irqchip/riscv-aplic: Add support for MSI-mode

The RISC-V advanced platform-level interrupt controller (APLIC) has
two modes of operation: 1) Direct mode and 2) MSI mode.
(For more details, refer https://github.com/riscv/riscv-aia)

In APLIC MSI-mode, wired interrupts are forwared as message signaled
interrupts (MSIs) to CPUs via IMSIC.

Extend the existing APLIC irqchip driver to support MSI-mode for
RISC-V platforms having both wired interrupts and MSIs.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20240307140307.646078-8-apatel@ventanamicro.com

drivers/irqchip/Kconfig

@@ -545,6 +545,12 @@ config RISCV_APLIC
 	depends on RISCV
 	select IRQ_DOMAIN_HIERARCHY
 
+config RISCV_APLIC_MSI
+	bool
+	depends on RISCV_APLIC
+	select GENERIC_MSI_IRQ
+	default RISCV_APLIC
+
 config RISCV_IMSIC
 	bool
 	depends on RISCV

drivers/irqchip/Makefile

@@ -96,6 +96,7 @@ 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_APLIC)		+= irq-riscv-aplic-main.o irq-riscv-aplic-direct.o
+obj-$(CONFIG_RISCV_APLIC_MSI)		+= irq-riscv-aplic-msi.o
 obj-$(CONFIG_RISCV_IMSIC)		+= irq-riscv-imsic-state.o irq-riscv-imsic-early.o irq-riscv-imsic-platform.o
 obj-$(CONFIG_SIFIVE_PLIC)		+= irq-sifive-plic.o
 obj-$(CONFIG_STARFIVE_JH8100_INTC)	+= irq-starfive-jh8100-intc.o

drivers/irqchip/irq-riscv-aplic-main.c

@@ -187,7 +187,7 @@ static int aplic_probe(struct platform_device *pdev)
 	if (is_of_node(dev->fwnode))
 		msi_mode = of_property_present(to_of_node(dev->fwnode), "msi-parent");
 	if (msi_mode)
-		rc = -ENODEV;
+		rc = aplic_msi_setup(dev, regs);
 	else
 		rc = aplic_direct_setup(dev, regs);
 	if (rc)

drivers/irqchip/irq-riscv-aplic-main.h

@@ -40,5 +40,13 @@ int aplic_irqdomain_translate(struct irq_fwspec *fwspec, u32 gsi_base,
 void aplic_init_hw_global(struct aplic_priv *priv, bool msi_mode);
 int aplic_setup_priv(struct aplic_priv *priv, struct device *dev, void __iomem *regs);
 int aplic_direct_setup(struct device *dev, void __iomem *regs);
+#ifdef CONFIG_RISCV_APLIC_MSI
+int aplic_msi_setup(struct device *dev, void __iomem *regs);
+#else
+static inline int aplic_msi_setup(struct device *dev, void __iomem *regs)
+{
+	return -ENODEV;
+}
+#endif
 
 #endif

drivers/irqchip/irq-riscv-aplic-msi.c

@@ -0,0 +1,257 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2022 Ventana Micro Systems Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/cpu.h>
+#include <linux/interrupt.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/riscv-aplic.h>
+#include <linux/irqchip/riscv-imsic.h>
+#include <linux/module.h>
+#include <linux/msi.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/smp.h>
+
+#include "irq-riscv-aplic-main.h"
+
+static void aplic_msi_irq_mask(struct irq_data *d)
+{
+	aplic_irq_mask(d);
+	irq_chip_mask_parent(d);
+}
+
+static void aplic_msi_irq_unmask(struct irq_data *d)
+{
+	irq_chip_unmask_parent(d);
+	aplic_irq_unmask(d);
+}
+
+static void aplic_msi_irq_eoi(struct irq_data *d)
+{
+	struct aplic_priv *priv = irq_data_get_irq_chip_data(d);
+
+	/*
+	 * EOI handling is required only for level-triggered interrupts
+	 * when APLIC is in MSI mode.
+	 */
+
+	switch (irqd_get_trigger_type(d)) {
+	case IRQ_TYPE_LEVEL_LOW:
+	case IRQ_TYPE_LEVEL_HIGH:
+		/*
+		 * The section "4.9.2 Special consideration for level-sensitive interrupt
+		 * sources" of the RISC-V AIA specification says:
+		 *
+		 * A second option is for the interrupt service routine to write the
+		 * APLIC’s source identity number for the interrupt to the domain’s
+		 * setipnum register just before exiting. This will cause the interrupt’s
+		 * pending bit to be set to one again if the source is still asserting
+		 * an interrupt, but not if the source is not asserting an interrupt.
+		 */
+		writel(d->hwirq, priv->regs + APLIC_SETIPNUM_LE);
+		break;
+	}
+}
+
+static void aplic_msi_write_msg(struct irq_data *d, struct msi_msg *msg)
+{
+	unsigned int group_index, hart_index, guest_index, val;
+	struct aplic_priv *priv = irq_data_get_irq_chip_data(d);
+	struct aplic_msicfg *mc = &priv->msicfg;
+	phys_addr_t tppn, tbppn, msg_addr;
+	void __iomem *target;
+
+	/* For zeroed MSI, simply write zero into the target register */
+	if (!msg->address_hi && !msg->address_lo && !msg->data) {
+		target = priv->regs + APLIC_TARGET_BASE;
+		target += (d->hwirq - 1) * sizeof(u32);
+		writel(0, target);
+		return;
+	}
+
+	/* Sanity check on message data */
+	WARN_ON(msg->data > APLIC_TARGET_EIID_MASK);
+
+	/* Compute target MSI address */
+	msg_addr = (((u64)msg->address_hi) << 32) | msg->address_lo;
+	tppn = msg_addr >> APLIC_xMSICFGADDR_PPN_SHIFT;
+
+	/* Compute target HART Base PPN */
+	tbppn = tppn;
+	tbppn &= ~APLIC_xMSICFGADDR_PPN_HART(mc->lhxs);
+	tbppn &= ~APLIC_xMSICFGADDR_PPN_LHX(mc->lhxw, mc->lhxs);
+	tbppn &= ~APLIC_xMSICFGADDR_PPN_HHX(mc->hhxw, mc->hhxs);
+	WARN_ON(tbppn != mc->base_ppn);
+
+	/* Compute target group and hart indexes */
+	group_index = (tppn >> APLIC_xMSICFGADDR_PPN_HHX_SHIFT(mc->hhxs)) &
+		     APLIC_xMSICFGADDR_PPN_HHX_MASK(mc->hhxw);
+	hart_index = (tppn >> APLIC_xMSICFGADDR_PPN_LHX_SHIFT(mc->lhxs)) &
+		     APLIC_xMSICFGADDR_PPN_LHX_MASK(mc->lhxw);
+	hart_index |= (group_index << mc->lhxw);
+	WARN_ON(hart_index > APLIC_TARGET_HART_IDX_MASK);
+
+	/* Compute target guest index */
+	guest_index = tppn & APLIC_xMSICFGADDR_PPN_HART(mc->lhxs);
+	WARN_ON(guest_index > APLIC_TARGET_GUEST_IDX_MASK);
+
+	/* Update IRQ TARGET register */
+	target = priv->regs + APLIC_TARGET_BASE;
+	target += (d->hwirq - 1) * sizeof(u32);
+	val = FIELD_PREP(APLIC_TARGET_HART_IDX, hart_index);
+	val |= FIELD_PREP(APLIC_TARGET_GUEST_IDX, guest_index);
+	val |= FIELD_PREP(APLIC_TARGET_EIID, msg->data);
+	writel(val, target);
+}
+
+static void aplic_msi_set_desc(msi_alloc_info_t *arg, struct msi_desc *desc)
+{
+	arg->desc = desc;
+	arg->hwirq = (u32)desc->data.icookie.value;
+}
+
+static int aplic_msi_translate(struct irq_domain *d, struct irq_fwspec *fwspec,
+			       unsigned long *hwirq, unsigned int *type)
+{
+	struct msi_domain_info *info = d->host_data;
+	struct aplic_priv *priv = info->data;
+
+	return aplic_irqdomain_translate(fwspec, priv->gsi_base, hwirq, type);
+}
+
+static const struct msi_domain_template aplic_msi_template = {
+	.chip = {
+		.name			= "APLIC-MSI",
+		.irq_mask		= aplic_msi_irq_mask,
+		.irq_unmask		= aplic_msi_irq_unmask,
+		.irq_set_type		= aplic_irq_set_type,
+		.irq_eoi		= aplic_msi_irq_eoi,
+#ifdef CONFIG_SMP
+		.irq_set_affinity	= irq_chip_set_affinity_parent,
+#endif
+		.irq_write_msi_msg	= aplic_msi_write_msg,
+		.flags			= IRQCHIP_SET_TYPE_MASKED |
+					  IRQCHIP_SKIP_SET_WAKE |
+					  IRQCHIP_MASK_ON_SUSPEND,
+	},
+
+	.ops = {
+		.set_desc		= aplic_msi_set_desc,
+		.msi_translate		= aplic_msi_translate,
+	},
+
+	.info = {
+		.bus_token		= DOMAIN_BUS_WIRED_TO_MSI,
+		.flags			= MSI_FLAG_USE_DEV_FWNODE,
+		.handler		= handle_fasteoi_irq,
+		.handler_name		= "fasteoi",
+	},
+};
+
+int aplic_msi_setup(struct device *dev, void __iomem *regs)
+{
+	const struct imsic_global_config *imsic_global;
+	struct aplic_priv *priv;
+	struct aplic_msicfg *mc;
+	phys_addr_t pa;
+	int rc;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	rc = aplic_setup_priv(priv, dev, regs);
+	if (rc) {
+		dev_err(dev, "failed to create APLIC context\n");
+		return rc;
+	}
+	mc = &priv->msicfg;
+
+	/*
+	 * The APLIC outgoing MSI config registers assume target MSI
+	 * controller to be RISC-V AIA IMSIC controller.
+	 */
+	imsic_global = imsic_get_global_config();
+	if (!imsic_global) {
+		dev_err(dev, "IMSIC global config not found\n");
+		return -ENODEV;
+	}
+
+	/* Find number of guest index bits (LHXS) */
+	mc->lhxs = imsic_global->guest_index_bits;
+	if (APLIC_xMSICFGADDRH_LHXS_MASK < mc->lhxs) {
+		dev_err(dev, "IMSIC guest index bits big for APLIC LHXS\n");
+		return -EINVAL;
+	}
+
+	/* Find number of HART index bits (LHXW) */
+	mc->lhxw = imsic_global->hart_index_bits;
+	if (APLIC_xMSICFGADDRH_LHXW_MASK < mc->lhxw) {
+		dev_err(dev, "IMSIC hart index bits big for APLIC LHXW\n");
+		return -EINVAL;
+	}
+
+	/* Find number of group index bits (HHXW) */
+	mc->hhxw = imsic_global->group_index_bits;
+	if (APLIC_xMSICFGADDRH_HHXW_MASK < mc->hhxw) {
+		dev_err(dev, "IMSIC group index bits big for APLIC HHXW\n");
+		return -EINVAL;
+	}
+
+	/* Find first bit position of group index (HHXS) */
+	mc->hhxs = imsic_global->group_index_shift;
+	if (mc->hhxs < (2 * APLIC_xMSICFGADDR_PPN_SHIFT)) {
+		dev_err(dev, "IMSIC group index shift should be >= %d\n",
+			(2 * APLIC_xMSICFGADDR_PPN_SHIFT));
+		return -EINVAL;
+	}
+	mc->hhxs -= (2 * APLIC_xMSICFGADDR_PPN_SHIFT);
+	if (APLIC_xMSICFGADDRH_HHXS_MASK < mc->hhxs) {
+		dev_err(dev, "IMSIC group index shift big for APLIC HHXS\n");
+		return -EINVAL;
+	}
+
+	/* Compute PPN base */
+	mc->base_ppn = imsic_global->base_addr >> APLIC_xMSICFGADDR_PPN_SHIFT;
+	mc->base_ppn &= ~APLIC_xMSICFGADDR_PPN_HART(mc->lhxs);
+	mc->base_ppn &= ~APLIC_xMSICFGADDR_PPN_LHX(mc->lhxw, mc->lhxs);
+	mc->base_ppn &= ~APLIC_xMSICFGADDR_PPN_HHX(mc->hhxw, mc->hhxs);
+
+	/* Setup global config and interrupt delivery */
+	aplic_init_hw_global(priv, true);
+
+	/* Set the APLIC device MSI domain if not available */
+	if (!dev_get_msi_domain(dev)) {
+		/*
+		 * The device MSI domain for OF devices is only set at the
+		 * time of populating/creating OF device. If the device MSI
+		 * domain is discovered later after the OF device is created
+		 * then we need to set it explicitly before using any platform
+		 * MSI functions.
+		 *
+		 * In case of APLIC device, the parent MSI domain is always
+		 * IMSIC and the IMSIC MSI domains are created later through
+		 * the platform driver probing so we set it explicitly here.
+		 */
+		if (is_of_node(dev->fwnode))
+			of_msi_configure(dev, to_of_node(dev->fwnode));
+	}
+
+	if (!msi_create_device_irq_domain(dev, MSI_DEFAULT_DOMAIN, &aplic_msi_template,
+					  priv->nr_irqs + 1, priv, priv)) {
+		dev_err(dev, "failed to create MSI irq domain\n");
+		return -ENOMEM;
+	}
+
+	/* Advertise the interrupt controller */
+	pa = priv->msicfg.base_ppn << APLIC_xMSICFGADDR_PPN_SHIFT;
+	dev_info(dev, "%d interrupts forwared to MSI base %pa\n", priv->nr_irqs, &pa);
+
+	return 0;
+}