ARM: 7389/2: plat-versatile: modernize FPGA IRQ controller

This does two things to the FPGA IRQ controller in the versatile
family:

- Convert to MULTI_IRQ_HANDLER so we can drop the entry macro
  from the Integrator. The C IRQ handler was inspired from
  arch/arm/common/vic.c, recent bug discovered in this handler was
  accounted for.
- Convert to using IRQ domains so we can get rid of the NO_IRQ
  mess and proceed with device tree and such stuff.

As part of the exercise, bump all the low IRQ numbers on the
Integrator PIC to start from 1 rather than 0, since IRQ 0 is
now NO_IRQ. The Linux IRQ numbers are thus entirely decoupled
from the hardware IRQ numbers in this controller.

I was unable to split this patch. The main reason is the half-done
conversion to device tree in Versatile.

Tested on Integrator/AP and Integrator/CP.

Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/plat-versatile/Kconfig

@@ -5,6 +5,12 @@ config PLAT_VERSATILE_CLCD
 
 config PLAT_VERSATILE_FPGA_IRQ
 	bool
+	select IRQ_DOMAIN
+
+config PLAT_VERSATILE_FPGA_IRQ_NR
+       int
+       default 4
+       depends on PLAT_VERSATILE_FPGA_IRQ
 
 config PLAT_VERSATILE_LEDS
 	def_bool y if LEDS_CLASS

arch/arm/plat-versatile/fpga-irq.c

@@ -3,7 +3,10 @@
  */
 #include <linux/irq.h>
 #include <linux/io.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
 
+#include <asm/exception.h>
 #include <asm/mach/irq.h>
 #include <plat/fpga-irq.h>
 
@@ -12,10 +15,32 @@
 #define IRQ_ENABLE_SET		0x08
 #define IRQ_ENABLE_CLEAR	0x0c
 
+/**
+ * struct fpga_irq_data - irq data container for the FPGA IRQ controller
+ * @base: memory offset in virtual memory
+ * @irq_start: first IRQ number handled by this instance
+ * @chip: chip container for this instance
+ * @domain: IRQ domain for this instance
+ * @valid: mask for valid IRQs on this controller
+ * @used_irqs: number of active IRQs on this controller
+ */
+struct fpga_irq_data {
+	void __iomem *base;
+	unsigned int irq_start;
+	struct irq_chip chip;
+	u32 valid;
+	struct irq_domain *domain;
+	u8 used_irqs;
+};
+
+/* we cannot allocate memory when the controllers are initially registered */
+static struct fpga_irq_data fpga_irq_devices[CONFIG_PLAT_VERSATILE_FPGA_IRQ_NR];
+static int fpga_irq_id;
+
 static void fpga_irq_mask(struct irq_data *d)
 {
 	struct fpga_irq_data *f = irq_data_get_irq_chip_data(d);
-	u32 mask = 1 << (d->irq - f->irq_start);
+	u32 mask = 1 << d->hwirq;
 
 	writel(mask, f->base + IRQ_ENABLE_CLEAR);
 }
@@ -23,7 +48,7 @@ static void fpga_irq_mask(struct irq_data *d)
 static void fpga_irq_unmask(struct irq_data *d)
 {
 	struct fpga_irq_data *f = irq_data_get_irq_chip_data(d);
-	u32 mask = 1 << (d->irq - f->irq_start);
+	u32 mask = 1 << d->hwirq;
 
 	writel(mask, f->base + IRQ_ENABLE_SET);
 }
@@ -41,32 +66,93 @@ static void fpga_irq_handle(unsigned int irq, struct irq_desc *desc)
 	do {
 		irq = ffs(status) - 1;
 		status &= ~(1 << irq);
-
-		generic_handle_irq(irq + f->irq_start);
+		generic_handle_irq(irq_find_mapping(f->domain, irq));
 	} while (status);
 }
 
-void __init fpga_irq_init(int parent_irq, u32 valid, struct fpga_irq_data *f)
+/*
+ * Handle each interrupt in a single FPGA IRQ controller.  Returns non-zero
+ * if we've handled at least one interrupt.  This does a single read of the
+ * status register and handles all interrupts in order from LSB first.
+ */
+static int handle_one_fpga(struct fpga_irq_data *f, struct pt_regs *regs)
 {
-	unsigned int i;
+	int handled = 0;
+	int irq;
+	u32 status;
 
+	while ((status  = readl(f->base + IRQ_STATUS))) {
+		irq = ffs(status) - 1;
+		handle_IRQ(irq_find_mapping(f->domain, irq), regs);
+		handled = 1;
+	}
+
+	return handled;
+}
+
+/*
+ * Keep iterating over all registered FPGA IRQ controllers until there are
+ * no pending interrupts.
+ */
+asmlinkage void __exception_irq_entry fpga_handle_irq(struct pt_regs *regs)
+{
+	int i, handled;
+
+	do {
+		for (i = 0, handled = 0; i < fpga_irq_id; ++i)
+			handled |= handle_one_fpga(&fpga_irq_devices[i], regs);
+	} while (handled);
+}
+
+static int fpga_irqdomain_map(struct irq_domain *d, unsigned int irq,
+		irq_hw_number_t hwirq)
+{
+	struct fpga_irq_data *f = d->host_data;
+
+	/* Skip invalid IRQs, only register handlers for the real ones */
+	if (!(f->valid & (1 << hwirq)))
+		return -ENOTSUPP;
+	irq_set_chip_data(irq, f);
+	irq_set_chip_and_handler(irq, &f->chip,
+				handle_level_irq);
+	set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
+	f->used_irqs++;
+	return 0;
+}
+
+static struct irq_domain_ops fpga_irqdomain_ops = {
+	.map = fpga_irqdomain_map,
+	.xlate = irq_domain_xlate_onetwocell,
+};
+
+void __init fpga_irq_init(void __iomem *base, const char *name, int irq_start,
+			  int parent_irq, u32 valid, struct device_node *node)
+{
+	struct fpga_irq_data *f;
+
+	if (fpga_irq_id >= ARRAY_SIZE(fpga_irq_devices)) {
+		printk(KERN_ERR "%s: too few FPGA IRQ controllers, increase CONFIG_PLAT_VERSATILE_FPGA_IRQ_NR\n", __func__);
+		return;
+	}
+
+	f = &fpga_irq_devices[fpga_irq_id];
+	f->base = base;
+	f->irq_start = irq_start;
+	f->chip.name = name;
 	f->chip.irq_ack = fpga_irq_mask;
 	f->chip.irq_mask = fpga_irq_mask;
 	f->chip.irq_unmask = fpga_irq_unmask;
+	f->valid = valid;
 
 	if (parent_irq != -1) {
 		irq_set_handler_data(parent_irq, f);
 		irq_set_chained_handler(parent_irq, fpga_irq_handle);
 	}
 
-	for (i = 0; i < 32; i++) {
-		if (valid & (1 << i)) {
-			unsigned int irq = f->irq_start + i;
+	f->domain = irq_domain_add_legacy(node, fls(valid), f->irq_start, 0,
+					  &fpga_irqdomain_ops, f);
+	pr_info("FPGA IRQ chip %d \"%s\" @ %p, %u irqs\n",
+		fpga_irq_id, name, base, f->used_irqs);
 
-			irq_set_chip_data(irq, f);
-			irq_set_chip_and_handler(irq, &f->chip,
-						 handle_level_irq);
-			set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
-		}
-	}
+	fpga_irq_id++;
 }

arch/arm/plat-versatile/include/plat/fpga-irq.h

@@ -1,12 +1,11 @@
 #ifndef PLAT_FPGA_IRQ_H
 #define PLAT_FPGA_IRQ_H
 
-struct fpga_irq_data {
-	void __iomem *base;
-	unsigned int irq_start;
-	struct irq_chip chip;
-};
+struct device_node;
+struct pt_regs;
 
-void fpga_irq_init(int, u32, struct fpga_irq_data *);
+void fpga_handle_irq(struct pt_regs *regs);
+void fpga_irq_init(void __iomem *, const char *, int, int, u32,
+		struct device_node *node);
 
 #endif