Date:	Fri, 06 Mar 2015 03:02:05 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Tony Lindgren <tony@...mide.com>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Andreas Fenkart <afenkart@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>,
	Huiquan Zhong <huiquan.zhong@...el.com>,
	Kevin Hilman <khilman@...nel.org>, NeilBrown <neilb@...e.de>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Nishanth Menon <nm@...com>,
	Peter Hurley <peter@...leysoftware.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-omap@...r.kernel.org,
	Linux PM list <linux-pm@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH 1/4] PM / Wakeirq: Add minimal device wakeirq helper functions

Please always CC linux-pm on CC patches.

On Thursday, March 05, 2015 04:34:06 PM Tony Lindgren wrote:
> Some devices have separate wake-up interrupts in addition to the
> normal device interrupts. The wake-up interrupts can be connected
> to a separate interrupt controller that is always powered. This
> allows the devices and the whole system to enter deeper idle states
> while still being able to wake-up to events.
> 
> As some devices are already using wake-up interrupts, let's add
> some helper functions. This is to avoid having the drivers getting
> things wrong in a different ways. Some of these drivers also have
> a interrupt re-entrancy problem as the normal device interrupt
> handler is being called from the wake-up interrupt as pointed out
> by Thomas Gleixner <tglx@...utronix.de>.

We need to talk a bit about the design here IMO.

I need to have a look at this tomorrow or over the weekend and not in the
middle of the night in particular.

Some comments below, but I may be overlooking things ATM.

> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
>  arch/arm/mach-omap2/Kconfig  |   1 +
>  drivers/base/power/Makefile  |   1 +
>  drivers/base/power/wakeirq.c | 201 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm_wakeirq.h   |  69 +++++++++++++++
>  kernel/power/Kconfig         |   4 +
>  5 files changed, 276 insertions(+)
>  create mode 100644 drivers/base/power/wakeirq.c
>  create mode 100644 include/linux/pm_wakeirq.h
> 
> diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
> index 2b8e477..f3e9b88 100644
> --- a/arch/arm/mach-omap2/Kconfig
> +++ b/arch/arm/mach-omap2/Kconfig
> @@ -83,6 +83,7 @@ config ARCH_OMAP2PLUS
>  	select OMAP_DM_TIMER
>  	select OMAP_GPMC
>  	select PINCTRL
> +	select PM_WAKEIRQ
>  	select SOC_BUS
>  	select TI_PRIV_EDMA
>  	select OMAP_IRQCHIP
> diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
> index 1cb8544..527546e 100644
> --- a/drivers/base/power/Makefile
> +++ b/drivers/base/power/Makefile
> @@ -4,5 +4,6 @@ obj-$(CONFIG_PM_TRACE_RTC)	+= trace.o
>  obj-$(CONFIG_PM_OPP)	+= opp.o
>  obj-$(CONFIG_PM_GENERIC_DOMAINS)	+=  domain.o domain_governor.o
>  obj-$(CONFIG_HAVE_CLK)	+= clock_ops.o
> +obj-$(CONFIG_PM_WAKEIRQ)	+= wakeirq.o
>  
>  ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
> diff --git a/drivers/base/power/wakeirq.c b/drivers/base/power/wakeirq.c
> new file mode 100644
> index 0000000..566d69d
> --- /dev/null
> +++ b/drivers/base/power/wakeirq.c
> @@ -0,0 +1,201 @@
> +/*
> + * wakeirq.c - Device wakeirq helper functions
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/pm_wakeirq.h>
> +
> +/**
> + * handle_dedicated_wakeirq - Handler for device wake-up interrupts
> + * @wakeirq: Separate wake-up interrupt for a device different
> + * @_wirq: Wake-up interrupt data
> + *
> + * Some devices have a separate wake-up interrupt in addition to the
> + * regular device interrupt. The wake-up interrupts signal that the
> + * device should be woken up from a deeper idle state. This handler
> + * uses device specific pm_runtime functions to wake-up the device
> + * and then it's up to the device to do whatever it needs to. Note
> + * as the device may need to restore context and start up regulators,
> + * this is not a fast path.
> + *
> + * Note that we are not resending the lost device interrupts. We assume
> + * that the wake-up interrupt just needs to wake-up the device, and
> + * the device pm_runtime_resume() can deal with the situation.
> + */
> +static irqreturn_t handle_dedicated_wakeirq(int wakeirq, void *_wirq)
> +{
> +	struct wakeirq_source *wirq = _wirq;
> +	irqreturn_t ret = IRQ_NONE;
> +
> +	/* We don't want RPM_ASYNC or RPM_NOWAIT here */
> +	if (pm_runtime_suspended(wirq->dev)) {

What if the device is resumed on a different CPU right here?

> +		pm_runtime_mark_last_busy(wirq->dev);
> +		pm_runtime_resume(wirq->dev);

Calling this with disabled interrupts is a bad idea in general.
Is the device guaranteed to have power.irq_safe set?

I guess what you want to call here is pm_request_resume() and
I wouldn't say that calling pm_runtime_mark_last_busy() on a
suspended device was valid.

> +		ret = IRQ_HANDLED;
> +	}
> +
> +	if (wirq->handler)
> +		ret = wirq->handler(wakeirq, wirq->data);
> +
> +	return ret;
> +}
> +
> +static void dev_pm_wakeirq_init(struct device *dev,
> +				struct wakeirq_source *wirq)
> +{
> +	wirq->dev = dev;
> +	wirq->wakeirq = -EINVAL;
> +	wirq->handler = NULL;
> +	wirq->data = NULL;
> +	wirq->initialized = true;
> +}
> +
> +/**
> + * dev_pm_wakeirq_request - Request a wake-up interrupt
> + * @dev: Device dev entry
> + * @wakeirq: Device wake-up interrupt
> + * @handler: Optional device specific handler
> + * @irqflags: Optional irqflags, IRQF_ONESHOT if not specified
> + * @data: Optional device specific data
> + * @wirq: Wake-up irq data
> + *
> + * Sets up a threaded interrupt handler for a device that
> + * by default just wakes up the device on a wake-up interrupt.
> + * The interrupt starts disabled, and needs to be managed for
> + * the device by the bus code or the device driver using
> + * dev_pm_wakeirq_enable() and dev_pm_wakeirq_disable()
> + * functions.
> + */
> +int dev_pm_wakeirq_request(struct device *dev,
> +			   int wakeirq,
> +			   irq_handler_t handler,
> +			   unsigned long irqflags,
> +			   void *data,
> +			   struct wakeirq_source *wirq)
> +{
> +	int err;
> +
> +	if (!dev || !wirq)
> +		return -EINVAL;
> +
> +	if (!wirq->initialized)
> +		dev_pm_wakeirq_init(dev, wirq);
> +
> +	if (!irqflags)
> +		irqflags = IRQF_ONESHOT;
> +
> +	irq_set_status_flags(wakeirq, IRQ_NOAUTOEN);
> +
> +	/*
> +	 * Consumer device may need to power up and restore state
> +	 * so let's just use threaded irq.
> +	 */
> +	err = devm_request_threaded_irq(wirq->dev,
> +					wakeirq,
> +					handler,
> +					handle_dedicated_wakeirq,
> +					irqflags,
> +					dev_name(wirq->dev),
> +					wirq);
> +	if (err)
> +		return err;
> +
> +	wirq->wakeirq = wakeirq;
> +	wirq->handler = handler;
> +	wirq->data = data;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_wakeirq_request);
> +
> +static int is_valid_wakeirq(struct wakeirq_source *wirq)
> +{
> +	return wirq && wirq->initialized && (wirq->wakeirq >= 0);
> +}
> +
> +#define is_invalid_wakeirq(w)	!is_valid_wakeirq(w)
> +
> +/**
> + * dev_pm_wakeirq_free - Free a wake-up interrupt
> + * @wirq: Device wake-up interrupt
> + */
> +void dev_pm_wakeirq_free(struct wakeirq_source *wirq)
> +{
> +	if (is_invalid_wakeirq(wirq))
> +		return;
> +
> +	devm_free_irq(wirq->dev, wirq->wakeirq, wirq);
> +	wirq->wakeirq = -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_wakeirq_free);
> +
> +/**
> + * dev_pm_wakeirq_enable - Enable device wake-up interrupt
> + * @wirq: Device wake-up interrupt
> + *
> + * Called from the bus code or the device driver for
> + * runtime_suspend() to enable the wake-up interrupt while
> + * the device is running.
> + *
> + * Note that for runtime_suspend()) the wake-up interrupts
> + * should be unconditionally enabled unlike for suspend()
> + * that is conditional.
> + */
> +void dev_pm_wakeirq_enable(struct wakeirq_source *wirq)
> +{
> +	if (is_invalid_wakeirq(wirq))
> +		return;
> +
> +	enable_irq(wirq->wakeirq);
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_wakeirq_enable);
> +
> +/**
> + * dev_pm_wakeirq_disable - Disable device wake-up interrupt
> + * @wirq: Device wake-up interrupt
> + *
> + * Called from the bus code or the device driver for
> + * runtime_resume() to disable the wake-up interrupt while
> + * the device is running.
> + */
> +void dev_pm_wakeirq_disable(struct wakeirq_source *wirq)
> +{
> +	if (is_invalid_wakeirq(wirq))
> +		return;
> +
> +	disable_irq_nosync(wirq->wakeirq);
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_wakeirq_disable);
> +
> +/**
> + * dev_pm_wakeirq_arm_for_suspend - Configure device wake-up
> + * @wirq: Device wake-up interrupt
> + *
> + * Called from the bus code or the device driver for
> + * device suspend(). Just sets up the wake-up event
> + * conditionally based on the device_may_wake(). The
> + * rest is handled automatically by the generic suspend()
> + * code and runtime_suspend().
> + */
> +void dev_pm_wakeirq_arm_for_suspend(struct wakeirq_source *wirq)
> +{
> +	if (is_invalid_wakeirq(wirq))
> +		return;
> +
> +	irq_set_irq_wake(wirq->wakeirq,
> +			 device_may_wakeup(wirq->dev));

You want to do

	if (device_may_wakeup(wirq->dev))
		enable_irq_wake(wirq->wakeirq);

here or strange things may happen if two devices share a wakeup IRQ.

Also instead of doing it this way, I'd prefer to hook system wakeup
interrupts into the wakeup source objects pointed to by the power.wakeup
fields in struct device.

Then we could just walk the list of wakeup sources and do enable_irq_wake()
automatically for the wakeup interrupts hooked up to them at the
suspend_device_irqs() time without the need to do anything from drivers
at suspend time.

> +}
> +EXPORT_SYMBOL_GPL(dev_pm_wakeirq_arm_for_suspend);
> +
> diff --git a/include/linux/pm_wakeirq.h b/include/linux/pm_wakeirq.h
> new file mode 100644
> index 0000000..3ecbc1a
> --- /dev/null
> +++ b/include/linux/pm_wakeirq.h
> @@ -0,0 +1,69 @@
> +/*
> + * pm_wakeirq.h - Device wakeirq helper functions
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef _LINUX_PM_WAKEIRQ_H
> +#define _LINUX_PM_WAKEIRQ_H
> +
> +struct wakeirq_source {
> +	struct device *dev;
> +	int wakeirq;
> +	bool initialized;
> +	bool enabled;
> +	irq_handler_t handler;
> +	void *data;
> +};

Well, so now we have struct wakeup_source already and here we get struct wakeirq_source
and they mean different things ...

> +
> +#ifdef CONFIG_PM_WAKEIRQ
> +
> +extern int dev_pm_wakeirq_request(struct device *dev,
> +				  int wakeirq,
> +				  irq_handler_t handler,
> +				  unsigned long irqflags,
> +				  void *data,
> +				  struct wakeirq_source *wirq);
> +extern void dev_pm_wakeirq_free(struct wakeirq_source *wirq);
> +extern void dev_pm_wakeirq_enable(struct wakeirq_source *wirq);
> +extern void dev_pm_wakeirq_disable(struct wakeirq_source *wirq);
> +extern void dev_pm_wakeirq_arm_for_suspend(struct wakeirq_source *wirq);
> +
> +#else	/* !CONFIG_PM_WAKEIRQ */
> +
> +static inline int dev_pm_wakeirq_request(struct device *dev,
> +					 int wakeirq,
> +					 irq_handler_t handler,
> +					 unsigned long irqflags,
> +					 void *data,
> +					 struct wakeirq_source *wirq)
> +{
> +	return 0;
> +}
> +
> +static inline void dev_pm_wakeirq_free(struct wakeirq_source *wirq)
> +{
> +}
> +
> +static inline void dev_pm_wakeirq_enable(struct wakeirq_source *wirq)
> +{
> +}
> +
> +static inline void dev_pm_wakeirq_disable(struct wakeirq_source *wirq)
> +{
> +}
> +
> +static inline void
> +dev_pm_wakeirq_arm_for_suspend(struct wakeirq_source *wirq)
> +{
> +}
> +
> +#endif	/* CONFIG_PM_WAKEIRQ */
> +#endif	/* _LINUX_PM_WAKEIRQ_H */
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 7e01f78..c249845 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -267,6 +267,10 @@ config PM_CLK
>  	def_bool y
>  	depends on PM && HAVE_CLK
>  
> +config PM_WAKEIRQ
> +	bool
> +	depends on PM
> +
>  config PM_GENERIC_DOMAINS
>  	bool
>  	depends on PM
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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