Commit 55567976 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

genirq/irqdomain: Allow partial trimming of irq_data hierarchy 



It appears that some HW is ugly enough that not all the interrupts
connected to a particular interrupt controller end up with the same
hierarchy depth (some of them are terminated early). This leaves
the irqchip hacker with only two choices, both equally bad:

- create discrete domain chains, one for each "hierarchy depth",
  which is very hard to maintain

- create fake hierarchy levels for the shallow paths, leading
  to all kind of problems (what are the safe hwirq values for these
  fake levels?)

Implement the ability to cut short a single interrupt hierarchy
from a level marked as being disconnected by using the new
irq_domain_disconnect_hierarchy() helper.

The irqdomain allocation code will then perform the trimming

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent f4d51dff

include/linux/irqdomain.h

+3 −0
Original line number Diff line number Diff line
@@ -509,6 +509,9 @@ extern void irq_domain_free_irqs_parent(struct irq_domain *domain, 
					unsigned int irq_base,

					unsigned int nr_irqs);



extern int irq_domain_disconnect_hierarchy(struct irq_domain *domain,

					   unsigned int virq);



static inline bool irq_domain_is_hierarchy(struct irq_domain *domain)

{

	return domain->flags & IRQ_DOMAIN_FLAG_HIERARCHY;

kernel/irq/irqdomain.c

+95 −4
Original line number Diff line number Diff line
@@ -1136,6 +1136,17 @@ static struct irq_data *irq_domain_insert_irq_data(struct irq_domain *domain, 
	return irq_data;

}



static void __irq_domain_free_hierarchy(struct irq_data *irq_data)

{

	struct irq_data *tmp;



	while (irq_data) {

		tmp = irq_data;

		irq_data = irq_data->parent_data;

		kfree(tmp);

	}

}



static void irq_domain_free_irq_data(unsigned int virq, unsigned int nr_irqs)

{

	struct irq_data *irq_data, *tmp;
@@ -1147,12 +1158,83 @@ static void irq_domain_free_irq_data(unsigned int virq, unsigned int nr_irqs) 
		irq_data->parent_data = NULL;

		irq_data->domain = NULL;



		while (tmp) {

			irq_data = tmp;

			tmp = tmp->parent_data;

			kfree(irq_data);

		__irq_domain_free_hierarchy(tmp);

	}

}



/**

 * irq_domain_disconnect_hierarchy - Mark the first unused level of a hierarchy

 * @domain:	IRQ domain from which the hierarchy is to be disconnected

 * @virq:	IRQ number where the hierarchy is to be trimmed

 *

 * Marks the @virq level belonging to @domain as disconnected.

 * Returns -EINVAL if @virq doesn't have a valid irq_data pointing

 * to @domain.

 *

 * Its only use is to be able to trim levels of hierarchy that do not

 * have any real meaning for this interrupt, and that the driver marks

 * as such from its .alloc() callback.

 */

int irq_domain_disconnect_hierarchy(struct irq_domain *domain,

				    unsigned int virq)

{

	struct irq_data *irqd;



	irqd = irq_domain_get_irq_data(domain, virq);

	if (!irqd)

		return -EINVAL;



	irqd->chip = ERR_PTR(-ENOTCONN);

	return 0;

}



static int irq_domain_trim_hierarchy(unsigned int virq)

{

	struct irq_data *tail, *irqd, *irq_data;



	irq_data = irq_get_irq_data(virq);

	tail = NULL;



	/* The first entry must have a valid irqchip */

	if (!irq_data->chip || IS_ERR(irq_data->chip))

		return -EINVAL;



	/*

	 * Validate that the irq_data chain is sane in the presence of

	 * a hierarchy trimming marker.

	 */

	for (irqd = irq_data->parent_data; irqd; irq_data = irqd, irqd = irqd->parent_data) {

		/* Can't have a valid irqchip after a trim marker */

		if (irqd->chip && tail)

			return -EINVAL;



		/* Can't have an empty irqchip before a trim marker */

		if (!irqd->chip && !tail)

			return -EINVAL;



		if (IS_ERR(irqd->chip)) {

			/* Only -ENOTCONN is a valid trim marker */

			if (PTR_ERR(irqd->chip) != -ENOTCONN)

				return -EINVAL;



			tail = irq_data;

		}

	}



	/* No trim marker, nothing to do */

	if (!tail)

		return 0;



	pr_info("IRQ%d: trimming hierarchy from %s\n",

		virq, tail->parent_data->domain->name);



	/* Sever the inner part of the hierarchy...  */

	irqd = tail;

	tail = tail->parent_data;

	irqd->parent_data = NULL;

	__irq_domain_free_hierarchy(tail);



	return 0;

}



static int irq_domain_alloc_irq_data(struct irq_domain *domain,
@@ -1362,6 +1444,15 @@ int __irq_domain_alloc_irqs(struct irq_domain *domain, int irq_base, 
		mutex_unlock(&irq_domain_mutex);

		goto out_free_irq_data;

	}



	for (i = 0; i < nr_irqs; i++) {

		ret = irq_domain_trim_hierarchy(virq + i);

		if (ret) {

			mutex_unlock(&irq_domain_mutex);

			goto out_free_irq_data;

		}

	}

	

	for (i = 0; i < nr_irqs; i++)

		irq_domain_insert_irq(virq + i);

	mutex_unlock(&irq_domain_mutex);

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