[RFC] powerpc/irq: Add generic API for setting up cascaded IRQs

[Grant Likely]

From: Grant Likely <grant.likely at secretlab.ca>

prototype implementation.  This probably doesn't work at all right now.

Ben, I'm posting this now to get your thoughts before I go too far down
this path.

Cheers,
g.

---

 arch/powerpc/include/asm/irq.h            |    3 ++
 arch/powerpc/kernel/irq.c                 |   20 +++++++++++++++
 arch/powerpc/platforms/52xx/mpc52xx_pic.c |   39 +++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 0 deletions(-)


diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index 0a51376..014e1e8 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -90,6 +90,9 @@ struct irq_host_ops {
 	/* Update of such a mapping  */
 	void (*remap)(struct irq_host *h, unsigned int virq, irq_hw_number_t hw);
 
+	/* Setup hook for cascade irqs */
+	int (*cascade_setup)(int virq, int (*get_irq)(void *data), void *data);
+
 	/* Translate device-tree interrupt specifier from raw format coming
 	 * from the firmware to a irq_hw_number_t (interrupt line number) and
 	 * type (sense) that can be passed to set_irq_type(). In the absence
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index f7f376e..5a9cb46 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -750,6 +750,26 @@ unsigned int irq_of_parse_and_map(struct device_node *dev, int index)
 }
 EXPORT_SYMBOL_GPL(irq_of_parse_and_map);
 
+unsigned int irq_of_cascade_setup(int virq, int (*get_irq)(void *data),
+				  void *data)
+{
+	struct irq_host *host = irq_map[virq].host;
+
+	if (!host) {
+		pr_err("error: no irq host found virq %i !\n", virq);
+		return -ENODEV;
+	}
+
+	/* If host has no cascade setup function, then this method for
+	 * setting up a cascade is not available */
+	if (!host->ops->cascade_setup) {
+		pr_err("error: no cascade_setup support on virq %i\n", virq);
+		return -EINVAL;
+	}
+
+	return host->ops->cascade_setup(virq, get_irq, data);
+}
+
 void irq_dispose_mapping(unsigned int virq)
 {
 	struct irq_host *host;
diff --git a/arch/powerpc/platforms/52xx/mpc52xx_pic.c b/arch/powerpc/platforms/52xx/mpc52xx_pic.c
index 480f806..a91c69b 100644
--- a/arch/powerpc/platforms/52xx/mpc52xx_pic.c
+++ b/arch/powerpc/platforms/52xx/mpc52xx_pic.c
@@ -437,9 +437,48 @@ static int mpc52xx_irqhost_map(struct irq_host *h, unsigned int virq,
 	return 0;
 }
 
+struct mpc52xx_cascade_data {
+	int (*get_irq)(void *data);
+	void *data;
+};
+
+void mpc52xx_handle_level_cascade(unsigned int irq, struct irq_desc *desc)
+{
+	struct mpc52xx_cascade_data *cascade_data = get_irq_desc_data(desc);
+	int cascade_virq;
+
+	cascade_virq = cascade_data->get_irq(cascade_data->data);
+	if (cascade_virq)
+		generic_handle_irq(cascade_virq);
+}
+
+void mpc52xx_handle_edge_cascade(unsigned int virq, struct irq_desc *desc)
+{
+	mpc52xx_handle_level_cascade(virq, desc);
+	/** TODO: clear edge IRQ here **/
+}
+
+int mpc52xx_cascade_setup(int virq, int (*get_irq)(void *data), void *data)
+{
+	struct mpc52xx_cascade_data *cascade_data;
+
+	cascade_data = kzalloc(sizeof(struct mpc52xx_cascade_data), GFP_KERNEL);
+	if (!cascade_data)
+		return -ENOMEM;
+
+	/* TODO: make this handle edge cascades too */
+	cascade_data->get_irq = get_irq;
+	cascade_data->data = data;
+	set_irq_data(virq, cascade_data);
+	set_irq_chained_handler(virq, mpc52xx_handle_level_cascade);
+
+	return 0;
+}
+
 static struct irq_host_ops mpc52xx_irqhost_ops = {
 	.xlate = mpc52xx_irqhost_xlate,
 	.map = mpc52xx_irqhost_map,
+	.cascade_setup = mpc52xx_cascade_setup,
 };
 
 /**