irqchip: Add support for IDT 79rc3243x interrupt controller

IDT 79rc3243x SoCs have rather simple interrupt controllers connected
to the MIPS CPU interrupt lines. Each of them has room for up to
32 interrupts.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210422145330.73452-1-tsbogend@alpha.franken.de

drivers/irqchip/Kconfig

@@ -583,4 +583,9 @@ config WPCM450_AIC
 	help
 	  Support for the interrupt controller in the Nuvoton WPCM450 BMC SoC.
 
+config IRQ_IDT3243X
+	bool
+	select GENERIC_IRQ_CHIP
+	select IRQ_DOMAIN
+
 endmenu

drivers/irqchip/Makefile

@@ -114,3 +114,4 @@ obj-$(CONFIG_MST_IRQ)			+= irq-mst-intc.o
 obj-$(CONFIG_SL28CPLD_INTC)		+= irq-sl28cpld.o
 obj-$(CONFIG_MACH_REALTEK_RTL)		+= irq-realtek-rtl.o
 obj-$(CONFIG_WPCM450_AIC)		+= irq-wpcm450-aic.o
+obj-$(CONFIG_IRQ_IDT3243X)		+= irq-idt3243x.o

drivers/irqchip/irq-idt3243x.c

@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for IDT/Renesas 79RC3243x Interrupt Controller.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqdomain.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+#define IDT_PIC_NR_IRQS		32
+
+#define IDT_PIC_IRQ_PEND		0x00
+#define IDT_PIC_IRQ_MASK		0x08
+
+struct idt_pic_data {
+	void __iomem *base;
+	struct irq_domain *irq_domain;
+	struct irq_chip_generic *gc;
+};
+
+static void idt_irq_dispatch(struct irq_desc *desc)
+{
+	struct idt_pic_data *idtpic = irq_desc_get_handler_data(desc);
+	struct irq_chip *host_chip = irq_desc_get_chip(desc);
+	u32 pending, hwirq, virq;
+
+	chained_irq_enter(host_chip, desc);
+
+	pending = irq_reg_readl(idtpic->gc, IDT_PIC_IRQ_PEND);
+	pending &= ~idtpic->gc->mask_cache;
+	while (pending) {
+		hwirq = __fls(pending);
+		virq = irq_linear_revmap(idtpic->irq_domain, hwirq);
+		if (virq)
+			generic_handle_irq(virq);
+		pending &= ~(1 << hwirq);
+	}
+
+	chained_irq_exit(host_chip, desc);
+}
+
+static int idt_pic_init(struct device_node *of_node, struct device_node *parent)
+{
+	struct irq_domain *domain;
+	struct idt_pic_data *idtpic;
+	struct irq_chip_generic *gc;
+	struct irq_chip_type *ct;
+	unsigned int parent_irq;
+	int ret = 0;
+
+	idtpic = kzalloc(sizeof(*idtpic), GFP_KERNEL);
+	if (!idtpic) {
+		ret = -ENOMEM;
+		goto out_err;
+	}
+
+	parent_irq = irq_of_parse_and_map(of_node, 0);
+	if (!parent_irq) {
+		pr_err("Failed to map parent IRQ!\n");
+		ret = -EINVAL;
+		goto out_free;
+	}
+
+	idtpic->base = of_iomap(of_node, 0);
+	if (!idtpic->base) {
+		pr_err("Failed to map base address!\n");
+		ret = -ENOMEM;
+		goto out_unmap_irq;
+	}
+
+	domain = irq_domain_add_linear(of_node, IDT_PIC_NR_IRQS,
+				       &irq_generic_chip_ops, NULL);
+	if (!domain) {
+		pr_err("Failed to add irqdomain!\n");
+		ret = -ENOMEM;
+		goto out_iounmap;
+	}
+	idtpic->irq_domain = domain;
+
+	ret = irq_alloc_domain_generic_chips(domain, 32, 1, "IDTPIC",
+					     handle_level_irq, 0,
+					     IRQ_NOPROBE | IRQ_LEVEL, 0);
+	if (ret)
+		goto out_domain_remove;
+
+	gc = irq_get_domain_generic_chip(domain, 0);
+	gc->reg_base = idtpic->base;
+	gc->private = idtpic;
+
+	ct = gc->chip_types;
+	ct->regs.mask = IDT_PIC_IRQ_MASK;
+	ct->chip.irq_mask = irq_gc_mask_set_bit;
+	ct->chip.irq_unmask = irq_gc_mask_clr_bit;
+	idtpic->gc = gc;
+
+	/* Mask interrupts. */
+	writel(0xffffffff, idtpic->base + IDT_PIC_IRQ_MASK);
+	gc->mask_cache = 0xffffffff;
+
+	irq_set_chained_handler_and_data(parent_irq,
+					 idt_irq_dispatch, idtpic);
+
+	return 0;
+
+out_domain_remove:
+	irq_domain_remove(domain);
+out_iounmap:
+	iounmap(idtpic->base);
+out_unmap_irq:
+	irq_dispose_mapping(parent_irq);
+out_free:
+	kfree(idtpic);
+out_err:
+	pr_err("Failed to initialize! (errno = %d)\n", ret);
+	return ret;
+}
+
+IRQCHIP_DECLARE(idt_pic, "idt,32434-pic", idt_pic_init);