iommu/riscv: Add RISC-V IOMMU PCIe device driver

Introduce device driver for PCIe implementation
of RISC-V IOMMU architected hardware.

IOMMU hardware and system support for MSI or MSI-X is
required by this implementation.

Vendor and device identifiers used in this patch
matches QEMU implementation of the RISC-V IOMMU PCIe
device, from Rivos VID (0x1efd) range allocated by the PCI-SIG.

MAINTAINERS | added iommu-pci.c already covered by matching pattern.

Link: https://lore.kernel.org/qemu-devel/20240307160319.675044-1-dbarboza@ventanamicro.com/
Co-developed-by: Nick Kossifidis <mick@ics.forth.gr>
Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/12f3bdbe519ebb7ca482191e7334d38b25b8ae8f.1729059707.git.tjeznach@rivosinc.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/riscv/Kconfig

@@ -13,3 +13,8 @@ config RISCV_IOMMU
 
 	  Say Y here if your SoC includes an IOMMU device implementing
 	  the RISC-V IOMMU architecture.
+
+config RISCV_IOMMU_PCI
+	def_bool y if RISCV_IOMMU && PCI_MSI
+	help
+	  Support for the PCIe implementation of RISC-V IOMMU architecture.

drivers/iommu/riscv/Makefile

@@ -1,2 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_RISCV_IOMMU) += iommu.o iommu-platform.o
+obj-$(CONFIG_RISCV_IOMMU_PCI) += iommu-pci.o

drivers/iommu/riscv/iommu-pci.c

@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright © 2022-2024 Rivos Inc.
+ * Copyright © 2023 FORTH-ICS/CARV
+ *
+ * RISCV IOMMU as a PCIe device
+ *
+ * Authors
+ *	Tomasz Jeznach <tjeznach@rivosinc.com>
+ *	Nick Kossifidis <mick@ics.forth.gr>
+ */
+
+#include <linux/compiler.h>
+#include <linux/init.h>
+#include <linux/iommu.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+
+#include "iommu-bits.h"
+#include "iommu.h"
+
+/* QEMU RISC-V IOMMU implementation */
+#define PCI_DEVICE_ID_REDHAT_RISCV_IOMMU     0x0014
+
+/* Rivos Inc. assigned PCI Vendor and Device IDs */
+#ifndef PCI_VENDOR_ID_RIVOS
+#define PCI_VENDOR_ID_RIVOS                  0x1efd
+#endif
+
+#define PCI_DEVICE_ID_RIVOS_RISCV_IOMMU_GA   0x0008
+
+static int riscv_iommu_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
+{
+	struct device *dev = &pdev->dev;
+	struct riscv_iommu_device *iommu;
+	int rc, vec;
+
+	rc = pcim_enable_device(pdev);
+	if (rc)
+		return rc;
+
+	if (!(pci_resource_flags(pdev, 0) & IORESOURCE_MEM))
+		return -ENODEV;
+
+	if (pci_resource_len(pdev, 0) < RISCV_IOMMU_REG_SIZE)
+		return -ENODEV;
+
+	rc = pcim_iomap_regions(pdev, BIT(0), pci_name(pdev));
+	if (rc)
+		return dev_err_probe(dev, rc, "pcim_iomap_regions failed\n");
+
+	iommu = devm_kzalloc(dev, sizeof(*iommu), GFP_KERNEL);
+	if (!iommu)
+		return -ENOMEM;
+
+	iommu->dev = dev;
+	iommu->reg = pcim_iomap_table(pdev)[0];
+
+	pci_set_master(pdev);
+	dev_set_drvdata(dev, iommu);
+
+	/* Check device reported capabilities / features. */
+	iommu->caps = riscv_iommu_readq(iommu, RISCV_IOMMU_REG_CAPABILITIES);
+	iommu->fctl = riscv_iommu_readl(iommu, RISCV_IOMMU_REG_FCTL);
+
+	/* The PCI driver only uses MSIs, make sure the IOMMU supports this */
+	switch (FIELD_GET(RISCV_IOMMU_CAPABILITIES_IGS, iommu->caps)) {
+	case RISCV_IOMMU_CAPABILITIES_IGS_MSI:
+	case RISCV_IOMMU_CAPABILITIES_IGS_BOTH:
+		break;
+	default:
+		return dev_err_probe(dev, -ENODEV,
+				     "unable to use message-signaled interrupts\n");
+	}
+
+	/* Allocate and assign IRQ vectors for the various events */
+	rc = pci_alloc_irq_vectors(pdev, 1, RISCV_IOMMU_INTR_COUNT,
+				   PCI_IRQ_MSIX | PCI_IRQ_MSI);
+	if (rc <= 0)
+		return dev_err_probe(dev, -ENODEV,
+				     "unable to allocate irq vectors\n");
+
+	iommu->irqs_count = rc;
+	for (vec = 0; vec < iommu->irqs_count; vec++)
+		iommu->irqs[vec] = msi_get_virq(dev, vec);
+
+	/* Enable message-signaled interrupts, fctl.WSI */
+	if (iommu->fctl & RISCV_IOMMU_FCTL_WSI) {
+		iommu->fctl ^= RISCV_IOMMU_FCTL_WSI;
+		riscv_iommu_writel(iommu, RISCV_IOMMU_REG_FCTL, iommu->fctl);
+	}
+
+	return riscv_iommu_init(iommu);
+}
+
+static void riscv_iommu_pci_remove(struct pci_dev *pdev)
+{
+	struct riscv_iommu_device *iommu = dev_get_drvdata(&pdev->dev);
+
+	riscv_iommu_remove(iommu);
+}
+
+static const struct pci_device_id riscv_iommu_pci_tbl[] = {
+	{PCI_VDEVICE(REDHAT, PCI_DEVICE_ID_REDHAT_RISCV_IOMMU), 0},
+	{PCI_VDEVICE(RIVOS, PCI_DEVICE_ID_RIVOS_RISCV_IOMMU_GA), 0},
+	{0,}
+};
+
+static struct pci_driver riscv_iommu_pci_driver = {
+	.name = KBUILD_MODNAME,
+	.id_table = riscv_iommu_pci_tbl,
+	.probe = riscv_iommu_pci_probe,
+	.remove = riscv_iommu_pci_remove,
+	.driver = {
+		.suppress_bind_attrs = true,
+	},
+};
+
+builtin_pci_driver(riscv_iommu_pci_driver);