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 the first level that doesn't have a corresponding irqchip.
As this is never a valid option (we have the no_irq_chip chip
for the "do nothing" case), the hierarchy can be trimmed from
that level.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
kernel/irq/irqdomain.c | 58 +++++++++++++++++++++++++++++++++++++-----
1 file changed, 52 insertions(+), 6 deletions(-)
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 76cd7ebd1178..375eb2b79fe5 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -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;
@@ -1147,14 +1158,47 @@ 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_trim_hierarchy - Trim the uninitialized part of a irq hierarchy
+ * @virq: IRQ number to trim where the hierarchy is to be trimmed
+ *
+ * Drop the partial irq_data hierarchy from the level where the
+ * irq_data->chip is NULL.
+ *
+ * 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 leaves
+ * uninitialized in its .alloc() callback.
+ */
+static void irq_domain_trim_hierarchy(unsigned int virq)
+{
+ struct irq_data *tail, *irq_data = irq_get_irq_data(virq);
+
+ /* It really needs to be a hierarchy, and not a single entry */
+ if (!irq_data->parent_data)
+ return;
+
+ /* Skip until we find a parent irq_data without a populated chip */
+ while (irq_data->parent_data && irq_data->parent_data->chip)
+ irq_data = irq_data->parent_data;
+
+ /* All levels populated */
+ if (!irq_data->parent_data)
+ return;
+
+ pr_info("IRQ%d: trimming hierarchy from %s\n",
+ virq, irq_data->parent_data->domain->name);
+
+ /* Sever the inner part of the hierarchy... */
+ tail = irq_data->parent_data;
+ irq_data->parent_data = NULL;
+ __irq_domain_free_hierarchy(tail);
+}
+
+
static int irq_domain_alloc_irq_data(struct irq_domain *domain,
unsigned int virq, unsigned int nr_irqs)
{
@@ -1362,8 +1406,10 @@ 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++)
+ for (i = 0; i < nr_irqs; i++) {
+ irq_domain_trim_hierarchy(virq + i);
irq_domain_insert_irq(virq + i);
+ }
mutex_unlock(&irq_domain_mutex);
return virq;
--
2.28.0
