Re: [PATCH/RFC] hardware irq debouncing support

[Tony Lindgren]

* David Brownell <david-b@xxxxxxxxxxx> [080924 22:51]:
> Hardware IRQ debouncing is common for IRQ controllers which are
> part of GPIO modules ... they often deal with mechanical switches,
> buttons, and so forth.  This patch:
> 
>  - Provides simple support for that in genirq
> 
>  - Includes sample implementations for some Linux systems
>    which already include non-generic support for this:
> 
>      * Atmel SOCs (AT91, AT32 -- the same GPIO module)
>      * OMAP2/OMAP3 (not quite as simple)
>
> Control over how long to debounce is less common, and often applies
> to banks of GPIOs not individual signals ... not addressed here.
> 
> Drivers can request this (where available) with a new IRQF_DEBOUNCED
> flag/hint passed to request_irq():
> 
>     IF that flag is set when a handler is registered
> 	AND the relevant irq_chip supports debouncing
> 	AND the IRQ isn't already flagged as being debounced
>     THEN the irq_chip is asked to enable debouncing for this IRQ
> 	UNTIL the IRQ's last handler is unregistered.
>     ELSE
>         nothing is done ... the hint is ignored
>     FI
> 
> Comments?
> 
> Having this mechanism in genirq would let boards remove a bunch of
> nonportable code, and would let drivers like gpio_keys, gpio_mouse,
> and various touchscreens work more reliably.  It'd also let various
> SOC-specific MMC and CF card drivers switch over to more standard
> (and widely understandable) mechanisms.

Yeah this would nuke bunch of omap specific code for dealing with
battery covers, MMC slot open etc..

> I'd like to submit such updates for the 2.6.28 merge window, in
> part to let mainline avoid needing yet another driver-specific
> programming interface for IRQ debouncing.  (For TWL4030/TPS659x0,
> as used in most OMAP3 boards including the Gumstix Overo and the
> BeagleBoard.)

What's the plan for sysfs_notify event for these switches? Are you
planning to add something like that to gpiolib?

Tony


> p.s. Tony and Kevin:  note the locking bugfix in the OMAP2/3 bit.

Here's my ack for that:

Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>

> 
> ---
>  arch/arm/mach-at91/gpio.c    |   13 +++++++++++++
>  arch/arm/plat-omap/gpio.c    |   15 ++++++++++++++-
>  arch/avr32/mach-at32ap/pio.c |   14 ++++++++++++++
>  include/linux/interrupt.h    |    2 ++
>  include/linux/irq.h          |    3 +++
>  kernel/irq/manage.c          |   27 +++++++++++++++++++++++++++
>  6 files changed, 73 insertions(+), 1 deletion(-)
> 
> --- a/arch/arm/mach-at91/gpio.c
> +++ b/arch/arm/mach-at91/gpio.c
> @@ -368,12 +368,25 @@ static int gpio_irq_type(unsigned pin, u
>  	}
>  }
>  
> +static int gpio_irq_debounce(unsigned pin, bool is_on)
> +{
> +	void __iomem	*pio = pin_to_controller(pin);
> +	unsigned	mask = pin_to_mask(pin);
> +
> +	if (is_on)
> +		__raw_writel(mask, pio + PIO_IFER);
> +	else
> +		__raw_writel(mask, pio + PIO_IFDR);
> +	return 0;
> +}
> +
>  static struct irq_chip gpio_irqchip = {
>  	.name		= "GPIO",
>  	.mask		= gpio_irq_mask,
>  	.unmask		= gpio_irq_unmask,
>  	.set_type	= gpio_irq_type,
>  	.set_wake	= gpio_irq_set_wake,
> +	.debounce	= gpio_irq_debounce,
>  };
>  
>  static void gpio_irq_handler(unsigned irq, struct irq_desc *desc)
> --- a/arch/arm/plat-omap/gpio.c
> +++ b/arch/arm/plat-omap/gpio.c
> @@ -472,6 +472,7 @@ void omap_set_gpio_debounce(int gpio, in
>  {
>  	struct gpio_bank *bank;
>  	void __iomem *reg;
> +	unsigned long flags;
>  	u32 val, l = 1 << get_gpio_index(gpio);
>  
>  	if (cpu_class_is_omap1())
> @@ -479,8 +480,9 @@ void omap_set_gpio_debounce(int gpio, in
>  
>  	bank = get_gpio_bank(gpio);
>  	reg = bank->base;
> -
>  	reg += OMAP24XX_GPIO_DEBOUNCE_EN;
> +
> +	spin_lock_irqsave(&bank->lock, flags);
>  	val = __raw_readl(reg);
>  
>  	if (enable)
> @@ -489,6 +491,7 @@ void omap_set_gpio_debounce(int gpio, in
>  		val &= ~l;
>  
>  	__raw_writel(val, reg);
> +	spin_unlock_irqrestore(&bank->lock, flags);
>  }
>  EXPORT_SYMBOL(omap_set_gpio_debounce);
>  
> @@ -1109,6 +1112,12 @@ static void gpio_unmask_irq(unsigned int
>  	_set_gpio_irqenable(bank, gpio, 1);
>  }
>  
> +static int gpio_irq_debounce(unsigned int irq, bool is_on)
> +{
> +	omap_set_gpio_debounce(irq - IH_GPIO_BASE, is_on);
> +	return 0;
> +}
> +
>  static struct irq_chip gpio_irq_chip = {
>  	.name		= "GPIO",
>  	.shutdown	= gpio_irq_shutdown,
> @@ -1437,6 +1446,10 @@ static int __init _omap_gpio_init(void)
>  			(rev >> 4) & 0x0f, rev & 0x0f);
>  	}
>  #endif
> +
> +	if (cpu_is_omap242x() || cpu_is_omap243x() || cpu_is_omap34xx())
> +		gpio_irq_chip.debounce = gpio_irq_debounce;
> +
>  	for (i = 0; i < gpio_bank_count; i++) {
>  		int j, gpio_count = 16;
>  
> --- a/arch/avr32/mach-at32ap/pio.c
> +++ b/arch/avr32/mach-at32ap/pio.c
> @@ -234,11 +234,25 @@ static int gpio_irq_type(unsigned irq, u
>  	return 0;
>  }
>  
> +static int gpio_irq_debounce(unsigned irq, bool is_on)
> +{
> +	unsigned		gpio = irq_to_gpio(irq);
> +	struct pio_device	*pio = &pio_dev[gpio >> 5];
> +	u32			mask = 1 << (gpio & 0x1f);
> +
> +	if (is_on)
> +		pio_writel(pio, IFER, mask);
> +	else
> +		pio_writel(pio, IFDR, mask);
> +	return 0;
> +}
> +
>  static struct irq_chip gpio_irqchip = {
>  	.name		= "gpio",
>  	.mask		= gpio_irq_mask,
>  	.unmask		= gpio_irq_unmask,
>  	.set_type	= gpio_irq_type,
> +	.debounce	= gpio_irq_debounce,
>  };
>  
>  static void gpio_irq_handler(unsigned irq, struct irq_desc *desc)
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -45,6 +45,7 @@
>   * IRQF_IRQPOLL - Interrupt is used for polling (only the interrupt that is
>   *                registered first in an shared interrupt is considered for
>   *                performance reasons)
> + * IRQF_DEBOUNCED - Interrupt should use hardware debouncing where possible
>   */
>  #define IRQF_DISABLED		0x00000020
>  #define IRQF_SAMPLE_RANDOM	0x00000040
> @@ -54,6 +55,7 @@
>  #define IRQF_PERCPU		0x00000400
>  #define IRQF_NOBALANCING	0x00000800
>  #define IRQF_IRQPOLL		0x00001000
> +#define IRQF_DEBOUNCED		0x00002000
>  
>  typedef irqreturn_t (*irq_handler_t)(int, void *);
>  
> --- a/include/linux/irq.h
> +++ b/include/linux/irq.h
> @@ -44,6 +44,7 @@ typedef	void (*irq_flow_handler_t)(unsig
>  #define IRQ_TYPE_LEVEL_LOW	0x00000008	/* Level low type */
>  #define IRQ_TYPE_SENSE_MASK	0x0000000f	/* Mask of the above */
>  #define IRQ_TYPE_PROBE		0x00000010	/* Probing in progress */
> +#define IRQ_TYPE_DEBOUNCED	0x00000020	/* Hardware debouncing enabled */
>  
>  /* Internal flags */
>  #define IRQ_INPROGRESS		0x00000100	/* IRQ handler active - do not enter! */
> @@ -92,6 +93,7 @@ struct msi_desc;
>   * @retrigger:		resend an IRQ to the CPU
>   * @set_type:		set the flow type (IRQ_TYPE_LEVEL/etc.) of an IRQ
>   * @set_wake:		enable/disable power-management wake-on of an IRQ
> + * @debounce:		enable/disable hardware debouncing of an IRQ
>   *
>   * @release:		release function solely used by UML
>   * @typename:		obsoleted by name, kept as migration helper
> @@ -114,6 +116,7 @@ struct irq_chip {
>  	int		(*retrigger)(unsigned int irq);
>  	int		(*set_type)(unsigned int irq, unsigned int flow_type);
>  	int		(*set_wake)(unsigned int irq, unsigned int on);
> +	int		(*debounce)(unsigned int irq, bool is_on);
>  
>  	/* Currently used only by UML, might disappear one day.*/
>  #ifdef CONFIG_IRQ_RELEASE_METHOD
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -445,6 +445,18 @@ int setup_irq(unsigned int irq, struct i
>  	desc->irq_count = 0;
>  	desc->irqs_unhandled = 0;
>  
> +	/* Maybe enable hardware debouncing */
> +	if ((new->flags & IRQF_DEBOUNCED)
> +			&& desc->chip->debounce
> +			&& !(desc->status & IRQ_TYPE_DEBOUNCED)) {
> +		ret = desc->chip->debounce(irq, true);
> +		if (ret < 0)
> +			pr_debug("IRQ: can't debounce irq %d, err %d\n",
> +					irq, ret);
> +		else
> +			desc->status |= IRQ_TYPE_DEBOUNCED;
> +	}
> +
>  	/*
>  	 * Check whether we disabled the irq via the spurious handler
>  	 * before. Reenable it and give it another chance.
> @@ -524,6 +536,21 @@ void free_irq(unsigned int irq, void *de
>  
>  			if (!desc->action) {
>  				desc->status |= IRQ_DISABLED;
> +
> +				/* Maybe disable hardware debouncing */
> +				if ((desc->status & IRQ_TYPE_DEBOUNCED)
> +						&& desc->chip->debounce) {
> +					int status;
> +
> +					status = desc->chip->debounce(irq, false);
> +					if (status < 0)
> +						pr_debug("IRQ: irq %d still "
> +							"being debounced, err %d\n",
> +							irq, status);
> +					else
> +						desc->status &= ~IRQ_TYPE_DEBOUNCED;
> +				}
> +
>  				if (desc->chip->shutdown)
>  					desc->chip->shutdown(irq);
>  				else
--
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