Re: [PATCH v8 1/3] iommu/arm-smmu: add NVIDIA implementation for dual ARM MMU-500 usage

[Jon Hunter]

On 30/06/2020 17:23, Krishna Reddy wrote:
>>> +struct arm_smmu_device *nvidia_smmu_impl_init(struct arm_smmu_device 
>>> +*smmu) {
>>> +	unsigned int i;
> ....
>>> +	for (i = 1; i < MAX_SMMU_INSTANCES; i++) {
>>> +		struct resource *res;
>>> +
>>> +		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
>>> +		if (!res)
>>> +			break;
> 
>> Currently this driver is only supported for Tegra194 which I understand has 3 SMMUs. Therefore, I don't feel that we should fail silently here, I think it is better to return an error if all 3 cannot be initialised.
> 
> Initialization of all the three SMMU instances is not necessary here.

That is not what I am saying.

> The driver can work with all the possible number of instances 1, 2 and 3 based on the DT config though it doesn't make much sense to use it with 1 instance.
> There is no silent failure here from driver point of view. If there is misconfig in DT, SMMU faults would catch issues.

I disagree and you should return a proper error here.

>>> +		nvidia_smmu->bases[i] = devm_ioremap_resource(smmu->dev, res);
>>> +		if (IS_ERR(nvidia_smmu->bases[i]))
>>> +			return ERR_CAST(nvidia_smmu->bases[i]);
> 
>> You want to use PTR_ERR() here.
> 
> PTR_ERR() returns long integer. 
> This function returns a pointer. ERR_CAST is the right one to use here. 

Ah yes, indeed. OK that's fine.

Jon

-- 
nvpublic