Date:   Fri, 17 Feb 2023 21:00:31 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     William Breathitt Gray <william.gray@...aro.org>
Cc:     linus.walleij@...aro.org, brgl@...ev.pl, broonie@...nel.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] gpio: idio-16: Migrate to the regmap API

On Wed, Feb 08, 2023 at 12:18:18PM -0500, William Breathitt Gray wrote:
> The regmap API supports IO port accessors so we can take advantage of
> regmap abstractions rather than handling access to the device registers
> directly in the driver.
> 
> By leveraging the regmap API, the idio-16 library is reduced to simply a
> devm_idio_16_regmap_register() function and a configuration structure
> struct idio_16_regmap_config.
> 
> Legacy functions and code will be removed once all consumers have
> migrated to the new idio-16 library interface.
> 
> For IDIO-16 devices we have the following IRQ registers:
> 
>     Base Address +1 (Write): Clear Interrupt
>     Base Address +2 (Read): Enable Interrupt
>     Base Address +2 (Write): Disable Interrupt
> 
> An interrupt is asserted whenever a change-of-state is detected on any
> of the inputs. Any write to 0x2 will disable interrupts, while any read
> will enable interrupts. Interrupts are cleared by a write to 0x1.
> 
> For 104-IDIO-16 devices, there is no IRQ status register, so software
> has to assume that if an interrupt is raised then it was for the
> 104-IDIO-16 device.
> 
> For PCI-IDIO-16 devices, there is an additional IRQ register:
> 
>     Base Address +6 (Read): Interrupt Status
> 
> Interrupt status can be read from 0x6 where bit 2 set indicates that an
> IRQ has been generated.

LGTM,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

One minor remark below.

> Signed-off-by: William Breathitt Gray <william.gray@...aro.org>
> ---
>  drivers/gpio/Kconfig        |   3 +
>  drivers/gpio/gpio-idio-16.c | 158 ++++++++++++++++++++++++++++++++++++
>  drivers/gpio/gpio-idio-16.h |  28 +++++++
>  3 files changed, 189 insertions(+)
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 406e8bda487f..b4de83a3616d 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -111,6 +111,9 @@ config GPIO_MAX730X
>  
>  config GPIO_IDIO_16
>  	tristate
> +	select REGMAP_IRQ
> +	select GPIOLIB_IRQCHIP
> +	select GPIO_REGMAP
>  	help
>  	  Enables support for the idio-16 library functions. The idio-16 library
>  	  provides functions to facilitate communication with devices within the
> diff --git a/drivers/gpio/gpio-idio-16.c b/drivers/gpio/gpio-idio-16.c
> index 13315242d220..907b0f15fdb3 100644
> --- a/drivers/gpio/gpio-idio-16.c
> +++ b/drivers/gpio/gpio-idio-16.c
> @@ -4,9 +4,13 @@
>   * Copyright (C) 2022 William Breathitt Gray
>   */
>  #include <linux/bitmap.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
>  #include <linux/export.h>
> +#include <linux/gpio/regmap.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> +#include <linux/regmap.h>
>  #include <linux/spinlock.h>
>  #include <linux/types.h>
>  
> @@ -14,6 +18,160 @@
>  
>  #define DEFAULT_SYMBOL_NAMESPACE GPIO_IDIO_16
>  
> +#define IDIO_16_DAT_BASE 0x0
> +#define IDIO_16_OUT_BASE IDIO_16_DAT_BASE
> +#define IDIO_16_IN_BASE (IDIO_16_DAT_BASE + 1)
> +#define IDIO_16_CLEAR_INTERRUPT 0x1
> +#define IDIO_16_ENABLE_IRQ 0x2
> +#define IDIO_16_DEACTIVATE_INPUT_FILTERS 0x3
> +#define IDIO_16_DISABLE_IRQ IDIO_16_ENABLE_IRQ
> +#define IDIO_16_INTERRUPT_STATUS 0x6
> +
> +#define IDIO_16_NGPIO 32
> +#define IDIO_16_NGPIO_PER_REG 8
> +#define IDIO_16_REG_STRIDE 4
> +
> +static int idio_16_handle_mask_sync(struct regmap *const map, const int index,
> +				   const unsigned int mask_buf_def,
> +				   const unsigned int mask_buf,
> +				   void *const irq_drv_data)
> +{
> +	unsigned int *const irq_mask = irq_drv_data;
> +	const unsigned int prev_mask = *irq_mask;
> +	int err;
> +	unsigned int val;
> +
> +	/* exit early if no change since the previous mask */
> +	if (mask_buf == prev_mask)
> +		return 0;
> +
> +	/* remember the current mask for the next mask sync */
> +	*irq_mask = mask_buf;
> +
> +	/* if all previously masked, enable interrupts when unmasking */
> +	if (prev_mask == mask_buf_def) {
> +		err = regmap_write(map, IDIO_16_CLEAR_INTERRUPT, 0x00);
> +		if (err)
> +			return err;
> +		return regmap_read(map, IDIO_16_ENABLE_IRQ, &val);
> +	}
> +
> +	/* if all are currently masked, disable interrupts */
> +	if (mask_buf == mask_buf_def)
> +		return regmap_write(map, IDIO_16_DISABLE_IRQ, 0x00);
> +
> +	return 0;
> +}
> +
> +static int idio_16_reg_mask_xlate(struct gpio_regmap *gpio, unsigned int base,
> +				  unsigned int offset, unsigned int *reg,
> +				  unsigned int *mask)
> +{
> +	unsigned int stride;
> +
> +	if (base != IDIO_16_DAT_BASE) {
> +		/* Should never reach this path */
> +		return -EINVAL;
> +	}
> +
> +	/* Input lines start at GPIO 16 */
> +	if (offset < 16) {
> +		stride = offset / IDIO_16_NGPIO_PER_REG;
> +		*reg = IDIO_16_OUT_BASE + stride * IDIO_16_REG_STRIDE;
> +	} else {
> +		stride = (offset - 16) / IDIO_16_NGPIO_PER_REG;
> +		*reg = IDIO_16_IN_BASE + stride * IDIO_16_REG_STRIDE;
> +	}
> +
> +	*mask = BIT(offset % IDIO_16_NGPIO_PER_REG);
> +
> +	return 0;
> +}
> +
> +static const char *idio_16_names[IDIO_16_NGPIO] = {
> +	"OUT0", "OUT1", "OUT2", "OUT3", "OUT4", "OUT5", "OUT6", "OUT7",
> +	"OUT8", "OUT9", "OUT10", "OUT11", "OUT12", "OUT13", "OUT14", "OUT15",
> +	"IIN0", "IIN1", "IIN2", "IIN3", "IIN4", "IIN5", "IIN6", "IIN7",
> +	"IIN8", "IIN9", "IIN10", "IIN11", "IIN12", "IIN13", "IIN14", "IIN15"

I would leave comma at the end.

> +};
> +
> +/**
> + * devm_idio_16_regmap_register - Register an IDIO-16 GPIO device
> + * @dev:	device that is registering this IDIO-16 GPIO device
> + * @config:	configuration for idio_16_regmap_config
> + *
> + * Registers an IDIO-16 GPIO device. Returns 0 on success and negative error
> + * number on failure.
> + */
> +int devm_idio_16_regmap_register(struct device *const dev,
> +				 const struct idio_16_regmap_config *const config)
> +{
> +	struct gpio_regmap_config gpio_config = {};
> +	int err;
> +	struct regmap_irq_chip *chip;
> +	unsigned int irq_mask;
> +	struct regmap_irq_chip_data *chip_data;
> +
> +	if (!config->parent)
> +		return -EINVAL;
> +
> +	if (!config->map)
> +		return -EINVAL;
> +
> +	if (!config->regmap_irqs)
> +		return -EINVAL;
> +
> +	chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
> +	if (!chip)
> +		return -ENOMEM;
> +
> +	chip->irq_drv_data = devm_kzalloc(dev, sizeof(irq_mask), GFP_KERNEL);
> +	if (!chip->irq_drv_data)
> +		return -ENOMEM;
> +
> +	chip->name = dev_name(dev);
> +	chip->status_base = IDIO_16_INTERRUPT_STATUS;
> +	chip->mask_base = IDIO_16_ENABLE_IRQ;
> +	chip->ack_base = IDIO_16_CLEAR_INTERRUPT;
> +	chip->no_status = config->no_status;
> +	chip->num_regs = 1;
> +	chip->irqs = config->regmap_irqs;
> +	chip->num_irqs = config->num_regmap_irqs;
> +	chip->handle_mask_sync = idio_16_handle_mask_sync;
> +
> +	/* Disable IRQ to prevent spurious interrupts before we're ready */
> +	err = regmap_write(config->map, IDIO_16_DISABLE_IRQ, 0x00);
> +	if (err)
> +		return err;
> +
> +	err = devm_regmap_add_irq_chip(dev, config->map, config->irq, 0, 0,
> +				       chip, &chip_data);
> +	if (err)
> +		return dev_err_probe(dev, err, "IRQ registration failed\n");
> +
> +	if (config->filters) {
> +		/* Deactivate input filters */
> +		err = regmap_write(config->map,
> +				   IDIO_16_DEACTIVATE_INPUT_FILTERS, 0x00);
> +		if (err)
> +			return err;
> +	}
> +
> +	gpio_config.parent = config->parent;
> +	gpio_config.regmap = config->map;
> +	gpio_config.ngpio = IDIO_16_NGPIO;
> +	gpio_config.names = idio_16_names;
> +	gpio_config.reg_dat_base = GPIO_REGMAP_ADDR(IDIO_16_DAT_BASE);
> +	gpio_config.reg_set_base = GPIO_REGMAP_ADDR(IDIO_16_DAT_BASE);
> +	gpio_config.ngpio_per_reg = IDIO_16_NGPIO_PER_REG;
> +	gpio_config.reg_stride = IDIO_16_REG_STRIDE;
> +	gpio_config.irq_domain = regmap_irq_get_domain(chip_data);
> +	gpio_config.reg_mask_xlate = idio_16_reg_mask_xlate;
> +
> +	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
> +}
> +EXPORT_SYMBOL_GPL(devm_idio_16_regmap_register);
> +
>  /**
>   * idio_16_get - get signal value at signal offset
>   * @reg:	ACCES IDIO-16 device registers
> diff --git a/drivers/gpio/gpio-idio-16.h b/drivers/gpio/gpio-idio-16.h
> index 928f8251a2bd..22bb591b4ec0 100644
> --- a/drivers/gpio/gpio-idio-16.h
> +++ b/drivers/gpio/gpio-idio-16.h
> @@ -6,6 +6,30 @@
>  #include <linux/spinlock.h>
>  #include <linux/types.h>
>  
> +struct device;
> +struct regmap;
> +struct regmap_irq;
> +
> +/**
> + * struct idio_16_regmap_config - Configuration for the IDIO-16 register map
> + * @parent:		parent device
> + * @map:		regmap for the IDIO-16 device
> + * @regmap_irqs:	descriptors for individual IRQs
> + * @num_regmap_irqs:	number of IRQ descriptors
> + * @irq:		IRQ number for the IDIO-16 device
> + * @no_status:		device has no status register
> + * @filters:		device has input filters
> + */
> +struct idio_16_regmap_config {
> +	struct device *parent;
> +	struct regmap *map;
> +	const struct regmap_irq *regmap_irqs;
> +	int num_regmap_irqs;
> +	unsigned int irq;
> +	bool no_status;
> +	bool filters;
> +};
> +
>  /**
>   * struct idio_16 - IDIO-16 registers structure
>   * @out0_7:	Read: FET Drive Outputs 0-7
> @@ -39,6 +63,7 @@ struct idio_16 {
>   * struct idio_16_state - IDIO-16 state structure
>   * @lock:	synchronization lock for accessing device state
>   * @out_state:	output signals state
> + * @irq_mask:	IRQ mask state
>   */
>  struct idio_16_state {
>  	spinlock_t lock;
> @@ -68,4 +93,7 @@ void idio_16_set_multiple(struct idio_16 __iomem *reg,
>  			  const unsigned long *mask, const unsigned long *bits);
>  void idio_16_state_init(struct idio_16_state *state);
>  
> +int devm_idio_16_regmap_register(struct device *dev,
> +				 const struct idio_16_regmap_config *config);
> +
>  #endif /* _IDIO_16_H_ */
> -- 
> 2.39.1
> 

-- 
With Best Regards,
Andy Shevchenko

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