powerpc/xics: Add a native ICS backend for microwatt

This is a simple native ICS backend that matches the layout of
the Microwatt implementation of ICS.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
[mpe: Add empty ics_native_init() to unbreak non-microwatt builds]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

fixup-ics
Link: https://lore.kernel.org/r/YMwW8cxrwB2W5EUN@thinks.paulus.ozlabs.org

arch/powerpc/boot/dts/microwatt.dts

@@ -99,7 +99,25 @@ soc@c0000000 {
 		compatible = "simple-bus";
 		#address-cells = <1>;
 		#size-cells = <1>;
+		interrupt-parent = <&ICS>;
 
 		ranges = <0 0 0xc0000000 0x40000000>;
+
+		interrupt-controller@4000 {
+			compatible = "openpower,xics-presentation", "ibm,ppc-xicp";
+			ibm,interrupt-server-ranges = <0x0 0x1>;
+			reg = <0x4000 0x100>;
+		};
+
+		ICS: interrupt-controller@5000 {
+			compatible = "openpower,xics-sources";
+			interrupt-controller;
+			interrupt-ranges = <0x10 0x10>;
+			reg = <0x5000 0x100>;
+			#address-cells = <0>;
+			#size-cells = <0>;
+			#interrupt-cells = <2>;
+		};
+
 	};
 };

arch/powerpc/include/asm/xics.h

@@ -65,8 +65,12 @@ struct icp_ops {
 
 extern const struct icp_ops *icp_ops;
 
+#ifdef CONFIG_PPC_ICS_NATIVE
 /* Native ICS */
 extern int ics_native_init(void);
+#else
+static inline int ics_native_init(void) { return -ENODEV; }
+#endif
 
 /* RTAS ICS */
 #ifdef CONFIG_PPC_ICS_RTAS

arch/powerpc/platforms/microwatt/Kconfig

@@ -3,6 +3,8 @@ config PPC_MICROWATT
 	depends on PPC_BOOK3S_64 && !SMP
 	bool "Microwatt SoC platform"
 	select PPC_XICS
+	select PPC_ICS_NATIVE
+	select PPC_ICP_NATIVE
 	select PPC_NATIVE
 	help
           This option enables support for FPGA-based Microwatt implementations.

arch/powerpc/platforms/microwatt/setup.c

@@ -10,8 +10,15 @@
 #include <linux/init.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
+
 #include <asm/machdep.h>
 #include <asm/time.h>
+#include <asm/xics.h>
+
+static void __init microwatt_init_IRQ(void)
+{
+	xics_init();
+}
 
 static int __init microwatt_probe(void)
 {
@@ -27,5 +34,6 @@ machine_arch_initcall(microwatt, microwatt_populate);
 define_machine(microwatt) {
 	.name			= "microwatt",
 	.probe			= microwatt_probe,
+	.init_IRQ		= microwatt_init_IRQ,
 	.calibrate_decr		= generic_calibrate_decr,
 };

arch/powerpc/sysdev/xics/Kconfig

@@ -12,3 +12,6 @@ config PPC_ICP_HV
 
 config PPC_ICS_RTAS
 	def_bool n
+
+config PPC_ICS_NATIVE
+	def_bool n

arch/powerpc/sysdev/xics/Makefile

@@ -4,4 +4,5 @@ obj-y				+= xics-common.o
 obj-$(CONFIG_PPC_ICP_NATIVE)	+= icp-native.o
 obj-$(CONFIG_PPC_ICP_HV)	+= icp-hv.o
 obj-$(CONFIG_PPC_ICS_RTAS)	+= ics-rtas.o
+obj-$(CONFIG_PPC_ICS_NATIVE)	+= ics-native.o
 obj-$(CONFIG_PPC_POWERNV)	+= ics-opal.o icp-opal.o

arch/powerpc/sysdev/xics/ics-native.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * ICS backend for OPAL managed interrupts.
+ *
+ * Copyright 2011 IBM Corp.
+ */
+
+//#define DEBUG
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/irq.h>
+#include <linux/smp.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/cpu.h>
+#include <linux/of.h>
+#include <linux/spinlock.h>
+#include <linux/msi.h>
+#include <linux/list.h>
+
+#include <asm/prom.h>
+#include <asm/smp.h>
+#include <asm/machdep.h>
+#include <asm/irq.h>
+#include <asm/errno.h>
+#include <asm/xics.h>
+#include <asm/opal.h>
+#include <asm/firmware.h>
+
+struct ics_native {
+	struct ics		ics;
+	struct device_node	*node;
+	void __iomem    	*base;
+	u32             	ibase;
+	u32             	icount;
+};
+#define to_ics_native(_ics)     container_of(_ics, struct ics_native, ics)
+
+static void __iomem *ics_native_xive(struct ics_native *in, unsigned int vec)
+{
+	return in->base + 0x800 + ((vec - in->ibase) << 2);
+}
+
+static void ics_native_unmask_irq(struct irq_data *d)
+{
+	unsigned int vec = (unsigned int)irqd_to_hwirq(d);
+	struct ics *ics = irq_data_get_irq_chip_data(d);
+	struct ics_native *in = to_ics_native(ics);
+	unsigned int server;
+
+	pr_devel("ics-native: unmask virq %d [hw 0x%x]\n", d->irq, vec);
+
+	if (vec < in->ibase || vec >= (in->ibase + in->icount))
+		return;
+
+	server = xics_get_irq_server(d->irq, irq_data_get_affinity_mask(d), 0);
+	out_be32(ics_native_xive(in, vec), (server << 8) | DEFAULT_PRIORITY);
+}
+
+static unsigned int ics_native_startup(struct irq_data *d)
+{
+#ifdef CONFIG_PCI_MSI
+	/*
+	 * The generic MSI code returns with the interrupt disabled on the
+	 * card, using the MSI mask bits. Firmware doesn't appear to unmask
+	 * at that level, so we do it here by hand.
+	 */
+	if (irq_data_get_msi_desc(d))
+		pci_msi_unmask_irq(d);
+#endif
+
+	/* unmask it */
+	ics_native_unmask_irq(d);
+	return 0;
+}
+
+static void ics_native_do_mask(struct ics_native *in, unsigned int vec)
+{
+	out_be32(ics_native_xive(in, vec), 0xff);
+}
+
+static void ics_native_mask_irq(struct irq_data *d)
+{
+	unsigned int vec = (unsigned int)irqd_to_hwirq(d);
+	struct ics *ics = irq_data_get_irq_chip_data(d);
+	struct ics_native *in = to_ics_native(ics);
+
+	pr_devel("ics-native: mask virq %d [hw 0x%x]\n", d->irq, vec);
+
+	if (vec < in->ibase || vec >= (in->ibase + in->icount))
+		return;
+	ics_native_do_mask(in, vec);
+}
+
+static int ics_native_set_affinity(struct irq_data *d,
+				   const struct cpumask *cpumask,
+				   bool force)
+{
+	unsigned int vec = (unsigned int)irqd_to_hwirq(d);
+	struct ics *ics = irq_data_get_irq_chip_data(d);
+	struct ics_native *in = to_ics_native(ics);
+	int server;
+	u32 xive;
+
+	if (vec < in->ibase || vec >= (in->ibase + in->icount))
+		return -EINVAL;
+
+	server = xics_get_irq_server(d->irq, cpumask, 1);
+	if (server == -1) {
+		pr_warn("%s: No online cpus in the mask %*pb for irq %d\n",
+			__func__, cpumask_pr_args(cpumask), d->irq);
+		return -1;
+	}
+
+	xive = in_be32(ics_native_xive(in, vec));
+	xive = (xive & 0xff) | (server << 8);
+	out_be32(ics_native_xive(in, vec), xive);
+
+	return IRQ_SET_MASK_OK;
+}
+
+static struct irq_chip ics_native_irq_chip = {
+	.name = "ICS",
+	.irq_startup		= ics_native_startup,
+	.irq_mask		= ics_native_mask_irq,
+	.irq_unmask		= ics_native_unmask_irq,
+	.irq_eoi		= NULL, /* Patched at init time */
+	.irq_set_affinity 	= ics_native_set_affinity,
+	.irq_set_type		= xics_set_irq_type,
+	.irq_retrigger		= xics_retrigger,
+};
+
+static int ics_native_map(struct ics *ics, unsigned int virq)
+{
+	unsigned int vec = (unsigned int)virq_to_hw(virq);
+	struct ics_native *in = to_ics_native(ics);
+
+	pr_devel("%s: vec=0x%x\n", __func__, vec);
+
+	if (vec < in->ibase || vec >= (in->ibase + in->icount))
+		return -EINVAL;
+
+	irq_set_chip_and_handler(virq, &ics_native_irq_chip, handle_fasteoi_irq);
+	irq_set_chip_data(virq, ics);
+
+	return 0;
+}
+
+static void ics_native_mask_unknown(struct ics *ics, unsigned long vec)
+{
+	struct ics_native *in = to_ics_native(ics);
+
+	if (vec < in->ibase || vec >= (in->ibase + in->icount))
+		return;
+
+	ics_native_do_mask(in, vec);
+}
+
+static long ics_native_get_server(struct ics *ics, unsigned long vec)
+{
+	struct ics_native *in = to_ics_native(ics);
+	u32 xive;
+
+	if (vec < in->ibase || vec >= (in->ibase + in->icount))
+		return -EINVAL;
+
+	xive = in_be32(ics_native_xive(in, vec));
+	return (xive >> 8) & 0xfff;
+}
+
+static int ics_native_host_match(struct ics *ics, struct device_node *node)
+{
+	struct ics_native *in = to_ics_native(ics);
+
+	return in->node == node;
+}
+
+static struct ics ics_native_template = {
+	.map		= ics_native_map,
+	.mask_unknown	= ics_native_mask_unknown,
+	.get_server	= ics_native_get_server,
+	.host_match	= ics_native_host_match,
+};
+
+static int __init ics_native_add_one(struct device_node *np)
+{
+	struct ics_native *ics;
+	u32 ranges[2];
+	int rc, count;
+
+	ics = kzalloc(sizeof(struct ics_native), GFP_KERNEL);
+	if (!ics)
+		return -ENOMEM;
+	ics->node = of_node_get(np);
+	memcpy(&ics->ics, &ics_native_template, sizeof(struct ics));
+
+	ics->base = of_iomap(np, 0);
+	if (!ics->base) {
+		pr_err("Failed to map %pOFP\n", np);
+		rc = -ENOMEM;
+		goto fail;
+	}
+
+	count = of_property_count_u32_elems(np, "interrupt-ranges");
+	if (count < 2 || count & 1) {
+		pr_err("Failed to read interrupt-ranges of %pOFP\n", np);
+		rc = -EINVAL;
+		goto fail;
+	}
+	if (count > 2) {
+		pr_warn("ICS %pOFP has %d ranges, only one supported\n",
+			np, count >> 1);
+	}
+	rc = of_property_read_u32_array(np, "interrupt-ranges",
+					ranges, 2);
+	if (rc) {
+		pr_err("Failed to read interrupt-ranges of %pOFP\n", np);
+		goto fail;
+	}
+	ics->ibase = ranges[0];
+	ics->icount = ranges[1];
+
+	pr_info("ICS native initialized for sources %d..%d\n",
+		ics->ibase, ics->ibase + ics->icount - 1);
+
+	/* Register ourselves */
+	xics_register_ics(&ics->ics);
+
+	return 0;
+fail:
+	of_node_put(ics->node);
+	kfree(ics);
+	return rc;
+}
+
+int __init ics_native_init(void)
+{
+	struct device_node *ics;
+	bool found_one = false;
+
+	/* We need to patch our irq chip's EOI to point to the
+	 * right ICP
+	 */
+	ics_native_irq_chip.irq_eoi = icp_ops->eoi;
+
+	/* Find native ICS in the device-tree */
+	for_each_compatible_node(ics, NULL, "openpower,xics-sources") {
+		if (ics_native_add_one(ics) == 0)
+			found_one = true;
+	}
+
+	if (found_one)
+		pr_info("ICS native backend registered\n");
+
+	return found_one ? 0 : -ENODEV;
+}

arch/powerpc/sysdev/xics/xics-common.c

@@ -476,6 +476,8 @@ void __init xics_init(void)
 	rc = ics_rtas_init();
 	if (rc < 0)
 		rc = ics_opal_init();
+	if (rc < 0)
+		rc = ics_native_init();
 	if (rc < 0)
 		pr_warn("XICS: Cannot find a Source Controller !\n");