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Message-ID: <b0f94951-2896-49a2-ac19-b885903067ad@arm.com>
Date: Tue, 25 Nov 2025 17:25:16 +0000
From: Robin Murphy <robin.murphy@....com>
To: Ashish Mhetre <amhetre@...dia.com>, will@...nel.org, joro@...tes.org,
robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, nicolinc@...dia.com
Cc: thierry.reding@...il.com, jonathanh@...dia.com, vdumpa@...dia.com,
jgg@...pe.ca, linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-tegra@...r.kernel.org
Subject: Re: [PATCH V2 1/3] iommu/arm-smmu-v3: Add device-tree support for
CMDQV driver
On 2025-11-25 7:16 am, Ashish Mhetre wrote:
> Add device tree support to the CMDQV driver to enable usage on Tegra264
> SoCs. The implementation parses the nvidia,cmdqv phandle from the SMMU
> device tree node to associate each SMMU with its corresponding CMDQV
> instance.
>
> Update the dependency from Kconfig as the driver now supports both
> ACPI and device tree initialization through conditional compilation.
>
> Add nvidia,tegra264-smmu to the arm-smmu-v3 device tree match table to
> enable device tree based probing on Nvidia Tegra264 platforms and
> restrict CMDQV usage to other vendors.
>
> Reviewed-by: Nicolin Chen <nicolinc@...dia.com>
> Signed-off-by: Ashish Mhetre <amhetre@...dia.com>
> ---
> drivers/iommu/arm/Kconfig | 2 +-
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 32 ++++++++++++++
> .../iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 43 ++++++++++++++++++-
> 3 files changed, 75 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/arm/Kconfig b/drivers/iommu/arm/Kconfig
> index ef42bbe07dbe..168ada9c3d68 100644
> --- a/drivers/iommu/arm/Kconfig
> +++ b/drivers/iommu/arm/Kconfig
> @@ -121,7 +121,7 @@ config ARM_SMMU_V3_KUNIT_TEST
>
> config TEGRA241_CMDQV
> bool "NVIDIA Tegra241 CMDQ-V extension support for ARM SMMUv3"
> - depends on ACPI
> + depends on OF || ACPI
This now does nothing, since ARM_SMMU_V3 depends on ARM64 which already
implies at least OF anyway.
> help
> Support for NVIDIA CMDQ-Virtualization extension for ARM SMMUv3. The
> CMDQ-V extension is similar to v3.3 ECMDQ for multi command queues
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index a33fbd12a0dd..2eec7cd4f3de 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -4530,6 +4530,34 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
> return 0;
> }
>
> +#ifdef CONFIG_TEGRA241_CMDQV
> +static void tegra_cmdqv_dt_probe(struct device_node *smmu_node,
> + struct arm_smmu_device *smmu)
> +{
> + struct platform_device *pdev;
> + struct device_node *np;
> +
> + np = of_parse_phandle(smmu_node, "nvidia,cmdqv", 0);
> + if (!np)
> + return;
> +
> + pdev = of_find_device_by_node(np);
> + of_node_put(np);
> + if (!pdev)
> + return;
> +
You need to drop the reference on the platform device too.
> + smmu->impl_dev = &pdev->dev;
> + smmu->options |= ARM_SMMU_OPT_TEGRA241_CMDQV;
> + dev_info(smmu->dev, "found companion CMDQV device: %s\n",
> + dev_name(smmu->impl_dev));
> +}
> +#else
> +static void tegra_cmdqv_dt_probe(struct device_node *smmu_node,
> + struct arm_smmu_device *smmu)
> +{
> +}
> +#endif
> +
> #ifdef CONFIG_ACPI
> #ifdef CONFIG_TEGRA241_CMDQV
> static void acpi_smmu_dsdt_probe_tegra241_cmdqv(struct acpi_iort_node *node,
> @@ -4634,6 +4662,9 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev,
> if (of_dma_is_coherent(dev->of_node))
> smmu->features |= ARM_SMMU_FEAT_COHERENCY;
>
> + if (of_device_is_compatible(dev->of_node, "nvidia,tegra264-smmu"))
> + tegra_cmdqv_dt_probe(dev->of_node, smmu);
> +
> return ret;
> }
>
> @@ -4867,6 +4898,7 @@ static void arm_smmu_device_shutdown(struct platform_device *pdev)
>
> static const struct of_device_id arm_smmu_of_match[] = {
> { .compatible = "arm,smmu-v3", },
> + { .compatible = "nvidia,tegra264-smmu", },
Since you're not using match data, this is pointless, as anything with
this compatible must still also match the generic compatible anyway.
Thanks,
Robin.
> { },
> };
> MODULE_DEVICE_TABLE(of, arm_smmu_of_match);
> diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> index 378104cd395e..2608bf6518b4 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> @@ -11,6 +11,8 @@
> #include <linux/iommufd.h>
> #include <linux/iopoll.h>
> #include <uapi/linux/iommufd.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
>
> #include <acpi/acpixf.h>
>
> @@ -917,6 +919,26 @@ tegra241_cmdqv_find_acpi_resource(struct device *dev, int *irq)
> return res;
> }
>
> +static struct resource *
> +tegra241_cmdqv_find_dt_resource(struct device *dev, int *irq)
> +{
> + struct platform_device *pdev = to_platform_device(dev);
> + struct resource *res;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res) {
> + dev_err(dev, "no memory resource found for CMDQV\n");
> + return NULL;
> + }
> +
> + if (irq)
> + *irq = platform_get_irq_optional(pdev, 0);
> + if (!irq || *irq <= 0)
> + dev_warn(dev, "no interrupt. errors will not be reported\n");
> +
> + return res;
> +}
> +
> static int tegra241_cmdqv_init_structures(struct arm_smmu_device *smmu)
> {
> struct tegra241_cmdqv *cmdqv =
> @@ -1048,11 +1070,14 @@ struct arm_smmu_device *tegra241_cmdqv_probe(struct arm_smmu_device *smmu)
>
> if (!smmu->dev->of_node)
> res = tegra241_cmdqv_find_acpi_resource(smmu->impl_dev, &irq);
> + else
> + res = tegra241_cmdqv_find_dt_resource(smmu->impl_dev, &irq);
> if (!res)
> goto out_fallback;
>
> new_smmu = __tegra241_cmdqv_probe(smmu, res, irq);
> - kfree(res);
> + if (!smmu->dev->of_node)
> + kfree(res);
>
> if (new_smmu)
> return new_smmu;
> @@ -1346,4 +1371,20 @@ tegra241_cmdqv_init_vintf_user(struct arm_vsmmu *vsmmu,
> return ret;
> }
>
> +static const struct of_device_id tegra241_cmdqv_of_match[] = {
> + { .compatible = "nvidia,tegra264-cmdqv" },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, tegra241_cmdqv_of_match);
> +
> +static struct platform_driver tegra241_cmdqv_driver = {
> + .driver = {
> + .name = "tegra241-cmdqv",
> + .of_match_table = tegra241_cmdqv_of_match,
> + },
> +};
> +module_platform_driver(tegra241_cmdqv_driver);
> +
> +MODULE_DESCRIPTION("NVIDIA Tegra241 Command Queue Virtualization Driver");
> +MODULE_LICENSE("GPL");
> MODULE_IMPORT_NS("IOMMUFD");
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