[PATCH 2/3] irqchip: al-fic: Introduce Amazon's Annapurna Labs Fabric Interrupt Controller Driver

[Talel Shenhar <talel@amazon.com>]

The Amazon's Annapurna Labs Fabric Interrupt Controller has 32 inputs
lines. A FIC (Fabric Interrupt Controller) may be cascaded into another FIC
or directly to the main CPU Interrupt Controller (e.g. GIC).

This driver introduces support for initialization based on device-tree
compatibility and run-time for dynamically added FICs (e.g. FICs embedded
to PCIe devices).

Signed-off-by: Talel Shenhar <talel@amazon.com>
---
 MAINTAINERS                    |   7 +
 drivers/irqchip/Kconfig        |  11 ++
 drivers/irqchip/Makefile       |   1 +
 drivers/irqchip/irq-al-fic.c   | 346 +++++++++++++++++++++++++++++++++++++++++
 include/linux/irqchip/al-fic.h |  21 +++
 5 files changed, 386 insertions(+)
 create mode 100644 drivers/irqchip/irq-al-fic.c
 create mode 100644 include/linux/irqchip/al-fic.h

diff --git a/MAINTAINERS b/MAINTAINERS
index f485597..c28a97f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1209,6 +1209,13 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/interrupt-controller/arm,vic.txt
 F:	drivers/irqchip/irq-vic.c
 
+AMAZON ANNAPURNA LABS FIC DRIVER
+M:	Talel Shenhar <talel@amazon.com>
+S:	Maintained
+F:	Documentation/devicetree/bindings/interrupt-controller/amazon,al-fic.txt
+F:	drivers/irqchip/irq-al-fic.c
+F:	include/linux/irqchip/al-fic.h
+
 ARM SMMU DRIVERS
 M:	Will Deacon <will.deacon@arm.com>
 R:	Robin Murphy <robin.murphy@arm.com>
diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 51a5ef0..1e51f0f 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -89,6 +89,17 @@ config ALPINE_MSI
 	select PCI_MSI
 	select GENERIC_IRQ_CHIP
 
+config AL_FIC
+	bool "Amazon's Annapurna Labs Fabric Interrupt Controller"
+	depends on OF || COMPILE_TEST
+	select GENERIC_IRQ_CHIP
+	select IRQ_DOMAIN
+	select GENERIC_IRQ_MULTI_HANDLER
+	select IRQ_DOMAIN_HIERARCHY
+	select SPARSE_IRQ
+	help
+	  Support Amazon's Annapurna Labs Fabric Interrupt Controller.
+
 config ATMEL_AIC_IRQ
 	bool
 	select GENERIC_IRQ_CHIP
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index 794c13d..a20eba5 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_IRQCHIP)			+= irqchip.o
 
+obj-$(CONFIG_AL_FIC)			+= irq-al-fic.o
 obj-$(CONFIG_ALPINE_MSI)		+= irq-alpine-msi.o
 obj-$(CONFIG_ATH79)			+= irq-ath79-cpu.o
 obj-$(CONFIG_ATH79)			+= irq-ath79-misc.o
diff --git a/drivers/irqchip/irq-al-fic.c b/drivers/irqchip/irq-al-fic.c
new file mode 100644
index 0000000..d881d42
--- /dev/null
+++ b/drivers/irqchip/irq-al-fic.c
@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0
+/**
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/irqchip/al-fic.h>
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+/* FIC Registers */
+#define AL_FIC_CAUSE		0x00
+#define AL_FIC_MASK		0x10
+#define AL_FIC_CONTROL		0x28
+
+#define CONTROL_TRIGGER_RISING	BIT(3)
+#define CONTROL_MASK_MSI_X	BIT(5)
+
+#define NR_FIC_IRQS 32
+
+MODULE_AUTHOR("Talel Shenhar");
+MODULE_DESCRIPTION("Amazon's Annapurna Labs Interrupt Controller Driver");
+MODULE_LICENSE("GPL v2");
+
+enum al_fic_state {
+	AL_FIC_CLEAN = 0,
+	AL_FIC_CONFIGURED_LEVEL,
+	AL_FIC_CONFIGURED_RAISING_EDGE,
+};
+
+struct al_fic {
+	void __iomem *base;
+	struct irq_domain *domain;
+	const char *name;
+	unsigned int parent_irq;
+	enum al_fic_state state;
+};
+
+static void al_fic_set_trigger(struct al_fic *fic,
+			       struct irq_chip_generic *gc,
+			       enum al_fic_state new_state)
+{
+	irq_flow_handler_t handler;
+	u32 control = readl(fic->base + AL_FIC_CONTROL);
+
+	if (new_state == AL_FIC_CONFIGURED_LEVEL) {
+		handler = handle_level_irq;
+		control &= ~CONTROL_TRIGGER_RISING;
+	} else {
+		handler = handle_edge_irq;
+		control |= CONTROL_TRIGGER_RISING;
+	}
+	gc->chip_types->handler = handler;
+	fic->state = new_state;
+	writel(control, fic->base + AL_FIC_CONTROL);
+}
+
+static int al_fic_irq_set_type(struct irq_data *data, unsigned int flow_type)
+{
+	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(data);
+	struct al_fic *fic = gc->private;
+	enum al_fic_state new_state;
+	int ret = 0;
+
+	irq_gc_lock(gc);
+
+	if (!(flow_type & IRQ_TYPE_LEVEL_HIGH) &&
+	    !(flow_type & IRQ_TYPE_EDGE_RISING)) {
+		pr_err("fic doesn't support flow type %d\n", flow_type);
+		ret = -EPERM;
+		goto err;
+	}
+
+	new_state = (flow_type & IRQ_TYPE_LEVEL_HIGH) ?
+		AL_FIC_CONFIGURED_LEVEL : AL_FIC_CONFIGURED_RAISING_EDGE;
+
+	/* A given FIC instance can be either all level or all edge triggered.
+	 * This is generally fixed depending on what pieces of HW it's wired up
+	 * to.
+	 *
+	 * We configure it based on the sensitivity of the first source
+	 * being setup, and reject any subsequent attempt at configuring it in a
+	 * different way.
+	 */
+	if (fic->state == AL_FIC_CLEAN) {
+		al_fic_set_trigger(fic, gc, new_state);
+	} else if (fic->state != new_state) {
+		pr_err("fic %s state already configured to %d\n",
+		       fic->name, fic->state);
+		ret = -EPERM;
+		goto err;
+	}
+
+err:
+	irq_gc_unlock(gc);
+
+	return ret;
+}
+
+static void al_fic_irq_handler(struct irq_desc *desc)
+{
+	struct al_fic *fic = irq_desc_get_handler_data(desc);
+	struct irq_domain *domain = fic->domain;
+	struct irq_chip *irqchip = irq_desc_get_chip(desc);
+	struct irq_chip_generic *gc = irq_get_domain_generic_chip(domain, 0);
+	unsigned long pending;
+	unsigned int irq;
+	u32 hwirq;
+
+	chained_irq_enter(irqchip, desc);
+
+	pending = readl(fic->base + AL_FIC_CAUSE);
+	pending &= ~gc->mask_cache;
+
+	for_each_set_bit(hwirq, &pending, domain->revmap_size) {
+		irq = irq_find_mapping(domain, hwirq);
+		generic_handle_irq(irq);
+	}
+
+	chained_irq_exit(irqchip, desc);
+}
+
+static int al_fic_register(struct device_node *node,
+			   struct al_fic *fic)
+{
+	struct irq_chip_generic *gc;
+	int ret;
+
+	fic->domain = irq_domain_add_linear(node,
+					    NR_FIC_IRQS,
+					    &irq_generic_chip_ops,
+					    fic);
+	if (!fic->domain) {
+		pr_err("fail to add irq domain\n");
+		return -ENOMEM;
+	}
+
+	ret = irq_alloc_domain_generic_chips(fic->domain,
+					     NR_FIC_IRQS,
+					     1, fic->name,
+					     handle_level_irq,
+					     0, 0, IRQ_GC_INIT_MASK_CACHE);
+	if (ret) {
+		pr_err("fail to allocate generic chip (%d)\n", ret);
+		goto err_domain_remove;
+	}
+
+	gc = irq_get_domain_generic_chip(fic->domain, 0);
+	gc->reg_base = fic->base;
+	gc->chip_types->regs.mask = AL_FIC_MASK;
+	gc->chip_types->regs.ack = AL_FIC_CAUSE;
+	gc->chip_types->chip.irq_mask = irq_gc_mask_set_bit;
+	gc->chip_types->chip.irq_unmask = irq_gc_mask_clr_bit;
+	gc->chip_types->chip.irq_ack = irq_gc_ack_clr_bit;
+	gc->chip_types->chip.irq_set_type = al_fic_irq_set_type;
+	gc->chip_types->chip.flags = IRQCHIP_SKIP_SET_WAKE;
+	gc->private = fic;
+
+	irq_set_chained_handler_and_data(fic->parent_irq,
+					 al_fic_irq_handler,
+					 fic);
+	return 0;
+
+err_domain_remove:
+	irq_domain_remove(fic->domain);
+
+	return ret;
+}
+
+/**
+ * al_fic_wire_get_domain() - returns the irq_domain assigned to this fic
+ * @fic: fic context configured to Legacy mode
+ *
+ * A fic configured to Legacy mode requires domain to map the hwirqs to virtual
+ * irqs. This API supplies the domain allocated to this fic.
+ *
+ * Returns the irq_domain or ERR_PTR on error.
+ */
+struct irq_domain *al_fic_wire_get_domain(struct al_fic *fic)
+{
+	if (!fic)
+		return ERR_PTR(-EINVAL);
+	if (!fic->domain)
+		return ERR_PTR(-EPERM);
+
+	return fic->domain;
+}
+EXPORT_SYMBOL_GPL(al_fic_wire_get_domain);
+
+static void al_fic_hw_init(struct al_fic *fic)
+{
+	u32 control = CONTROL_MASK_MSI_X;
+
+	/* mask out all interrupts */
+	writel(0xFFFFFFFF, fic->base + AL_FIC_MASK);
+
+	/* clear any pending interrupt */
+	writel(0, fic->base + AL_FIC_CAUSE);
+
+	writel(control, fic->base + AL_FIC_CONTROL);
+}
+
+/**
+ * al_fic_wire_init() - initialize and configure fic in wire mode
+ * @of_node: optional pointer to interrupt controller's device tree node.
+ * @base: mmio to fic register
+ * @name: name of the fic
+ * @parent_irq: interrupt of parent
+ *
+ * This API will configure the fic hardware to to work in wire mode.
+ * In wire mode, fic hardware is generating a wire ("wired") interrupt.
+ * Interrupt can be generated based on positive edge or level - configuration is
+ * to be determined based on connected hardware to this fic.
+ *
+ * Returns fic context that allows the user to obtain the irq_domain by using
+ * al_fic_wire_get_domain().
+ */
+struct al_fic *al_fic_wire_init(struct device_node *node,
+				void __iomem *base,
+				const char *name,
+				unsigned int parent_irq)
+{
+	struct al_fic *fic;
+	int ret;
+
+	if (!base)
+		return ERR_PTR(-EINVAL);
+
+	fic = kzalloc(sizeof(*fic), GFP_KERNEL);
+	if (!fic)
+		return ERR_PTR(-ENOMEM);
+
+	fic->base = base;
+	fic->parent_irq = parent_irq;
+	fic->name = (name ?: "al-fic-wire");
+
+	al_fic_hw_init(fic);
+
+	ret = al_fic_register(node, fic);
+	if (ret) {
+		pr_err("fail to register irqchip\n");
+		goto err_free;
+	}
+
+	pr_debug("%s initialized successfully in Legacy mode (parent-irq=%u)\n",
+		 fic->name, parent_irq);
+
+	return fic;
+
+err_free:
+	kfree(fic);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(al_fic_wire_init);
+
+/**
+ * al_fic_cleanup() - free all resources allocated by fic
+ * @fic: pointer to fic context
+ *
+ * This API will release the domain (in case of wire mode) and will free the
+ * context allocated for this fic.
+ * Caller should call this API only after all interrupts were released.
+ *
+ * Returns 0 on success or negative error code.
+ */
+int al_fic_cleanup(struct al_fic *fic)
+{
+	if (!fic)
+		return -EINVAL;
+
+	if (fic->domain) {
+		struct irq_chip_generic *gc;
+
+		gc = irq_get_domain_generic_chip(fic->domain, 0);
+		if (IS_ERR(gc)) {
+			pr_err("%s was not able to grab gc for fic (%lu)\n",
+			       __func__, PTR_ERR(gc));
+			return PTR_ERR(gc);
+		}
+
+		irq_destroy_generic_chip(gc, 0, 0, 0);
+		irq_domain_remove(fic->domain);
+	}
+
+	kfree(fic);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(al_fic_cleanup);
+
+static int __init al_fic_init_dt(struct device_node *node,
+				 struct device_node *parent)
+{
+	int ret;
+	void __iomem *base;
+	unsigned int parent_irq;
+	struct al_fic *fic;
+
+	if (!parent) {
+		pr_err("%s: unsupported - device require a parent\n",
+		       node->name);
+		return -EINVAL;
+	}
+
+	base = of_iomap(node, 0);
+	if (!base) {
+		pr_err("%s: fail to map memory\n", node->name);
+		return -ENOMEM;
+	}
+
+	parent_irq = irq_of_parse_and_map(node, 0);
+	if (!parent_irq) {
+		pr_err("%s: fail to map irq\n", node->name);
+		ret = -EINVAL;
+		goto err_unmap;
+	}
+
+	fic = al_fic_wire_init(node,
+			       base,
+			       node->name,
+			       parent_irq);
+	if (IS_ERR(fic)) {
+		pr_err("%s: fail to initialize irqchip (%lu)\n",
+		       node->name,
+		       PTR_ERR(fic));
+		ret = PTR_ERR(fic);
+		goto err_irq_dispose;
+	}
+
+	return 0;
+
+err_irq_dispose:
+	irq_dispose_mapping(parent_irq);
+err_unmap:
+	iounmap(base);
+
+	return ret;
+}
+
+IRQCHIP_DECLARE(al_fic, "amazon,al-fic", al_fic_init_dt);
diff --git a/include/linux/irqchip/al-fic.h b/include/linux/irqchip/al-fic.h
new file mode 100644
index 0000000..0833749
--- /dev/null
+++ b/include/linux/irqchip/al-fic.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/**
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ */
+
+#ifndef _AL_FIC_H_
+#define _AL_FIC_H_
+
+#include <linux/irqdomain.h>
+
+struct al_fic;
+
+struct irq_domain *al_fic_wire_get_domain(struct al_fic *fic);
+
+struct al_fic *al_fic_wire_init(struct device_node *node,
+				void __iomem *base,
+				const char *name,
+				unsigned int parent_irq);
+int al_fic_cleanup(struct al_fic *fic);
+
+#endif
-- 
2.7.4