Re: [PATCH v2 3/7] iommu/riscv: Add RISC-V IOMMU PCIe device driver

From: Robin Murphy
Date: Thu Apr 18 2024 - 18:07:45 EST

On 2024-04-18 5:32 pm, Tomasz Jeznach wrote:
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.

Link: https://lore.kernel.org/qemu-devel/20240307160319.675044-1-dbarboza@xxxxxxxxxxxxxxxx/
Co-developed-by: Nick Kossifidis <mick@xxxxxxxxxxxx>
Signed-off-by: Nick Kossifidis <mick@xxxxxxxxxxxx>
Signed-off-by: Tomasz Jeznach <tjeznach@xxxxxxxxxxxx>
---
MAINTAINERS | 1 +
drivers/iommu/riscv/Kconfig | 6 ++
drivers/iommu/riscv/Makefile | 1 +
drivers/iommu/riscv/iommu-pci.c | 154 ++++++++++++++++++++++++++++++++
4 files changed, 162 insertions(+)
create mode 100644 drivers/iommu/riscv/iommu-pci.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 051599c76585..4da290d5e9db 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18975,6 +18975,7 @@ F: Documentation/devicetree/bindings/iommu/riscv,iommu.yaml
F: drivers/iommu/riscv/Kconfig
F: drivers/iommu/riscv/Makefile
F: drivers/iommu/riscv/iommu-bits.h
+F: drivers/iommu/riscv/iommu-pci.c
F: drivers/iommu/riscv/iommu-platform.c
F: drivers/iommu/riscv/iommu.c
F: drivers/iommu/riscv/iommu.h
diff --git a/drivers/iommu/riscv/Kconfig b/drivers/iommu/riscv/Kconfig
index d02326bddb4c..711326992585 100644
--- a/drivers/iommu/riscv/Kconfig
+++ b/drivers/iommu/riscv/Kconfig
@@ -14,3 +14,9 @@ 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
+ depends on RISCV_IOMMU && PCI_MSI
+ help
+ Support for the PCI implementation of RISC-V IOMMU architecture.

Similar comments as before.

diff --git a/drivers/iommu/riscv/Makefile b/drivers/iommu/riscv/Makefile
index e4c189de58d3..f54c9ed17d41 100644
--- a/drivers/iommu/riscv/Makefile
+++ b/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
diff --git a/drivers/iommu/riscv/iommu-pci.c b/drivers/iommu/riscv/iommu-pci.c
new file mode 100644
index 000000000000..9263c6e475be
--- /dev/null
+++ b/drivers/iommu/riscv/iommu-pci.c
@@ -0,0 +1,154 @@
+// 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@xxxxxxxxxxxx>
+ * Nick Kossifidis <mick@xxxxxxxxxxxx>
+ */
+
+#include <linux/compiler.h>
+#include <linux/init.h>
+#include <linux/iommu.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+
+#include "iommu-bits.h"
+#include "iommu.h"
+
+/* Rivos Inc. assigned PCI Vendor and Device IDs */
+#ifndef PCI_VENDOR_ID_RIVOS
+#define PCI_VENDOR_ID_RIVOS 0x1efd
+#endif
+
+#ifndef PCI_DEVICE_ID_RIVOS_IOMMU
+#define PCI_DEVICE_ID_RIVOS_IOMMU 0xedf1
+#endif
+
+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 = pci_enable_device_mem(pdev);
+ if (rc)
+ return rc;
+
+ rc = pci_request_mem_regions(pdev, KBUILD_MODNAME);
+ if (rc)
+ goto fail;
+
+ pci_set_master(pdev);
+
+ if (!(pci_resource_flags(pdev, 0) & IORESOURCE_MEM))
+ goto fail;
+
+ if (pci_resource_len(pdev, 0) < RISCV_IOMMU_REG_SIZE)
+ goto fail;
+
+ iommu = devm_kzalloc(dev, sizeof(*iommu), GFP_KERNEL);
+ if (!iommu)
+ goto fail;
+
+ iommu->dev = dev;
+ iommu->reg = pci_iomap(pdev, 0, RISCV_IOMMU_REG_SIZE);

Maybe consider some of the pcim_* devres helpers, to simplify cleanup/remove?

+
+ if (!iommu->reg)
+ goto fail;
+
+ dev_set_drvdata(dev, iommu);
+
+ /* Check device reported capabilities / features. */
+ iommu->caps = riscv_iommu_readq(iommu, RISCV_IOMMU_REG_CAP);
+ 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_CAP_IGS, iommu->caps)) {
+ case RISCV_IOMMU_CAP_IGS_MSI:
+ case RISCV_IOMMU_CAP_IGS_BOTH:
+ break;
+ default:
+ dev_err(dev, "unable to use message-signaled interrupts\n");
+ rc = -ENODEV;
+ goto fail_unmap;
+ }
+
+ /* 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) {
+ dev_err(dev, "unable to allocate irq vectors\n");
+ goto fail_unmap;
+ }
+ for (vec = 0; vec < rc; vec++) {
+ iommu->irqs[vec] = msi_get_virq(dev, vec);
+ if (!iommu->irqs[vec])

Can that ever fail if the loop is already bounded to the number of vectors successfully allocated?

+ break;
+ }
+ iommu->irqs_count = 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);
+ }
+
+ rc = riscv_iommu_init(iommu);
+ if (!rc)
+ return 0;
+
+fail_unmap:
+ iounmap(iommu->reg);
+ pci_free_irq_vectors(pdev);
+fail:
+ pci_release_regions(pdev);
+ pci_clear_master(pdev);
+ pci_disable_device(pdev);
+ return rc;
+}
+
+static void riscv_iommu_pci_remove(struct pci_dev *pdev)
+{
+ struct riscv_iommu_device *iommu = dev_get_drvdata(&pdev->dev);
+
+ riscv_iommu_remove(iommu);
+ iounmap(iommu->reg);
+ pci_free_irq_vectors(pdev);
+ pci_release_regions(pdev);
+ pci_clear_master(pdev);
+ pci_disable_device(pdev);
+}
+
+static const struct pci_device_id riscv_iommu_pci_tbl[] = {
+ {PCI_VENDOR_ID_RIVOS, PCI_DEVICE_ID_RIVOS_IOMMU,
+ PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0},
+ {0,}
+};
+
+MODULE_DEVICE_TABLE(pci, riscv_iommu_pci_tbl);
+
+static const struct of_device_id riscv_iommu_of_match[] = {
+ {.compatible = "riscv,pci-iommu",},
+ {},
+};
+
+MODULE_DEVICE_TABLE(of, riscv_iommu_of_match);
+
+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 = {
+ .of_match_table = riscv_iommu_of_match,

Does an of_match_table serve any functional purpose for a PCI driver? I can't find any other examples of this being done.

Thanks,
Robin.

+ .suppress_bind_attrs = true,
+ },
+};
+
+module_pci_driver(riscv_iommu_pci_driver);