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Message-ID: <9341eb039193d630d8a3f7bac920a76c@kernel.org>
Date: Thu, 08 Oct 2020 14:06:19 +0100
From: Marc Zyngier <maz@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Thierry Reding <thierry.reding@...il.com>,
Jonathan Hunter <jonathanh@...dia.com>,
Dmitry Osipenko <digetx@...il.com>,
Sowjanya Komatineni <skomatineni@...dia.com>,
Venkat Reddy Talla <vreddytalla@...dia.com>,
kernel-team@...roid.com
Subject: Re: [PATCH v3 1/4] genirq/irqdomain: Allow partial trimming of
irq_data hierarchy
On 2020-10-08 12:22, Thomas Gleixner wrote:
> On Wed, Oct 07 2020 at 13:45, Marc Zyngier wrote:
>> +/**
>> + * 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);
>> +}
>
> I like that way more than the previous version, but there are still
> quite some dangeroos waiting to bite.
>
> Just for robustness sake we should do the following:
[...]
Here's what I have now, with the pmc driver calling
irq_domain_disconnect_hierarchy() at the right spots.
M.
diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index b37350c4fe37..a52b095bd404 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -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;
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 76cd7ebd1178..316f5baa9cd9 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;
@@ -1147,12 +1158,81 @@ 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);
+ }
+}
+
+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;
+}
+
+/**
+ * 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 a trim marker (PTR_ERR(-ENOTCONN)).
+ *
+ * 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.
+ */
+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,
@@ -1362,11 +1442,16 @@ 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++) {
+ ret = irq_domain_trim_hierarchy(virq + i);
+ if (ret)
+ break;
irq_domain_insert_irq(virq + i);
+ }
mutex_unlock(&irq_domain_mutex);
- return virq;
+ if (!ret)
+ return virq;
out_free_irq_data:
irq_domain_free_irq_data(virq, nr_irqs);
--
Jazz is not dead. It just smells funny...
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