irqchip: Add driver for WPCM450 interrupt controller

The WPCM450 AIC ("Advanced Interrupt Controller") is the interrupt
controller found in the Nuvoton WPCM450 SoC and other Winbond/Nuvoton
SoCs.

The list of registers if based on the AMI vendor kernel and the
Nuvoton W90N745 datasheet.

Although the hardware supports other interrupt modes, the driver only
supports high-level interrupts at the moment, because other modes could
not be tested so far.

Signed-off-by: Jonathan Neuschäfer <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/irqchip/Kconfig

···
 	help
 	  Support MStar Interrupt Controller.
 
+config WPCM450_AIC
+	bool "Nuvoton WPCM450 Advanced Interrupt Controller"
+	depends on ARCH_WPCM450 || COMPILE_TEST
+	help
+	  Support for the interrupt controller in the Nuvoton WPCM450 BMC SoC.
+
 endmenu

drivers/irqchip/Makefile

···
 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

drivers/irqchip/irq-wpcm450-aic.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright 2021 Jonathan Neuschäfer
+
+#include <linux/irqchip.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/printk.h>
+
+#include <asm/exception.h>
+
+#define AIC_SCR(x)	((x)*4)	/* Source control registers */
+#define AIC_GEN		0x84	/* Interrupt group enable control register */
+#define AIC_GRSR	0x88	/* Interrupt group raw status register */
+#define AIC_IRSR	0x100	/* Interrupt raw status register */
+#define AIC_IASR	0x104	/* Interrupt active status register */
+#define AIC_ISR		0x108	/* Interrupt status register */
+#define AIC_IPER	0x10c	/* Interrupt priority encoding register */
+#define AIC_ISNR	0x110	/* Interrupt source number register */
+#define AIC_IMR		0x114	/* Interrupt mask register */
+#define AIC_OISR	0x118	/* Output interrupt status register */
+#define AIC_MECR	0x120	/* Mask enable command register */
+#define AIC_MDCR	0x124	/* Mask disable command register */
+#define AIC_SSCR	0x128	/* Source set command register */
+#define AIC_SCCR	0x12c	/* Source clear command register */
+#define AIC_EOSCR	0x130	/* End of service command register */
+
+#define AIC_SCR_SRCTYPE_LOW_LEVEL	(0 << 6)
+#define AIC_SCR_SRCTYPE_HIGH_LEVEL	(1 << 6)
+#define AIC_SCR_SRCTYPE_NEG_EDGE	(2 << 6)
+#define AIC_SCR_SRCTYPE_POS_EDGE	(3 << 6)
+#define AIC_SCR_PRIORITY(x)		(x)
+#define AIC_SCR_PRIORITY_MASK		0x7
+
+#define AIC_NUM_IRQS		32
+
+struct wpcm450_aic {
+	void __iomem *regs;
+	struct irq_domain *domain;
+};
+
+static struct wpcm450_aic *aic;
+
+static void wpcm450_aic_init_hw(void)
+{
+	int i;
+
+	/* Disable (mask) all interrupts */
+	writel(0xffffffff, aic->regs + AIC_MDCR);
+
+	/*
+	 * Make sure the interrupt controller is ready to serve new interrupts.
+	 * Reading from IPER indicates that the nIRQ signal may be deasserted,
+	 * and writing to EOSCR indicates that interrupt handling has finished.
+	 */
+	readl(aic->regs + AIC_IPER);
+	writel(0, aic->regs + AIC_EOSCR);
+
+	/* Initialize trigger mode and priority of each interrupt source */
+	for (i = 0; i < AIC_NUM_IRQS; i++)
+		writel(AIC_SCR_SRCTYPE_HIGH_LEVEL | AIC_SCR_PRIORITY(7),
+		       aic->regs + AIC_SCR(i));
+}
+
+static void __exception_irq_entry wpcm450_aic_handle_irq(struct pt_regs *regs)
+{
+	int hwirq;
+
+	/* Determine the interrupt source */
+	/* Read IPER to signal that nIRQ can be de-asserted */
+	hwirq = readl(aic->regs + AIC_IPER) / 4;
+
+	handle_domain_irq(aic->domain, hwirq, regs);
+}
+
+static void wpcm450_aic_eoi(struct irq_data *d)
+{
+	/* Signal end-of-service */
+	writel(0, aic->regs + AIC_EOSCR);
+}
+
+static void wpcm450_aic_mask(struct irq_data *d)
+{
+	unsigned int mask = BIT(d->hwirq);
+
+	/* Disable (mask) the interrupt */
+	writel(mask, aic->regs + AIC_MDCR);
+}
+
+static void wpcm450_aic_unmask(struct irq_data *d)
+{
+	unsigned int mask = BIT(d->hwirq);
+
+	/* Enable (unmask) the interrupt */
+	writel(mask, aic->regs + AIC_MECR);
+}
+
+static int wpcm450_aic_set_type(struct irq_data *d, unsigned int flow_type)
+{
+	/*
+	 * The hardware supports high/low level, as well as rising/falling edge
+	 * modes, and the DT binding accommodates for that, but as long as
+	 * other modes than high level mode are not used and can't be tested,
+	 * they are rejected in this driver.
+	 */
+	if ((flow_type & IRQ_TYPE_SENSE_MASK) != IRQ_TYPE_LEVEL_HIGH)
+		return -EINVAL;
+
+	return 0;
+}
+
+static struct irq_chip wpcm450_aic_chip = {
+	.name = "wpcm450-aic",
+	.irq_eoi = wpcm450_aic_eoi,
+	.irq_mask = wpcm450_aic_mask,
+	.irq_unmask = wpcm450_aic_unmask,
+	.irq_set_type = wpcm450_aic_set_type,
+};
+
+static int wpcm450_aic_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hwirq)
+{
+	if (hwirq >= AIC_NUM_IRQS)
+		return -EPERM;
+
+	irq_set_chip_and_handler(irq, &wpcm450_aic_chip, handle_fasteoi_irq);
+	irq_set_chip_data(irq, aic);
+	irq_set_probe(irq);
+
+	return 0;
+}
+
+static const struct irq_domain_ops wpcm450_aic_ops = {
+	.map = wpcm450_aic_map,
+	.xlate = irq_domain_xlate_twocell,
+};
+
+static int __init wpcm450_aic_of_init(struct device_node *node,
+				      struct device_node *parent)
+{
+	if (parent)
+		return -EINVAL;
+
+	aic = kzalloc(sizeof(*aic), GFP_KERNEL);
+	if (!aic)
+		return -ENOMEM;
+
+	aic->regs = of_iomap(node, 0);
+	if (!aic->regs) {
+		pr_err("Failed to map WPCM450 AIC registers\n");
+		return -ENOMEM;
+	}
+
+	wpcm450_aic_init_hw();
+
+	set_handle_irq(wpcm450_aic_handle_irq);
+
+	aic->domain = irq_domain_add_linear(node, AIC_NUM_IRQS, &wpcm450_aic_ops, aic);
+
+	return 0;
+}
+
+IRQCHIP_DECLARE(wpcm450_aic, "nuvoton,wpcm450-aic", wpcm450_aic_of_init);