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Date: Fri, 3 Oct 2008 10:38:19 +0300
From: Tony Lindgren <tony@...mide.com>
To: David Brownell <david-b@...bell.net>
Cc: lkml <linux-kernel@...r.kernel.org>,
Haavard Skinnemoen <hskinnemoen@...el.com>,
Andrew Victor <linux@...im.org.za>,
Kevin Hilman <khilman@...prootsystems.com>
Subject: Re: [PATCH/RFC] hardware irq debouncing support
* David Brownell <david-b@...bell.net> [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@...mide.com>
>
> ---
> 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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