MIPS: ath25: add interrupts handling routines

Add interrupts initialization and handling routines, also add AHB bus
error interrupt handlers for both SoCs families.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Cc: Linux MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/8240/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/ath25/ar2315.c

@@ -16,6 +16,9 @@
 
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/bitops.h>
+#include <linux/irqdomain.h>
+#include <linux/interrupt.h>
 #include <linux/reboot.h>
 #include <asm/bootinfo.h>
 #include <asm/reboot.h>
@@ -26,6 +29,7 @@
 #include "ar2315_regs.h"
 
 static void __iomem *ar2315_rst_base;
+static struct irq_domain *ar2315_misc_irq_domain;
 
 static inline u32 ar2315_rst_reg_read(u32 reg)
 {
@@ -46,6 +50,116 @@ static inline void ar2315_rst_reg_mask(u32 reg, u32 mask, u32 val)
 	ar2315_rst_reg_write(reg, ret);
 }
 
+static irqreturn_t ar2315_ahb_err_handler(int cpl, void *dev_id)
+{
+	ar2315_rst_reg_write(AR2315_AHB_ERR0, AR2315_AHB_ERROR_DET);
+	ar2315_rst_reg_read(AR2315_AHB_ERR1);
+
+	pr_emerg("AHB fatal error\n");
+	machine_restart("AHB error"); /* Catastrophic failure */
+
+	return IRQ_HANDLED;
+}
+
+static struct irqaction ar2315_ahb_err_interrupt  = {
+	.handler	= ar2315_ahb_err_handler,
+	.name		= "ar2315-ahb-error",
+};
+
+static void ar2315_misc_irq_handler(unsigned irq, struct irq_desc *desc)
+{
+	u32 pending = ar2315_rst_reg_read(AR2315_ISR) &
+		      ar2315_rst_reg_read(AR2315_IMR);
+	unsigned nr, misc_irq = 0;
+
+	if (pending) {
+		struct irq_domain *domain = irq_get_handler_data(irq);
+
+		nr = __ffs(pending);
+		misc_irq = irq_find_mapping(domain, nr);
+	}
+
+	if (misc_irq) {
+		if (nr == AR2315_MISC_IRQ_GPIO)
+			ar2315_rst_reg_write(AR2315_ISR, AR2315_ISR_GPIO);
+		else if (nr == AR2315_MISC_IRQ_WATCHDOG)
+			ar2315_rst_reg_write(AR2315_ISR, AR2315_ISR_WD);
+		generic_handle_irq(misc_irq);
+	} else {
+		spurious_interrupt();
+	}
+}
+
+static void ar2315_misc_irq_unmask(struct irq_data *d)
+{
+	ar2315_rst_reg_mask(AR2315_IMR, 0, BIT(d->hwirq));
+}
+
+static void ar2315_misc_irq_mask(struct irq_data *d)
+{
+	ar2315_rst_reg_mask(AR2315_IMR, BIT(d->hwirq), 0);
+}
+
+static struct irq_chip ar2315_misc_irq_chip = {
+	.name		= "ar2315-misc",
+	.irq_unmask	= ar2315_misc_irq_unmask,
+	.irq_mask	= ar2315_misc_irq_mask,
+};
+
+static int ar2315_misc_irq_map(struct irq_domain *d, unsigned irq,
+			       irq_hw_number_t hw)
+{
+	irq_set_chip_and_handler(irq, &ar2315_misc_irq_chip, handle_level_irq);
+	return 0;
+}
+
+static struct irq_domain_ops ar2315_misc_irq_domain_ops = {
+	.map = ar2315_misc_irq_map,
+};
+
+/*
+ * Called when an interrupt is received, this function
+ * determines exactly which interrupt it was, and it
+ * invokes the appropriate handler.
+ *
+ * Implicitly, we also define interrupt priority by
+ * choosing which to dispatch first.
+ */
+static void ar2315_irq_dispatch(void)
+{
+	u32 pending = read_c0_status() & read_c0_cause();
+
+	if (pending & CAUSEF_IP3)
+		do_IRQ(AR2315_IRQ_WLAN0);
+	else if (pending & CAUSEF_IP2)
+		do_IRQ(AR2315_IRQ_MISC);
+	else if (pending & CAUSEF_IP7)
+		do_IRQ(ATH25_IRQ_CPU_CLOCK);
+	else
+		spurious_interrupt();
+}
+
+void __init ar2315_arch_init_irq(void)
+{
+	struct irq_domain *domain;
+	unsigned irq;
+
+	ath25_irq_dispatch = ar2315_irq_dispatch;
+
+	domain = irq_domain_add_linear(NULL, AR2315_MISC_IRQ_COUNT,
+				       &ar2315_misc_irq_domain_ops, NULL);
+	if (!domain)
+		panic("Failed to add IRQ domain");
+
+	irq = irq_create_mapping(domain, AR2315_MISC_IRQ_AHB);
+	setup_irq(irq, &ar2315_ahb_err_interrupt);
+
+	irq_set_chained_handler(AR2315_IRQ_MISC, ar2315_misc_irq_handler);
+	irq_set_handler_data(AR2315_IRQ_MISC, domain);
+
+	ar2315_misc_irq_domain = domain;
+}
+
 static void ar2315_restart(char *command)
 {
 	void (*mips_reset_vec)(void) = (void *)0xbfc00000;