[RFC 12/14] irq_domain: Add support for base irq and hwirq in legacy mappings

[Grant Likely <grant.likely@secretlab.ca>]

Add support for a legacy mapping where irq = (hwirq - first_hwirq + first_irq)
so that a controller driver can allocate a fixed range of irq_descs and use
a simple calculation to translate back and forth between linux and hw irq
numbers.  This is needed to use an irq_domain with many of the ARM interrupt
controller drivers that manage their own irq_desc allocations.  Ultimately
the goal is to migrate those drivers to use the linear revmap, but doing it
this way allows each driver to be converted separately which makes the
migration path easier.

This patch generalizes the IRQ_DOMAIN_MAP_LEGACY method to use
(first_irq-first_hwirq) as the offset between hwirq and linux irq number,
and adds checks to make sure that the hwirq number does not exceed range
assigned to the controller.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 arch/powerpc/include/asm/irq.h   |    3 -
 arch/powerpc/sysdev/i8259.c      |    2 +-
 arch/powerpc/sysdev/tsi108_pci.c |    2 +-
 include/linux/irqdomain.h        |   20 +++++++++-
 kernel/irq/irqdomain.c           |   78 +++++++++++++++++++++++++-------------
 5 files changed, 73 insertions(+), 32 deletions(-)

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index 728cc30..fe0b09d 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -36,9 +36,6 @@ extern atomic_t ppc_n_lost_interrupts;
 /* Total number of virq in the platform */
 #define NR_IRQS		CONFIG_NR_IRQS
 
-/* Number of irqs reserved for the legacy controller */
-#define NUM_ISA_INTERRUPTS	16
-
 /* Same thing, used by the generic IRQ code */
 #define NR_IRQS_LEGACY		NUM_ISA_INTERRUPTS
 
diff --git a/arch/powerpc/sysdev/i8259.c b/arch/powerpc/sysdev/i8259.c
index c591b31..94fd03d 100644
--- a/arch/powerpc/sysdev/i8259.c
+++ b/arch/powerpc/sysdev/i8259.c
@@ -263,7 +263,7 @@ void i8259_init(struct device_node *node, unsigned long intack_addr)
 	raw_spin_unlock_irqrestore(&i8259_lock, flags);
 
 	/* create a legacy host */
-	i8259_host = irq_domain_add_legacy(node, &i8259_host_ops);
+	i8259_host = irq_domain_add_legacy_isa(node, &i8259_host_ops);
 	if (i8259_host == NULL) {
 		printk(KERN_ERR "i8259: failed to allocate irq host !\n");
 		return;
diff --git a/arch/powerpc/sysdev/tsi108_pci.c b/arch/powerpc/sysdev/tsi108_pci.c
index f2c2c3a..64423a3 100644
--- a/arch/powerpc/sysdev/tsi108_pci.c
+++ b/arch/powerpc/sysdev/tsi108_pci.c
@@ -419,7 +419,7 @@ void __init tsi108_pci_int_init(struct device_node *node)
 {
 	DBG("Tsi108_pci_int_init: initializing PCI interrupts\n");
 
-	pci_irq_host = irq_domain_add_legacy(node, &pci_irq_domain_ops);
+	pci_irq_host = irq_domain_add_legacy_isa(node, &pci_irq_domain_ops);
 	if (pci_irq_host == NULL) {
 		printk(KERN_ERR "pci_irq_host: failed to allocate irq domain!\n");
 		return;
diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index f4325ff..6fb3531 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -95,13 +95,19 @@ struct irq_domain {
 
 	/* type of reverse mapping_technique */
 	unsigned int revmap_type;
-#define IRQ_DOMAIN_MAP_LEGACY 0 /* legacy 8259, gets irqs 1..15 */
+#define IRQ_DOMAIN_MAP_LEGACY 0 /* driver allocated fixed range of irqs.
+				 * ie. legacy 8259, gets irqs 1..15 */
 #define IRQ_DOMAIN_MAP_NOMAP 1 /* no fast reverse mapping */
 #define IRQ_DOMAIN_MAP_LINEAR 2 /* linear map of interrupts */
 #define IRQ_DOMAIN_MAP_TREE 3 /* radix tree */
 	union {
 		struct {
 			unsigned int size;
+			unsigned int first_irq;
+			unsigned int first_hwirq;
+		} legacy;
+		struct {
+			unsigned int size;
 			unsigned int *revmap;
 		} linear;
 		struct radix_tree_root tree;
@@ -121,6 +127,9 @@ struct irq_domain {
 #ifdef CONFIG_IRQ_DOMAIN
 #ifdef CONFIG_PPC
 struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
+					 unsigned int size,
+					 unsigned int first_irq,
+					 unsigned int first_hwirq,
 					 struct irq_domain_ops *ops);
 struct irq_domain *irq_domain_add_linear(struct device_node *of_node,
 					 unsigned int size,
@@ -130,6 +139,15 @@ struct irq_domain *irq_domain_add_nomap(struct device_node *of_node,
 struct irq_domain *irq_domain_add_tree(struct device_node *of_node,
 					 struct irq_domain_ops *ops);
 
+/* Number of irqs reserved for the legacy controller */
+#define NUM_ISA_INTERRUPTS	16
+
+static inline struct irq_domain *irq_domain_add_legacy_isa(
+				struct device_node *of_node,
+				struct irq_domain_ops *ops)
+{
+	return irq_domain_add_legacy(of_node, NUM_ISA_INTERRUPTS-1, 1, 1, ops);
+}
 
 extern struct irq_domain *irq_find_host(struct device_node *node);
 extern void irq_set_default_host(struct irq_domain *host);
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 5959920..d4759d0 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -35,7 +35,7 @@ static struct irq_domain *irq_domain_alloc(struct device_node *of_node,
 					   unsigned int revmap_type,
 					   struct irq_domain_ops *ops)
 {
-	struct irq_domain *domain, *h;
+	struct irq_domain *domain;
 
 	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
 	if (WARN_ON(!domain))
@@ -77,44 +77,65 @@ static struct irq_domain *irq_domain_add(struct device_node *of_node,
  * a legacy controller).
  */
 struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
+					 unsigned int size,
+					 unsigned int first_irq,
+					 unsigned int first_hwirq,
 					 struct irq_domain_ops *ops)
 {
-	struct irq_domain *domain = irq_domain_alloc(of_node, IRQ_DOMAIN_MAP_LEGACY, ops);
+	struct irq_domain *domain;
 	unsigned int i;
 
+	domain = irq_domain_alloc(of_node, IRQ_DOMAIN_MAP_LEGACY, ops);
 	if (!domain)
 		return NULL;
 
 	mutex_lock(&irq_domain_mutex);
-	/* Make sure only one legacy controller can be created */
-	if (revmap_type == IRQ_DOMAIN_MAP_LEGACY) {
-		list_for_each_entry(h, &irq_domain_list, link) {
-			if (WARN_ON(h->revmap_type == IRQ_DOMAIN_MAP_LEGACY)) {
-				mutex_unlock(&irq_domain_mutex);
-				of_node_put(domain->of_node);
-				kfree(domain);
-				return NULL;
-			}
+	/* Verify that all the irqs are available */
+	for (i = 0; i < size; i++) {
+		int irq = first_irq + i;
+		struct irq_data *irq_data = irq_get_irq_data(irq);
+
+		if (WARN_ON(!irq_data || irq_data->domain)) {
+			mutex_unlock(&irq_domain_mutex);
+			of_node_put(domain->of_node);
+			kfree(domain);
+			return NULL;
 		}
 	}
+
+	/* Claim all of the irqs before registering a legacy domain */
+	for (i = 0; i < size; i++) {
+		struct irq_data *irq_data = irq_get_irq_data(first_irq + i);
+		irq_data->hwirq = first_hwirq + i;
+		irq_data->domain = domain;
+	}
+
 	list_add(&domain->link, &irq_domain_list);
 	mutex_unlock(&irq_domain_mutex);
 
-	/* setup us as the domain for all legacy interrupts */
-	for (i = 1; i < NUM_ISA_INTERRUPTS; i++) {
-		struct irq_data *irq_data = irq_get_irq_data(i);
-		irq_data->hwirq = i;
-		irq_data->domain = domain;
+	domain->revmap_data.legacy.first_irq = first_irq;
+	domain->revmap_data.legacy.first_hwirq = first_hwirq;
+	domain->revmap_data.legacy.size = size;
+
+	/* setup initial state for all irqs */
+	for (i = 0; i < size; i++) {
+		int irq = first_irq + i;
+		int hwirq = first_hwirq + i;
 
-		/* Legacy flags are left to default at this point,
-		 * one can then use irq_create_mapping() to
-		 * explicitly change them
+		/* IRQ0 gets ignored */
+		if (!irq)
+			continue;
+
+		/* Legacy flags are left to default at this
+		 * point, one can then use irq_create_mapping()
+		 * to explicitly change them
 		 */
-		ops->map(domain, i, i);
+		ops->map(domain, irq, hwirq);
 
 		/* Clear norequest flags */
-		irq_clear_status_flags(i, IRQ_NOREQUEST);
+		irq_clear_status_flags(irq, IRQ_NOREQUEST);
 	}
+
 	return domain;
 }
 
@@ -313,11 +334,13 @@ unsigned int irq_create_mapping(struct irq_domain *domain,
 
 	/* Get a virtual interrupt number */
 	if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY) {
+		unsigned first_hwirq = domain->revmap_data.legacy.first_hwirq;
+		unsigned first_irq = domain->revmap_data.legacy.first_irq;
+		unsigned size = domain->revmap_data.legacy.size;
 		/* Handle legacy */
-		virq = (unsigned int)hwirq;
-		if (virq == 0 || virq >= NUM_ISA_INTERRUPTS)
+		if (WARN_ON(hwirq < first_hwirq || hwirq >= first_hwirq + size))
 			return 0;
-		return virq;
+		return hwirq - first_hwirq + first_irq;
 	} else {
 		/* Allocate a virtual interrupt number */
 		hint = hwirq % irq_virq_count;
@@ -454,8 +477,11 @@ unsigned int irq_find_mapping(struct irq_domain *domain,
 		return 0;
 
 	/* legacy -> bail early */
-	if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY)
-		return hwirq;
+	if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY) {
+		if (hwirq > domain->revmap_data.legacy.size)
+			return 0;
+		return domain->revmap_data.legacy.first_irq + hwirq;
+	}
 
 	/* Slow path does a linear search of the map */
 	if (hint < NUM_ISA_INTERRUPTS)
-- 
1.7.5.4