irqchip: Add driver for IXP4xx

The IXP4xx (arch/arm/mach-ixp4xx) is an old Intel XScale
platform that has very wide deployment and use.

As part of modernizing the platform, we need to implement a
proper irqchip in the irqchip subsystem.

The IXP4xx irqchip is tightly jotted together with the GPIO
controller, and whereas in the past we would deal with this
complex logic by adding necessarily different code, we can
nowadays modernize it using a hierarchical irqchip.

The actual IXP4 irqchip is a simple active low level IRQ
controller, whereas the GPIO functionality resides in a
different memory area and adds edge trigger support for
the interrupts.

The interrupts from GPIO lines 0..12 are 1:1 mapped to
a fixed set of hardware IRQs on this IRQchip, so we
expect the child GPIO interrupt controller to go in and
allocate descriptors for these interrupts.

For the other interrupts, as we do not yet have DT
support for this platform, we create a linear irqdomain
and then go in and allocate the IRQs that the legacy
boards use. This code will be removed on the DT probe
path when we add DT support to the platform.

We add some translation code for supporting DT
translations for the fwnodes, but we leave most of that
for later.

Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -1691,6 +1691,8 @@ M:	Krzysztof Halasa <khalasa@piap.pl>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
 F:	arch/arm/mach-ixp4xx/
+F:	drivers/irqchip/irq-ixp4xx.c
+F:	include/linux/irqchip/irq-ixp4xx.h
 
 ARM/INTEL RESEARCH IMOTE/STARGATE 2 MACHINE SUPPORT
 M:	Jonathan Cameron <jic23@cam.ac.uk>

drivers/irqchip/Kconfig

@@ -160,6 +160,12 @@ config IMGPDC_IRQ
 	select GENERIC_IRQ_CHIP
 	select IRQ_DOMAIN
 
+config IXP4XX_IRQ
+	bool
+	select IRQ_DOMAIN
+	select GENERIC_IRQ_MULTI_HANDLER
+	select SPARSE_IRQ
+
 config MADERA_IRQ
 	tristate
 

drivers/irqchip/Makefile

@@ -43,6 +43,7 @@ obj-$(CONFIG_ATMEL_AIC5_IRQ)	+= irq-atmel-aic-common.o irq-atmel-aic5.o
 obj-$(CONFIG_I8259)			+= irq-i8259.o
 obj-$(CONFIG_IMGPDC_IRQ)		+= irq-imgpdc.o
 obj-$(CONFIG_IRQ_MIPS_CPU)		+= irq-mips-cpu.o
+obj-$(CONFIG_IXP4XX_IRQ)		+= irq-ixp4xx.o
 obj-$(CONFIG_SIRF_IRQ)			+= irq-sirfsoc.o
 obj-$(CONFIG_JCORE_AIC)			+= irq-jcore-aic.o
 obj-$(CONFIG_RDA_INTC)			+= irq-rda-intc.o

drivers/irqchip/irq-ixp4xx.c

@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * irqchip for the IXP4xx interrupt controller
+ * Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * Based on arch/arm/mach-ixp4xx/common.c
+ * Copyright 2002 (C) Intel Corporation
+ * Copyright 2003-2004 (C) MontaVista, Software, Inc.
+ * Copyright (C) Deepak Saxena <dsaxena@plexity.net>
+ */
+#include <linux/bitops.h>
+#include <linux/gpio/driver.h>
+#include <linux/irq.h>
+#include <linux/io.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/irq-ixp4xx.h>
+#include <linux/irqdomain.h>
+#include <linux/platform_device.h>
+#include <linux/cpu.h>
+
+#include <asm/exception.h>
+#include <asm/mach/irq.h>
+
+#define IXP4XX_ICPR	0x00 /* Interrupt Status */
+#define IXP4XX_ICMR	0x04 /* Interrupt Enable */
+#define IXP4XX_ICLR	0x08 /* Interrupt IRQ/FIQ Select */
+#define IXP4XX_ICIP	0x0C /* IRQ Status */
+#define IXP4XX_ICFP	0x10 /* FIQ Status */
+#define IXP4XX_ICHR	0x14 /* Interrupt Priority */
+#define IXP4XX_ICIH	0x18 /* IRQ Highest Pri Int */
+#define IXP4XX_ICFH	0x1C /* FIQ Highest Pri Int */
+
+/* IXP43x and IXP46x-only */
+#define	IXP4XX_ICPR2	0x20 /* Interrupt Status 2 */
+#define	IXP4XX_ICMR2	0x24 /* Interrupt Enable 2 */
+#define	IXP4XX_ICLR2	0x28 /* Interrupt IRQ/FIQ Select 2 */
+#define IXP4XX_ICIP2	0x2C /* IRQ Status */
+#define IXP4XX_ICFP2	0x30 /* FIQ Status */
+#define IXP4XX_ICEEN	0x34 /* Error High Pri Enable */
+
+/**
+ * struct ixp4xx_irq - state container for the Faraday IRQ controller
+ * @irqbase: IRQ controller memory base in virtual memory
+ * @is_356: if this is an IXP43x, IXP45x or IX46x SoC (with 64 IRQs)
+ * @irqchip: irqchip for this instance
+ * @domain: IRQ domain for this instance
+ */
+struct ixp4xx_irq {
+	void __iomem *irqbase;
+	bool is_356;
+	struct irq_chip irqchip;
+	struct irq_domain *domain;
+};
+
+/* Local static state container */
+static struct ixp4xx_irq ixirq;
+
+/* GPIO Clocks */
+#define IXP4XX_GPIO_CLK_0		14
+#define IXP4XX_GPIO_CLK_1		15
+
+static int ixp4xx_set_irq_type(struct irq_data *d, unsigned int type)
+{
+	/* All are level active high (asserted) here */
+	if (type != IRQ_TYPE_LEVEL_HIGH)
+		return -EINVAL;
+	return 0;
+}
+
+static void ixp4xx_irq_mask(struct irq_data *d)
+{
+	struct ixp4xx_irq *ixi = irq_data_get_irq_chip_data(d);
+	u32 val;
+
+	if (ixi->is_356 && d->hwirq >= 32) {
+		val = __raw_readl(ixi->irqbase + IXP4XX_ICMR2);
+		val &= ~BIT(d->hwirq - 32);
+		__raw_writel(val, ixi->irqbase + IXP4XX_ICMR2);
+	} else {
+		val = __raw_readl(ixi->irqbase + IXP4XX_ICMR);
+		val &= ~BIT(d->hwirq);
+		__raw_writel(val, ixi->irqbase + IXP4XX_ICMR);
+	}
+}
+
+/*
+ * Level triggered interrupts on GPIO lines can only be cleared when the
+ * interrupt condition disappears.
+ */
+static void ixp4xx_irq_unmask(struct irq_data *d)
+{
+	struct ixp4xx_irq *ixi = irq_data_get_irq_chip_data(d);
+	u32 val;
+
+	if (ixi->is_356 && d->hwirq >= 32) {
+		val = __raw_readl(ixi->irqbase + IXP4XX_ICMR2);
+		val |= BIT(d->hwirq - 32);
+		__raw_writel(val, ixi->irqbase + IXP4XX_ICMR2);
+	} else {
+		val = __raw_readl(ixi->irqbase + IXP4XX_ICMR);
+		val |= BIT(d->hwirq);
+		__raw_writel(val, ixi->irqbase + IXP4XX_ICMR);
+	}
+}
+
+asmlinkage void __exception_irq_entry ixp4xx_handle_irq(struct pt_regs *regs)
+{
+	struct ixp4xx_irq *ixi = &ixirq;
+	unsigned long status;
+	int i;
+
+	status = __raw_readl(ixi->irqbase + IXP4XX_ICIP);
+	for_each_set_bit(i, &status, 32)
+		handle_domain_irq(ixi->domain, i, regs);
+
+	/*
+	 * IXP465/IXP435 has an upper IRQ status register
+	 */
+	if (ixi->is_356) {
+		status = __raw_readl(ixi->irqbase + IXP4XX_ICIP2);
+		for_each_set_bit(i, &status, 32)
+			handle_domain_irq(ixi->domain, i + 32, regs);
+	}
+}
+
+static int ixp4xx_irq_domain_translate(struct irq_domain *domain,
+				       struct irq_fwspec *fwspec,
+				       unsigned long *hwirq,
+				       unsigned int *type)
+{
+	/* We support standard DT translation */
+	if (is_of_node(fwspec->fwnode) && fwspec->param_count == 2) {
+		*hwirq = fwspec->param[0];
+		*type = fwspec->param[1];
+		return 0;
+	}
+
+	if (is_fwnode_irqchip(fwspec->fwnode)) {
+		if (fwspec->param_count != 2)
+			return -EINVAL;
+		*hwirq = fwspec->param[0];
+		*type = fwspec->param[1];
+		WARN_ON(*type == IRQ_TYPE_NONE);
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int ixp4xx_irq_domain_alloc(struct irq_domain *d,
+				   unsigned int irq, unsigned int nr_irqs,
+				   void *data)
+{
+	struct ixp4xx_irq *ixi = d->host_data;
+	irq_hw_number_t hwirq;
+	unsigned int type = IRQ_TYPE_NONE;
+	struct irq_fwspec *fwspec = data;
+	int ret;
+	int i;
+
+	ret = ixp4xx_irq_domain_translate(d, fwspec, &hwirq, &type);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < nr_irqs; i++) {
+		/*
+		 * TODO: after converting IXP4xx to only device tree, set
+		 * handle_bad_irq as default handler and assume all consumers
+		 * call .set_type() as this is provided in the second cell in
+		 * the device tree phandle.
+		 */
+		irq_domain_set_info(d,
+				    irq + i,
+				    hwirq + i,
+				    &ixi->irqchip,
+				    ixi,
+				    handle_level_irq,
+				    NULL, NULL);
+		irq_set_probe(irq + i);
+	}
+
+	return 0;
+}
+
+/*
+ * This needs to be a hierarchical irqdomain to work well with the
+ * GPIO irqchip (which is lower in the hierarchy)
+ */
+static const struct irq_domain_ops ixp4xx_irqdomain_ops = {
+	.translate = ixp4xx_irq_domain_translate,
+	.alloc = ixp4xx_irq_domain_alloc,
+	.free = irq_domain_free_irqs_common,
+};
+
+/**
+ * ixp4xx_get_irq_domain() - retrieve the ixp4xx irq domain
+ *
+ * This function will go away when we transition to DT probing.
+ */
+struct irq_domain *ixp4xx_get_irq_domain(void)
+{
+	struct ixp4xx_irq *ixi = &ixirq;
+
+	return ixi->domain;
+}
+EXPORT_SYMBOL_GPL(ixp4xx_get_irq_domain);
+
+/*
+ * This is the Linux IRQ to hwirq mapping table. This goes away when
+ * we have DT support as all IRQ resources are defined in the device
+ * tree. It will register all the IRQs that are not used by the hierarchical
+ * GPIO IRQ chip. The "holes" inbetween these IRQs will be requested by
+ * the GPIO driver using . This is a step-gap solution.
+ */
+struct ixp4xx_irq_chunk {
+	int irq;
+	int hwirq;
+	int nr_irqs;
+};
+
+static const struct ixp4xx_irq_chunk ixp4xx_irq_chunks[] = {
+	{
+		.irq = 16,
+		.hwirq = 0,
+		.nr_irqs = 6,
+	},
+	{
+		.irq = 24,
+		.hwirq = 8,
+		.nr_irqs = 11,
+	},
+	{
+		.irq = 46,
+		.hwirq = 30,
+		.nr_irqs = 2,
+	},
+	/* Only on the 436 variants */
+	{
+		.irq = 48,
+		.hwirq = 32,
+		.nr_irqs = 10,
+	},
+};
+
+/**
+ * ixp4x_irq_setup() - Common setup code for the IXP4xx interrupt controller
+ * @ixi: State container
+ * @irqbase: Virtual memory base for the interrupt controller
+ * @fwnode: Corresponding fwnode abstraction for this controller
+ * @is_356: if this is an IXP43x, IXP45x or IXP46x SoC variant
+ */
+static int ixp4xx_irq_setup(struct ixp4xx_irq *ixi,
+			    void __iomem *irqbase,
+			    struct fwnode_handle *fwnode,
+			    bool is_356)
+{
+	int nr_irqs;
+
+	ixi->irqbase = irqbase;
+	ixi->is_356 = is_356;
+
+	/* Route all sources to IRQ instead of FIQ */
+	__raw_writel(0x0, ixi->irqbase + IXP4XX_ICLR);
+
+	/* Disable all interrupts */
+	__raw_writel(0x0, ixi->irqbase + IXP4XX_ICMR);
+
+	if (is_356) {
+		/* Route upper 32 sources to IRQ instead of FIQ */
+		__raw_writel(0x0, ixi->irqbase + IXP4XX_ICLR2);
+
+		/* Disable upper 32 interrupts */
+		__raw_writel(0x0, ixi->irqbase + IXP4XX_ICMR2);
+
+		nr_irqs = 64;
+	} else {
+		nr_irqs = 32;
+	}
+
+	ixi->irqchip.name = "IXP4xx";
+	ixi->irqchip.irq_mask = ixp4xx_irq_mask;
+	ixi->irqchip.irq_unmask	= ixp4xx_irq_unmask;
+	ixi->irqchip.irq_set_type = ixp4xx_set_irq_type;
+
+	ixi->domain = irq_domain_create_linear(fwnode, nr_irqs,
+					       &ixp4xx_irqdomain_ops,
+					       ixi);
+	if (!ixi->domain) {
+		pr_crit("IXP4XX: can not add primary irqdomain\n");
+		return -ENODEV;
+	}
+
+	set_handle_irq(ixp4xx_handle_irq);
+
+	return 0;
+}
+
+/**
+ * ixp4xx_irq_init() - Function to initialize the irqchip from boardfiles
+ * @irqbase: physical base for the irq controller
+ * @is_356: if this is an IXP43x, IXP45x or IXP46x SoC variant
+ */
+void __init ixp4xx_irq_init(resource_size_t irqbase,
+			    bool is_356)
+{
+	struct ixp4xx_irq *ixi = &ixirq;
+	void __iomem *base;
+	struct fwnode_handle *fwnode;
+	struct irq_fwspec fwspec;
+	int nr_chunks;
+	int ret;
+	int i;
+
+	base = ioremap(irqbase, 0x100);
+	if (!base) {
+		pr_crit("IXP4XX: could not ioremap interrupt controller\n");
+		return;
+	}
+	fwnode = irq_domain_alloc_fwnode(base);
+	if (!fwnode) {
+		pr_crit("IXP4XX: no domain handle\n");
+		return;
+	}
+	ret = ixp4xx_irq_setup(ixi, base, fwnode, is_356);
+	if (ret) {
+		pr_crit("IXP4XX: failed to set up irqchip\n");
+		irq_domain_free_fwnode(fwnode);
+	}
+
+	nr_chunks = ARRAY_SIZE(ixp4xx_irq_chunks);
+	if (!is_356)
+		nr_chunks--;
+
+	/*
+	 * After adding OF support, this is no longer needed: irqs
+	 * will be allocated for the respective fwnodes.
+	 */
+	for (i = 0; i < nr_chunks; i++) {
+		const struct ixp4xx_irq_chunk *chunk = &ixp4xx_irq_chunks[i];
+
+		pr_info("Allocate Linux IRQs %d..%d HW IRQs %d..%d\n",
+			chunk->irq, chunk->irq + chunk->nr_irqs - 1,
+			chunk->hwirq, chunk->hwirq + chunk->nr_irqs - 1);
+		fwspec.fwnode = fwnode;
+		fwspec.param[0] = chunk->hwirq;
+		fwspec.param[1] = IRQ_TYPE_LEVEL_HIGH;
+		fwspec.param_count = 2;
+		ret = __irq_domain_alloc_irqs(ixi->domain,
+					      chunk->irq,
+					      chunk->nr_irqs,
+					      NUMA_NO_NODE,
+					      &fwspec,
+					      false,
+					      NULL);
+		if (ret < 0) {
+			pr_crit("IXP4XX: can not allocate irqs in hierarchy %d\n",
+				ret);
+			return;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(ixp4xx_irq_init);

include/linux/irqchip/irq-ixp4xx.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __IRQ_IXP4XX_H
+#define __IRQ_IXP4XX_H
+
+#include <linux/ioport.h>
+struct irq_domain;
+
+void ixp4xx_irq_init(resource_size_t irqbase,
+		     bool is_356);
+struct irq_domain *ixp4xx_get_irq_domain(void);
+
+#endif /* __IRQ_IXP4XX_H */