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 <[email protected]> --- 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
