[RFC PATCH v1 05/10] irqchip: Add ACLINT software interrupt driver

[Anup Patel]

The RISC-V ACLINT provides MSWI and SSWI devices for M-mode and
S-mode software interrupts respectively. We add irqchip driver
which provide IPI operations based on ACLINT [M|S]SWI devices
to the Linux RISC-V kernel.

Signed-off-by: Anup Patel <anup.patel at wdc.com>
---
 drivers/irqchip/Kconfig          |  11 +++
 drivers/irqchip/Makefile         |   1 +
 drivers/irqchip/irq-aclint-swi.c | 122 +++++++++++++++++++++++++++++++
 3 files changed, 134 insertions(+)
 create mode 100644 drivers/irqchip/irq-aclint-swi.c

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 62543a4eccc0..2010d493b03b 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -508,6 +508,17 @@ config RISCV_INTC
 
 	   If you don't know what to do here, say Y.
 
+config RISCV_ACLINT_SWI
+	bool "RISC-V Advanced Core Local Interruptor Software Interrupts"
+	depends on RISCV
+	help
+	   This enables support for software interrupts using the Advanced
+	   Core Local Interruptor (ACLINT) found in RISC-V systems.  The
+	   RISC-V ACLINT provides devices for inter-process interrupt and
+	   timer functionality.
+
+	   If you don't know what to do here, say Y.
+
 config SIFIVE_PLIC
 	bool "SiFive Platform-Level Interrupt Controller"
 	depends on RISCV
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index f88cbf36a9d2..a6edf6733c1d 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -97,6 +97,7 @@ obj-$(CONFIG_QCOM_PDC)			+= qcom-pdc.o
 obj-$(CONFIG_CSKY_MPINTC)		+= irq-csky-mpintc.o
 obj-$(CONFIG_CSKY_APB_INTC)		+= irq-csky-apb-intc.o
 obj-$(CONFIG_RISCV_INTC)		+= irq-riscv-intc.o
+obj-$(CONFIG_RISCV_ACLINT_SWI)		+= irq-aclint-swi.o
 obj-$(CONFIG_SIFIVE_PLIC)		+= irq-sifive-plic.o
 obj-$(CONFIG_IMX_IRQSTEER)		+= irq-imx-irqsteer.o
 obj-$(CONFIG_IMX_INTMUX)		+= irq-imx-intmux.o
diff --git a/drivers/irqchip/irq-aclint-swi.c b/drivers/irqchip/irq-aclint-swi.c
new file mode 100644
index 000000000000..f9607072cc7b
--- /dev/null
+++ b/drivers/irqchip/irq-aclint-swi.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ */
+
+#define pr_fmt(fmt) "aclint-swi: " fmt
+#include <linux/cpu.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/smp.h>
+
+struct aclint_swi {
+	void __iomem *sip_reg;
+};
+static DEFINE_PER_CPU(struct aclint_swi, aclint_swis);
+
+static void aclint_swi_send_ipi(const struct cpumask *target)
+{
+	unsigned int cpu;
+	struct aclint_swi *swi;
+
+	for_each_cpu(cpu, target) {
+		swi = per_cpu_ptr(&aclint_swis, cpu);
+		if (!swi->sip_reg) {
+			pr_warn("%s: CPU%d SIP register not available\n",
+				__func__, cpu);
+			continue;
+		}
+
+		writel(1, swi->sip_reg);
+	}
+}
+
+static void aclint_swi_clear_ipi(void)
+{
+	struct aclint_swi *swi = this_cpu_ptr(&aclint_swis);
+
+	if (!swi->sip_reg) {
+		pr_warn("%s: CPU%d SIP register not available\n",
+			__func__, smp_processor_id());
+		return;
+	}
+
+	writel(0, swi->sip_reg);
+}
+
+static struct riscv_ipi_ops aclint_swi_ipi_ops = {
+	.name = "ACLINT-SWI",
+	.use_for_rfence = true,
+	.ipi_inject = aclint_swi_send_ipi,
+	.ipi_clear = aclint_swi_clear_ipi,
+};
+
+static int __init aclint_swi_init(struct device_node *node,
+				  struct device_node *parent)
+{
+	void __iomem *base;
+	struct aclint_swi *swi;
+	u32 i, nr_irqs, nr_cpus = 0;
+
+	/* Map the registers */
+	base = of_iomap(node, 0);
+	if (!base) {
+		pr_err("%pOFP: could not map registers\n", node);
+		return -ENODEV;
+	}
+
+	/* Iterarte over each target CPU connected with this ACLINT */
+	nr_irqs = of_irq_count(node);
+	for (i = 0; i < nr_irqs; i++) {
+		struct of_phandle_args parent;
+		int cpu, hartid;
+
+		if (of_irq_parse_one(node, i, &parent)) {
+			pr_err("%pOFP: failed to parse irq %d.\n",
+			       node, i);
+			continue;
+		}
+
+		if (parent.args[0] != RV_IRQ_SOFT) {
+			pr_err("%pOFP: invalid irq %d (hwirq %d)\n",
+			       node, i, parent.args[0]);
+			continue;
+		}
+
+		hartid = riscv_of_parent_hartid(parent.np);
+		if (hartid < 0) {
+			pr_warn("failed to parse hart ID for irq %d.\n", i);
+			continue;
+		}
+
+		cpu = riscv_hartid_to_cpuid(hartid);
+		if (cpu < 0) {
+			pr_warn("Invalid cpuid for irq %d\n", i);
+			continue;
+		}
+
+		swi = per_cpu_ptr(&aclint_swis, cpu);
+		swi->sip_reg = base + i * sizeof(u32);
+		nr_cpus++;
+	}
+
+	/* Announce the ACLINT SWI device */
+	pr_info("%pOFP: providing IPIs for %d CPUs\n", node, nr_cpus);
+
+	/* Register the IPI operations */
+	riscv_set_ipi_ops(&aclint_swi_ipi_ops);
+
+	return 0;
+}
+
+#ifdef CONFIG_RISCV_M_MODE
+IRQCHIP_DECLARE(riscv_aclint_swi, "riscv,aclint-mswi", aclint_swi_init);
+#else
+IRQCHIP_DECLARE(riscv_aclint_swi, "riscv,aclint-sswi", aclint_swi_init);
+#endif
-- 
2.25.1