Re: [RFC PATCH 1/5] iommu/arm-smmu-v3: Add basic debugfs framework

[Nicolin Chen <nicolinc@nvidia.com>]

On Fri, Mar 13, 2026 at 06:43:47PM +0800, Qinxin Xia wrote:
> +/**
> + * smmu_debugfs_capabilities_show() - Display SMMU capabilities
> + * @seq: seq_file to write to
> + * @v: private data (SMMU device)

@v is not used

> +
> +/**
> + * arm_smmu_debugfs_setup() - Initialize debugfs for SMMU device
> + * @smmu: SMMU device to setup debugfs for
> + * @ioaddr: Physical base address of the SMMU device registers
> + *
> + * This function creates the basic debugfs directory structure for a SMMU device.

nit: an SMMU

Or maybe simply "@smmu"

> + *
> + * Return: 0 on success, negative error code on failure
> + */
> +int arm_smmu_debugfs_setup(struct arm_smmu_device *smmu, phys_addr_t ioaddr)
> +{
> +	struct arm_smmu_debugfs *debugfs;
> +	struct dentry *smmu_dir;
> +	char name[32];
> +	int ret;
> +
> +	/* Create root directory if it doesn't exist */
> +	mutex_lock(&arm_smmu_debugfs_lock);
> +	if (!smmuv3_root_dir) {
> +		smmuv3_root_dir = debugfs_create_dir("arm_smmu_v3",
> +						     iommu_debugfs_dir);
> +		if (!smmuv3_root_dir) {
> +			mutex_unlock(&arm_smmu_debugfs_lock);
> +			return -ENOMEM;
> +		}
> +	}
> +	mutex_unlock(&arm_smmu_debugfs_lock);
> +
> +	/* Allocate debugfs structure */
> +	debugfs = kzalloc(sizeof(*debugfs), GFP_KERNEL);

kzalloc_obj(*debugfs)

> 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 4d00d796f078..211a0c87507a 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -33,6 +33,10 @@
>  #include "arm-smmu-v3.h"
>  #include "../../dma-iommu.h"
>  
> +#ifdef CONFIG_ARM_SMMU_V3_DEBUGFS
> +static unsigned int arm_smmu_present;
> +#endif

Unused

> @@ -4909,6 +4913,12 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto err_disable;
>  
> +#ifdef CONFIG_ARM_SMMU_V3_DEBUGFS
> +	ret = arm_smmu_debugfs_setup(smmu, ioaddr);
> +	if (ret)
> +		dev_warn(dev, "Failed to create debugfs!\n");
> +#endif
> +
>  	/* And we're up. Go go go! */
>  	ret = iommu_device_sysfs_add(&smmu->iommu, dev, NULL,
>  				     "smmu3.%pa", &ioaddr);

Since name is all we wanted, maybe follow iommu_device_sysfs_add()
by passing in: 
   "const char *name, ..." instead of "phys_addr_t ioaddr"

> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index 3c6d65d36164..247f27426f6b 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -733,6 +733,15 @@ struct arm_smmu_impl_ops {
>  			  const struct iommu_user_data *user_data);
>  };
>  
> +#ifdef CONFIG_ARM_SMMU_V3_DEBUGFS
> +struct arm_smmu_debugfs {
> +	struct dentry *root_dir;

Unused

> +	struct dentry *smmu_dir;
> +	struct arm_smmu_device *smmu;

Unused

Nicolin