irqchip: Add support for Layerscape external interrupt lines

The LS1021A allows inverting the polarity of six interrupt lines
IRQ[0:5] via the scfg_intpcr register, effectively allowing
IRQ_TYPE_LEVEL_LOW and IRQ_TYPE_EDGE_FALLING for those. We just need to
check the type, set the relevant bit in INTPCR accordingly, and fixup
the type argument before calling the GIC's irq_set_type.

In fact, the power-on-reset value of the INTPCR register on the LS1021A
is so that all six lines have their polarity inverted. Hence any
hardware connected to those lines is unusable without this: If the line
is indeed active low, the generic GIC code will reject an irq spec with
IRQ_TYPE_LEVEL_LOW, while if the line is active high, we must obviously
disable the polarity inversion (writing 0 to the relevant bit) before
unmasking the interrupt.

Some other Layerscape SOCs (LS1043A, LS1046A) have a similar feature,
just with a different number of external interrupt lines (and a
different POR value for the INTPCR register). This driver should be
prepared for supporting those by properly filling out the device tree
node. I have the reference manuals for all three boards, but I've only
tested the driver on an LS1021A.

Unfortunately, the Kconfig symbol ARCH_LAYERSCAPE only exists on
arm64, so do as is done for irq-ls-scfg-msi.c: introduce a new symbol
which is set when either ARCH_LAYERSCAPE or SOC_LS1021A is set.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191107122115.6244-3-linux@rasmusvillemoes.dk

drivers/irqchip/Kconfig

@@ -370,6 +370,10 @@ config MVEBU_PIC
 config MVEBU_SEI
         bool
 
+config LS_EXTIRQ
+	def_bool y if SOC_LS1021A || ARCH_LAYERSCAPE
+	select MFD_SYSCON
+
 config LS_SCFG_MSI
 	def_bool y if SOC_LS1021A || ARCH_LAYERSCAPE
 	depends on PCI && PCI_MSI

drivers/irqchip/Makefile

@@ -84,6 +84,7 @@ obj-$(CONFIG_MVEBU_ICU)			+= irq-mvebu-icu.o
 obj-$(CONFIG_MVEBU_ODMI)		+= irq-mvebu-odmi.o
 obj-$(CONFIG_MVEBU_PIC)			+= irq-mvebu-pic.o
 obj-$(CONFIG_MVEBU_SEI)			+= irq-mvebu-sei.o
+obj-$(CONFIG_LS_EXTIRQ)			+= irq-ls-extirq.o
 obj-$(CONFIG_LS_SCFG_MSI)		+= irq-ls-scfg-msi.o
 obj-$(CONFIG_EZNPS_GIC)			+= irq-eznps.o
 obj-$(CONFIG_ARCH_ASPEED)		+= irq-aspeed-vic.o irq-aspeed-i2c-ic.o

drivers/irqchip/irq-ls-extirq.c

+// SPDX-License-Identifier: GPL-2.0
+
+#define pr_fmt(fmt) "irq-ls-extirq: " fmt
+
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/irqdomain.h>
+#include <linux/of.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include <dt-bindings/interrupt-controller/arm-gic.h>
+
+#define MAXIRQ 12
+#define LS1021A_SCFGREVCR 0x200
+
+struct ls_extirq_data {
+	struct regmap		*syscon;
+	u32			intpcr;
+	bool			bit_reverse;
+	u32			nirq;
+	struct irq_fwspec	map[MAXIRQ];
+};
+
+static int
+ls_extirq_set_type(struct irq_data *data, unsigned int type)
+{
+	struct ls_extirq_data *priv = data->chip_data;
+	irq_hw_number_t hwirq = data->hwirq;
+	u32 value, mask;
+
+	if (priv->bit_reverse)
+		mask = 1U << (31 - hwirq);
+	else
+		mask = 1U << hwirq;
+
+	switch (type) {
+	case IRQ_TYPE_LEVEL_LOW:
+		type = IRQ_TYPE_LEVEL_HIGH;
+		value = mask;
+		break;
+	case IRQ_TYPE_EDGE_FALLING:
+		type = IRQ_TYPE_EDGE_RISING;
+		value = mask;
+		break;
+	case IRQ_TYPE_LEVEL_HIGH:
+	case IRQ_TYPE_EDGE_RISING:
+		value = 0;
+		break;
+	default:
+		return -EINVAL;
+	}
+	regmap_update_bits(priv->syscon, priv->intpcr, mask, value);
+
+	return irq_chip_set_type_parent(data, type);
+}
+
+static struct irq_chip ls_extirq_chip = {
+	.name			= "ls-extirq",
+	.irq_mask		= irq_chip_mask_parent,
+	.irq_unmask		= irq_chip_unmask_parent,
+	.irq_eoi		= irq_chip_eoi_parent,
+	.irq_set_type		= ls_extirq_set_type,
+	.irq_retrigger		= irq_chip_retrigger_hierarchy,
+	.irq_set_affinity	= irq_chip_set_affinity_parent,
+	.flags                  = IRQCHIP_SET_TYPE_MASKED,
+};
+
+static int
+ls_extirq_domain_alloc(struct irq_domain *domain, unsigned int virq,
+		       unsigned int nr_irqs, void *arg)
+{
+	struct ls_extirq_data *priv = domain->host_data;
+	struct irq_fwspec *fwspec = arg;
+	irq_hw_number_t hwirq;
+
+	if (fwspec->param_count != 2)
+		return -EINVAL;
+
+	hwirq = fwspec->param[0];
+	if (hwirq >= priv->nirq)
+		return -EINVAL;
+
+	irq_domain_set_hwirq_and_chip(domain, virq, hwirq, &ls_extirq_chip,
+				      priv);
+
+	return irq_domain_alloc_irqs_parent(domain, virq, 1, &priv->map[hwirq]);
+}
+
+static const struct irq_domain_ops extirq_domain_ops = {
+	.xlate		= irq_domain_xlate_twocell,
+	.alloc		= ls_extirq_domain_alloc,
+	.free		= irq_domain_free_irqs_common,
+};
+
+static int
+ls_extirq_parse_map(struct ls_extirq_data *priv, struct device_node *node)
+{
+	const __be32 *map;
+	u32 mapsize;
+	int ret;
+
+	map = of_get_property(node, "interrupt-map", &mapsize);
+	if (!map)
+		return -ENOENT;
+	if (mapsize % sizeof(*map))
+		return -EINVAL;
+	mapsize /= sizeof(*map);
+
+	while (mapsize) {
+		struct device_node *ipar;
+		u32 hwirq, intsize, j;
+
+		if (mapsize < 3)
+			return -EINVAL;
+		hwirq = be32_to_cpup(map);
+		if (hwirq >= MAXIRQ)
+			return -EINVAL;
+		priv->nirq = max(priv->nirq, hwirq + 1);
+
+		ipar = of_find_node_by_phandle(be32_to_cpup(map + 2));
+		map += 3;
+		mapsize -= 3;
+		if (!ipar)
+			return -EINVAL;
+		priv->map[hwirq].fwnode = &ipar->fwnode;
+		ret = of_property_read_u32(ipar, "#interrupt-cells", &intsize);
+		if (ret)
+			return ret;
+
+		if (intsize > mapsize)
+			return -EINVAL;
+
+		priv->map[hwirq].param_count = intsize;
+		for (j = 0; j < intsize; ++j)
+			priv->map[hwirq].param[j] = be32_to_cpup(map++);
+		mapsize -= intsize;
+	}
+	return 0;
+}
+
+static int __init
+ls_extirq_of_init(struct device_node *node, struct device_node *parent)
+{
+
+	struct irq_domain *domain, *parent_domain;
+	struct ls_extirq_data *priv;
+	int ret;
+
+	parent_domain = irq_find_host(parent);
+	if (!parent_domain) {
+		pr_err("Cannot find parent domain\n");
+		return -ENODEV;
+	}
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->syscon = syscon_node_to_regmap(node->parent);
+	if (IS_ERR(priv->syscon)) {
+		ret = PTR_ERR(priv->syscon);
+		pr_err("Failed to lookup parent regmap\n");
+		goto out;
+	}
+	ret = of_property_read_u32(node, "reg", &priv->intpcr);
+	if (ret) {
+		pr_err("Missing INTPCR offset value\n");
+		goto out;
+	}
+
+	ret = ls_extirq_parse_map(priv, node);
+	if (ret)
+		goto out;
+
+	if (of_device_is_compatible(node, "fsl,ls1021a-extirq")) {
+		u32 revcr;
+
+		ret = regmap_read(priv->syscon, LS1021A_SCFGREVCR, &revcr);
+		if (ret)
+			goto out;
+		priv->bit_reverse = (revcr != 0);
+	}
+
+	domain = irq_domain_add_hierarchy(parent_domain, 0, priv->nirq, node,
+					  &extirq_domain_ops, priv);
+	if (!domain)
+		ret = -ENOMEM;
+
+out:
+	if (ret)
+		kfree(priv);
+	return ret;
+}
+
+IRQCHIP_DECLARE(ls1021a_extirq, "fsl,ls1021a-extirq", ls_extirq_of_init);