Subject: [RFC v2 02/12] PM / Domains: Support IRQ safe PM domains

From: [email-masked] (Stephen Boyd)
Date: Fri, 26 Feb 2016 10:17:53 -0800

On 02/12, Lina Iyer wrote:
> diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
> index 8ba6625..c06f0b6 100644
> --- a/Documentation/power/devices.txt
> +++ b/Documentation/power/devices.txt
> @@ -607,7 +607,16 @@ individually.  Instead, a set of devices sharing a power resource can be put
>  into a low-power state together at the same time by turning off the shared
>  power resource.  Of course, they also need to be put into the full-power state
>  together, by turning the shared power resource on.  A set of devices with this
> -property is often referred to as a power domain.
> +property is often referred to as a power domain. A power domain may also be
> +nested inside another power domain.
> +
> +Devices, by default, operate in process context and if a device can operate in
> +IRQ safe context, has to be explicitly set as IRQ safe. Power domains by

Devices, by default, operate in process context. If a device can
operate in IRQ safe context that has to be explicitly indicated
by setting the irq_safe boolean inside struct generic_pm_domain
to true. Power domains typically operate in process context...

> +default, operate in process context but could have devices that are IRQ safe.
> +Such power domains cannot be powered on/off during runtime PM. On the other
> +hand, an IRQ safe PM domains that have IRQ safe devices may be powered off

On the other hand, IRQ safe PM domains that have ..

> +when all the devices are in idle. An IRQ safe domain may only be attached as a

all the devices in the domain?

> +subdomain to another IRQ safe domain.
>  
>  Support for power domains is provided through the pm_domain field of struct
>  device.  This field is a pointer to an object of type struct dev_pm_domain,
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 8204615..3c4f675 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -75,11 +75,59 @@ static struct genpd_lock_fns irq_lock = {
>  	.unlock = genpd_unlock_irq,
>  };
>  
> +static void genpd_lock_nosleep(struct generic_pm_domain *genpd)
> +	__acquires(&genpd->slock)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&genpd->slock, flags);
> +	genpd->lock_flags = flags;
> +}
> +
> +static void genpd_lock_nosleep_nested(struct generic_pm_domain *genpd,
> +					int depth)
> +	__acquires(&genpd->slock)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave_nested(&genpd->slock, flags, depth);
> +	genpd->lock_flags = flags;
> +}
> +
> +static int genpd_lock_nosleep_interruptible(struct generic_pm_domain *genpd)
> +	__acquires(&genpd->slock)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&genpd->slock, flags);
> +	genpd->lock_flags = flags;
> +	return 0;

	genpd_lock_nosleep(genpd);
	return 0;

> +}
> +
> +static void genpd_unlock_nosleep(struct generic_pm_domain *genpd)
> +	__releases(&genpd->slock)
> +{
> +	spin_unlock_irqrestore(&genpd->slock, genpd->lock_flags);
> +}
> +
> +static struct genpd_lock_fns no_sleep_lock = {

const?

> +	.lock = genpd_lock_nosleep,
> +	.lock_nested = genpd_lock_nosleep_nested,
> +	.lock_interruptible = genpd_lock_nosleep_interruptible,
> +	.unlock = genpd_unlock_nosleep,
> +};
> +
>  #define genpd_lock(p)			p->lock_fns->lock(p)
>  #define genpd_lock_nested(p, d)		p->lock_fns->lock_nested(p, d)
>  #define genpd_lock_interruptible(p)	p->lock_fns->lock_interruptible(p)
>  #define genpd_unlock(p)			p->lock_fns->unlock(p)
>  
> +static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
> +		struct generic_pm_domain *genpd)
> +{
> +	return dev->power.irq_safe && !genpd->irq_safe;
> +}
> +
>  /*
>   * Get the generic PM domain for a particular struct device.
>   * This validates the struct device pointer, the PM domain pointer,
> @@ -510,8 +570,11 @@ static int pm_genpd_runtime_resume(struct device *dev)
>  	if (IS_ERR(genpd))
>  		return -EINVAL;
>  
> -	/* If power.irq_safe, the PM domain is never powered off. */
> -	if (dev->power.irq_safe) {
> +	/*
> +	 * As we dont power off a non IRQ safe domain, which holds

s/dont/don't/

> +	 * an IRQ safe device, we dont need to restore power to it.

s/dont/don't/

> +	 */
> +	if (dev->power.irq_safe && !genpd->irq_safe) {
>  		timed = false;
>  		goto out;
>  	}
> @@ -1296,6 +1359,13 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
>  	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev))
>  		return -EINVAL;
>  
> +	if (genpd->irq_safe && !dev->power.irq_safe) {
> +		dev_err(dev,
> +			"PM Domain %s is IRQ safe; device has to IRQ safe.\n",

has to be?

> +			genpd->name);
> +		return -EINVAL;
> +	}
> +
>  	gpd_data = genpd_alloc_dev_data(dev, genpd, td);
>  	if (IS_ERR(gpd_data))
>  		return PTR_ERR(gpd_data);
> @@ -1394,6 +1464,17 @@ int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
>  	    || genpd == subdomain)
>  		return -EINVAL;
>  
> +	/*
> +	 * If the domain can be powered on/off in an IRQ safe
> +	 * context, ensure that the subdomain can also be
> +	 * powered on/off in that context.
> +	 */
> +	if (!genpd->irq_safe && subdomain->irq_safe) {
> +		WARN("Parent %s of subdomain %s must be IRQ-safe\n",

Nitpick! IRQ-safe or IRQ safe? Use one consistently please.

> +				genpd->name, subdomain->name);
> +		return -EINVAL;
> +	}
> +
>  	link = kzalloc(sizeof(*link), GFP_KERNEL);
>  	if (!link)
>  		return -ENOMEM;

-- 
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