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: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2020-10-06 10:10:20 +01:00
parent f4d51dffc6
commit 5556797662
2 changed files with 98 additions and 4 deletions

View File

@ -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;

View File

@ -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);