genirq/generic_chip: Introduce init() and exit() hooks

Most of generic chip drivers need to perform some more additional
initializations on the generic chips allocated before they can be fully
ready.

These additional initializations need to be performed before the IRQ
domain is published to avoid a race condition between IRQ consumers and
suppliers.

Introduce the init() hook to perform these initializations at the right
place just after the generic chip creation. Also introduce the exit() hook
to allow reverting operations done by the init() hook just before the
generic chip is destroyed.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240614173232.1184015-15-herve.codina@bootlin.com

include/linux/irq.h

@@ -1106,6 +1106,7 @@ enum irq_gc_flags {
  * @irq_flags_to_set:	IRQ* flags to set on irq setup
  * @irq_flags_to_clear:	IRQ* flags to clear on irq setup
  * @gc_flags:		Generic chip specific setup flags
+ * @exit:		Function called on each chip when they are destroyed.
  * @gc:			Array of pointers to generic interrupt chips
  */
 struct irq_domain_chip_generic {
@@ -1114,6 +1115,7 @@ struct irq_domain_chip_generic {
 	unsigned int		irq_flags_to_clear;
 	unsigned int		irq_flags_to_set;
 	enum irq_gc_flags	gc_flags;
+	void			(*exit)(struct irq_chip_generic *gc);
 	struct irq_chip_generic	*gc[];
 };
 
@@ -1127,6 +1129,10 @@ struct irq_domain_chip_generic {
  * @irq_flags_to_clear:	IRQ_* bits to clear in the mapping function
  * @irq_flags_to_set:	IRQ_* bits to set in the mapping function
  * @gc_flags:		Generic chip specific setup flags
+ * @init:		Function called on each chip when they are created.
+ *			Allow to do some additional chip initialisation.
+ * @exit:		Function called on each chip when they are destroyed.
+ *			Allow to do some chip cleanup operation.
  */
 struct irq_domain_chip_generic_info {
 	const char		*name;
@@ -1136,6 +1142,8 @@ struct irq_domain_chip_generic_info {
 	unsigned int		irq_flags_to_clear;
 	unsigned int		irq_flags_to_set;
 	enum irq_gc_flags	gc_flags;
+	int			(*init)(struct irq_chip_generic *gc);
+	void			(*exit)(struct irq_chip_generic *gc);
 };
 
 /* Generic chip callback functions */

kernel/irq/generic-chip.c

@@ -293,6 +293,7 @@ int irq_domain_alloc_generic_chips(struct irq_domain *d,
 	size_t gc_sz;
 	size_t sz;
 	void *tmp;
+	int ret;
 
 	if (d->gc)
 		return -EBUSY;
@@ -314,6 +315,7 @@ int irq_domain_alloc_generic_chips(struct irq_domain *d,
 	dgc->irq_flags_to_set = info->irq_flags_to_set;
 	dgc->irq_flags_to_clear = info->irq_flags_to_clear;
 	dgc->gc_flags = info->gc_flags;
+	dgc->exit = info->exit;
 	d->gc = dgc;
 
 	/* Calc pointer to the first generic chip */
@@ -331,6 +333,12 @@ int irq_domain_alloc_generic_chips(struct irq_domain *d,
 			gc->reg_writel = &irq_writel_be;
 		}
 
+		if (info->init) {
+			ret = info->init(gc);
+			if (ret)
+				goto err;
+		}
+
 		raw_spin_lock_irqsave(&gc_lock, flags);
 		list_add_tail(&gc->list, &gc_list);
 		raw_spin_unlock_irqrestore(&gc_lock, flags);
@@ -338,6 +346,16 @@ int irq_domain_alloc_generic_chips(struct irq_domain *d,
 		tmp += gc_sz;
 	}
 	return 0;
+
+err:
+	while (i--) {
+		if (dgc->exit)
+			dgc->exit(dgc->gc[i]);
+		irq_remove_generic_chip(dgc->gc[i], ~0U, 0, 0);
+	}
+	d->gc = NULL;
+	kfree(dgc);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(irq_domain_alloc_generic_chips);
 
@@ -353,9 +371,11 @@ void irq_domain_remove_generic_chips(struct irq_domain *d)
 	if (!dgc)
 		return;
 
-	for (i = 0; i < dgc->num_chips; i++)
+	for (i = 0; i < dgc->num_chips; i++) {
+		if (dgc->exit)
+			dgc->exit(dgc->gc[i]);
 		irq_remove_generic_chip(dgc->gc[i], ~0U, 0, 0);
-
+	}
 	d->gc = NULL;
 	kfree(dgc);
 }