upboard_led_data upboard_up_led_data[] = {
> +	{ .bit = 0, .colour = "yellow" },
> +	{ .bit = 1, .colour = "green" },
> +	{ .bit = 2, .colour = "red" },
> +};

Encode this information into the LED driver.



> +static const struct mfd_cell upboard_up_mfd_cells[] = {
> +	{ .name = "upboard-pinctrl" },
> +	MFD_CELL_BASIC("upboard-led", NULL, &upboard_up_led_data[0],
> +		       sizeof(*upboard_up_led_data), 0),
> +	MFD_CELL_BASIC("upboard-led", NULL, &upboard_up_led_data[1],
> +		       sizeof(*upboard_up_led_data), 1),
> +	MFD_CELL_BASIC("upboard-led", NULL, &upboard_up_led_data[2],
> +		       sizeof(*upboard_up_led_data), 2),
> +};
> +
> +/* UP Squared 6000 EHL board */
> +
> +static const struct upboard_fpga_data upboard_up_fpga_data = {
> +	.cpld_config = &upboard_up_regmap_config,
> +	.cells = upboard_up_mfd_cells,
> +	.ncells = ARRAY_SIZE(upboard_up_mfd_cells),
> +};
> +
> +static const struct mfd_cell upboard_pinctrl_cells[] = {
> +	{ .name = "upboard-pinctrl" },
> +};
> +
> +static const struct upboard_fpga_data upboard_pinctrl_data = {
> +	.cpld_config = &upboard_up_regmap_config,
> +	.cells = upboard_pinctrl_cells,
> +	.ncells = ARRAY_SIZE(upboard_pinctrl_cells),
> +};
> +
> +/* UP^2 board */
> +static const struct regmap_range upboard_up2_readable_ranges[] = {
> +	regmap_reg_range(UPFPGA_REG_PLATFORM_ID, UPFPGA_REG_FIRMWARE_ID),
> +	regmap_reg_range(UPFPGA_REG_FUNC_EN0, UPFPGA_REG_FUNC_EN1),
> +	regmap_reg_range(UPFPGA_REG_GPIO_EN0, UPFPGA_REG_GPIO_EN2),
> +	regmap_reg_range(UPFPGA_REG_GPIO_DIR0, UPFPGA_REG_GPIO_DIR2),
> +};
> +
> +static const struct regmap_range upboard_up2_writable_ranges[] = {
> +	regmap_reg_range(UPFPGA_REG_FUNC_EN0, UPFPGA_REG_FUNC_EN1),
> +	regmap_reg_range(UPFPGA_REG_GPIO_EN0, UPFPGA_REG_GPIO_EN2),
> +	regmap_reg_range(UPFPGA_REG_GPIO_DIR0, UPFPGA_REG_GPIO_DIR2),
> +};
> +
> +static const struct regmap_access_table upboard_up2_readable_table = {
> +	.yes_ranges = upboard_up2_readable_ranges,
> +	.n_yes_ranges = ARRAY_SIZE(upboard_up2_readable_ranges),
> +};
> +
> +static const struct regmap_access_table upboard_up2_writable_table = {
> +	.yes_ranges = upboard_up2_writable_ranges,
> +	.n_yes_ranges = ARRAY_SIZE(upboard_up2_writable_ranges),
> +};
> +
> +static const struct regmap_config upboard_up2_regmap_config = {
> +	.reg_bits = UPFPGA_ADDRESS_SIZE,
> +	.val_bits = UPFPGA_REGISTER_SIZE,
> +	.max_register = UPFPGA_REG_MAX,
> +	.reg_read = upboard_fpga_read,
> +	.reg_write = upboard_fpga_write,
> +	.fast_io = false,
> +	.cache_type = REGCACHE_NONE,
> +	.rd_table = &upboard_up2_readable_table,
> +	.wr_table = &upboard_up2_writable_table,
> +};
> +
> +static struct upboard_led_data upboard_up2_led_data[] = {
> +	{ .bit = 0, .colour = "blue" },
> +	{ .bit = 1, .colour = "yellow" },
> +	{ .bit = 2, .colour = "green" },
> +	{ .bit = 3, .colour = "red" },
> +};
> +
> +static const struct mfd_cell upboard_up2_mfd_cells[] = {
> +	{ .name = "upboard-pinctrl" },

MFD_CELL_NAME()

> +	MFD_CELL_BASIC("upboard-led", NULL, &upboard_up2_led_data[0],
> +		       sizeof(*upboard_up2_led_data), 0),

What are you using the id for here?  

Does PLATFORM_DEVID_AUTO not already do the right thing?

> +	MFD_CELL_BASIC("upboard-led", NULL, &upboard_up2_led_data[1],
> +		       sizeof(*upboard_up2_led_data), 1),
> +	MFD_CELL_BASIC("upboard-led", NULL, &upboard_up2_led_data[2],
> +		       sizeof(*upboard_up2_led_data), 2),
> +	MFD_CELL_BASIC("upboard-led", NULL, &upboard_up2_led_data[3],
> +		       sizeof(*upboard_up2_led_data), 3),
> +};
> +
> +static const struct upboard_fpga_data upboard_up2_fpga_data = {
> +	.cpld_config = &upboard_up2_regmap_config,
> +	.cells = upboard_up2_mfd_cells,
> +	.ncells = ARRAY_SIZE(upboard_up2_mfd_cells),
> +};
> +
> +/* UP-CRST02 carrier board for UP Core */
> +
> +/* same MAX10 config as UP2, but same LED cells as UP1 */
> +static const struct upboard_fpga_data upboard_upcore_crst02_fpga_data = {
> +	.cpld_config = &upboard_up2_regmap_config,
> +	.cells = upboard_up_mfd_cells,
> +	.ncells = ARRAY_SIZE(upboard_up_mfd_cells),
> +};
> +
> +static int __init upboard_fpga_gpio_init(struct upboard_fpga *fpga)
> +{
> +	enum gpiod_flags flags = fpga->uninitialised ? GPIOD_OUT_LOW : GPIOD_ASIS;
> +
> +	fpga->enable_gpio = devm_gpiod_get(fpga->dev, "enable", flags);
> +	if (IS_ERR(fpga->enable_gpio))
> +		return PTR_ERR(fpga->enable_gpio);
> +
> +	fpga->clear_gpio = devm_gpiod_get(fpga->dev, "clear", GPIOD_OUT_LOW);
> +	if (IS_ERR(fpga->clear_gpio))
> +		return PTR_ERR(fpga->clear_gpio);
> +
> +	fpga->strobe_gpio = devm_gpiod_get(fpga->dev, "strobe", GPIOD_OUT_LOW);
> +	if (IS_ERR(fpga->strobe_gpio))
> +		return PTR_ERR(fpga->strobe_gpio);
> +
> +	fpga->datain_gpio = devm_gpiod_get(fpga->dev, "datain", GPIOD_OUT_LOW);
> +	if (IS_ERR(fpga->datain_gpio))
> +		return PTR_ERR(fpga->datain_gpio);
> +
> +	fpga->dataout_gpio = devm_gpiod_get(fpga->dev, "dataout", GPIOD_IN);
> +	if (IS_ERR(fpga->dataout_gpio))
> +		return PTR_ERR(fpga->dataout_gpio);
> +
> +	/*
> +	 * The SoC pinctrl driver may not support reserving the GPIO line for
> +	 * FPGA reset without causing an undesired reset pulse. This will clear
> +	 * any settings on the FPGA, so only do it if we must.
> +	 * Reset GPIO defaults HIGH, get GPIO and set to LOW, then set back to
> +	 * HIGH as a pulse.
> +	 */
> +	if (fpga->uninitialised) {
> +		fpga->reset_gpio = devm_gpiod_get(fpga->dev, "reset", GPIOD_OUT_LOW);
> +		if (IS_ERR(fpga->reset_gpio))
> +			return PTR_ERR(fpga->reset_gpio);
> +
> +		gpiod_set_value(fpga->reset_gpio, 1);

Better to define these.

#define RESET_DEVICE 1

> +	}
> +
> +	gpiod_set_value(fpga->enable_gpio, 1);

#define ENABLE_DEVICE 1

> +	fpga->uninitialised = false;

Why would this be called on a device that has already been initialised?

> +	return 0;
> +}
> +
> +/*
> + * This function is for debugging with user for showing firmware information.
> + */

Remove this comment.

> +static int __init upboard_fpga_show_firmware_info(struct upboard_fpga *fpga)

upboard_fpga_verify_device()

> +{
> +	unsigned int platform_id, manufacturer_id;
> +	unsigned int firmware_id, build, major, minor, patch;
> +	int ret;
> +
> +	if (!fpga)
> +		return -ENOMEM;

I don't believe this is possible.

> +	ret = regmap_read(fpga->regmap, UPFPGA_REG_PLATFORM_ID, &platform_id);
> +	if (ret)
> +		return ret;
> +
> +	manufacturer_id = platform_id & MENUFACTURER_ID_MASK;
> +	if (manufacturer_id != AAEON_MANUFACTURER_ID) {
> +		dev_err(fpga->dev,
> +			"driver not compatible with custom FPGA FW from manufacturer id 0x%02x. Exiting",

"Manufacturer ID 0x%02x not supported\n"

> +			manufacturer_id);
> +
> +		return -ENODEV;
> +	}
> +
> +	ret = regmap_read(fpga->regmap, UPFPGA_REG_FIRMWARE_ID, &firmware_id);
> +	if (ret)
> +		return ret;
> +
> +	build = (firmware_id >> FIRMWARE_ID_BUILD_OFFSET) & FIRMWARE_ID_MASK;
> +	major = (firmware_id >> FIRMWARE_ID_MAJOR_OFFSET) & FIRMWARE_ID_MASK;
> +	minor = (firmware_id >> FIRMWARE_ID_MINOR_OFFSET) & FIRMWARE_ID_MASK;
> +	patch = (firmware_id >> FIRMWARE_ID_PATCH_OFFSET) & FIRMWARE_ID_MASK;
> +
> +	if (major != SUPPORTED_FW_MAJOR) {
> +		dev_err(fpga->dev, "unsupported FPGA FW v%u.%u.%u build 0x%02x",

As above.

> +			major, minor, patch, build);
> +
> +		return -ENODEV;
> +	}
> +
> +	dev_info(fpga->dev, "compatible FPGA FW v%u.%u.%u build 0x%02x",

"Compatible ..."

> +		 major, minor, patch, build);
> +
> +	return 0;
> +}
> +
> +/*
> + * MFD upboard-fpga is ACPI driver and can recognize the AANT ID from different
> + * kind of upboards. We get the LED GPIO initialized information from this
> + * then add led-upboard driver.
> + */

Remove this comment.

> +int upboard_led_gpio_register(struct upboard_fpga *fpga)
> +{
> +	struct gpio_led blue_led, yellow_led, green_led, red_led;
> +	struct gpio_desc *desc;
> +	static struct gpio_led upboard_gpio_leds[4];

Just 'leds'

> +	int leds = 0;

'num_leds' or 'leds_count'.

> +	static struct gpio_led_platform_data upboard_gpio_led_platform_data;

Just 'pdata' is fine.

Move this line to the top.

> +	static const struct mfd_cell upboard_gpio_led_cells[] = {
> +		MFD_CELL_BASIC("leds-gpio", NULL,
> +			       &upboard_gpio_led_platform_data,
> +			       sizeof(upboard_gpio_led_platform_data), 0)
> +	};

Please define this statically, outside of the function.

> +	int ret;
> +
> +	desc = devm_gpiod_get(fpga->dev, "blue", GPIOD_OUT_LOW);
> +	if (!IS_ERR(desc)) {
> +		blue_led.name = "upboard:blue:";
> +		blue_led.gpio = desc_to_gpio(desc);
> +		blue_led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
> +		upboard_gpio_leds[leds++] = blue_led;
> +		devm_gpiod_put(fpga->dev, desc);
> +	}

'\n' between each.

> +	desc = devm_gpiod_get(fpga->dev, "yellow", GPIOD_OUT_LOW);
> +	if (!IS_ERR(desc)) {
> +		yellow_led.name = "upboard:yellow:";
> +		yellow_led.gpio = desc_to_gpio(desc);
> +		yellow_led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
> +		upboard_gpio_leds[leds++] = yellow_led;
> +		devm_gpiod_put(fpga->dev, desc);
> +	}
> +	desc = devm_gpiod_get(fpga->dev, "green", GPIOD_OUT_LOW);
> +	if (!IS_ERR(desc)) {
> +		green_led.name = "upboard:green:";
> +		green_led.gpio = desc_to_gpio(desc);
> +		green_led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
> +		upboard_gpio_leds[leds++] = green_led;
> +		devm_gpiod_put(fpga->dev, desc);
> +	}
> +	desc = devm_gpiod_get(fpga->dev, "red", GPIOD_OUT_LOW);
> +	if (!IS_ERR(desc)) {
> +		red_led.name = "upboard:red:";
> +		red_led.gpio = desc_to_gpio(desc);
> +		red_led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
> +		upboard_gpio_leds[leds++] = red_led;
> +		devm_gpiod_put(fpga->dev, desc);
> +	}
> +
> +	/* no LEDs */

No optional LEDs defined.

> +	if (leds == 0)
> +		return 0;
> +
> +	upboard_gpio_led_platform_data.num_leds = leds;
> +	upboard_gpio_led_platform_data.leds = upboard_gpio_leds;
> +
> +	ret = devm_mfd_add_devices(fpga->dev, PLATFORM_DEVID_AUTO,
> +				   upboard_gpio_led_cells,
> +				   ARRAY_SIZE(upboard_gpio_led_cells),
> +				   NULL, 0, NULL);
> +	if (ret) {
> +		dev_err(fpga->dev, "Failed to add GPIO LEDs,%d", ret);

Space after the ','.

> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct acpi_device_id upboard_fpga_acpi_match[] = {
> +	{ "AANT0000", (kernel_ulong_t)&upboard_pinctrl_data },
> +	{ "AANT0F00", (kernel_ulong_t)&upboard_up_fpga_data },
> +	{ "AANT0F01", (kernel_ulong_t)&upboard_up2_fpga_data },
> +	{ "AANT0F02", (kernel_ulong_t)&upboard_up_fpga_data },
> +	{ "AANT0F03", (kernel_ulong_t)&upboard_upcore_crst02_fpga_data },
> +	{ "AANT0F04", (kernel_ulong_t)&upboard_up_fpga_data },

Please don't pass MFD data through other platform APIs.

Pass a device ID and match on that instead.

> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, upboard_fpga_acpi_match);
> +
> +static int __init upboard_fpga_probe(struct platform_device *pdev)
> +{
> +	struct upboard_fpga *fpga;

Call this 'ddata'.

> +	const struct acpi_device_id *id;
> +	const struct upboard_fpga_data *fpga_data;

You should be able to delete this structure entirely if you match on ID.

> +	int ret;
> +	struct device *dev = &pdev->dev;

Place this on the top.

> +	id = acpi_match_device(upboard_fpga_acpi_match, dev);
> +	if (!id)
> +		return -ENODEV;
> +
> +	fpga_data = (const struct upboard_fpga_data *) id->driver_data;
> +
> +	fpga = devm_kzalloc(dev, sizeof(*fpga), GFP_KERNEL);
> +	if (!fpga)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, fpga);
> +	fpga->regmap = devm_regmap_init(dev, NULL, fpga, fpga_data->cpld_config);
> +	fpga->cpld_config = (struct regmap_config *)fpga_data->cpld_config;

Why would this need to be cast?

> +	if (IS_ERR(fpga->regmap))
> +		return PTR_ERR(fpga->regmap);

This needs to go directly after the call to devm_regmap_init().

> +	ret = upboard_fpga_gpio_init(fpga);
> +	if (ret) {
> +		/*
> +		 * This is for compatiable with some upboards w/o FPGA firmware,
> +		 * so just showing debug info and do not return directly.
> +		 */

Sorry, I don't understand.  What use-case is this catching?

> +		dev_warn(dev, "Failed to initialize FPGA common GPIOs: %d", ret);
> +	} else {
> +		upboard_fpga_show_firmware_info(fpga);
> +	}
> +
> +	/* register GPIO LEDs */

The function name is descriptive enough.

> +	ret = upboard_led_gpio_register(fpga);
> +	if (ret) {
> +		/*
> +		 * This is for compatiable with some upboards w/o LEDs.
> +		 */

/* LEDs are optional */

> +		dev_warn(dev, "Failed to register LEDs: %d", ret);
> +	}
> +
> +	return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
> +				    fpga_data->cells,
> +				    fpga_data->ncells,
> +				    NULL, 0, NULL);
> +}
> +
> +static struct platform_driver upboard_fpga_driver = {
> +	.driver = {
> +		.name = "upboard-fpga",
> +		.acpi_match_table = upboard_fpga_acpi_match,
> +	},
> +};
> +module_platform_driver_probe(upboard_fpga_driver, upboard_fpga_probe);
> +
> +MODULE_AUTHOR("Gary Wang <garywang@aaeon.com.tw>");
> +MODULE_DESCRIPTION("UP Board CPLD/FPGA driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/mfd/upboard-fpga.h b/include/linux/mfd/upboard-fpga.h
> new file mode 100644
> index 000000000000..1fa073e5c53c
> --- /dev/null
> +++ b/include/linux/mfd/upboard-fpga.h
> @@ -0,0 +1,61 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * UP Board CPLD/FPGA driver
> + *
> + * Copyright (c) AAEON. All rights reserved.
> + *
> + * Author: Gary Wang <garywang@aaeon.com.tw>
> + *
> + */
> +
> +#ifndef __LINUX_MFD_UPBOARD_FPGA_H
> +#define __LINUX_MFD_UPBOARD_FPGA_H

Remove the "LINUX_" part.

> +#include <linux/device.h>
> +#include <linux/regmap.h>

GPIO?

> +/* CPLD/FPGA protocol version */
> +#define UPFPGA_PROTOCOL_V1_HRV		1
> +#define UPFPGA_PROTOCOL_V2_HRV		2
> +
> +#define UPFPGA_ADDRESS_SIZE		7
> +#define UPFPGA_REGISTER_SIZE		16
> +
> +#define UPFPGA_READ_FLAG		(1 << UPFPGA_ADDRESS_SIZE)

BIT()?

> +enum upboard_fpgareg {
> +	UPFPGA_REG_PLATFORM_ID		= 0x10,
> +	UPFPGA_REG_FIRMWARE_ID		= 0x11,
> +	UPFPGA_REG_FUNC_EN0		= 0x20,
> +	UPFPGA_REG_FUNC_EN1		= 0x21,
> +	UPFPGA_REG_GPIO_EN0		= 0x30,
> +	UPFPGA_REG_GPIO_EN1		= 0x31,
> +	UPFPGA_REG_GPIO_EN2		= 0x32,
> +	UPFPGA_REG_GPIO_DIR0		= 0x40,
> +	UPFPGA_REG_GPIO_DIR1		= 0x41,
> +	UPFPGA_REG_GPIO_DIR2		= 0x42,
> +	UPFPGA_REG_MAX,
> +};
> +
> +struct upboard_fpga {
> +	struct device			*dev;
> +	struct regmap			*regmap;
> +	struct regmap_config		*cpld_config;
> +	struct gpio_desc		*enable_gpio;
> +	struct gpio_desc		*reset_gpio;
> +	struct gpio_desc		*clear_gpio;
> +	struct gpio_desc		*strobe_gpio;
> +	struct gpio_desc		*datain_gpio;
> +	struct gpio_desc		*dataout_gpio;
> +	bool				uninitialised;
> +};
> +
> +struct upboard_led_data {
> +	unsigned int			bit;
> +	const char			*colour;
> +};
> +
> +bool regmap_check_writeable(struct upboard_fpga *fpga, unsigned int reg);
> +int upboard_led_gpio_register(struct upboard_fpga *fpga);

Why are these here?

> +#endif /*  __LINUX_MFD_UPBOARD_FPGA_H */
> -- 
> 2.17.1
>