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

[Robin Murphy <robin.murphy@arm.com>]

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@ventanamicro.com/
> Co-developed-by: Nick Kossifidis <mick@ics.forth.gr>
> Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>
> Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
> ---
>   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@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/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);

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