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

[Qinxin Xia]

On 2026/3/14 03:58:44, Nicolin Chen <nicolinc at nvidia.com> wrote:
> 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
> 

I'll delete the unuse variable, but I'll keep this struct there for
extensions.
-- 
Thanks,
Qinxin