Re: [RFC PATCH 4/5] iommu/arm-smmu-v3: Enable pm_runtime and setup devlinks

[Mostafa Saleh <smostafa@google.com>]

On Wed, Mar 19, 2025 at 12:42:53AM +0000, Pranjal Shrivastava wrote:
> Enable PM runtime for SMMUs having a power-domain during smmu probe.
> Add a devlink between the clients and SMMU device. The absence of a
> power domain effectively disables runtime power management.
> 
> Signed-off-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>

> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> 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 caf750470772..602784e84e84 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -3515,6 +3515,9 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
>  		pci_prepare_ats(to_pci_dev(dev), stu);
>  	}
>  
> +	device_link_add(dev, smmu->dev,
> +			DL_FLAG_PM_RUNTIME | DL_FLAG_AUTOREMOVE_SUPPLIER);
> +
>  	return &smmu->iommu;
>  
>  err_free_master:
> @@ -4836,11 +4839,18 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto err_disable;
>  
> +	if (dev->pm_domain) {
> +		pm_runtime_set_active(dev);
> +		pm_runtime_use_autosuspend(dev);
> +		pm_runtime_set_autosuspend_delay(dev, RPM_AUTOSUSPEND_DELAY_MS);
> +		pm_runtime_enable(dev);
> +	}
> +
>  	/* And we're up. Go go go! */
>  	ret = iommu_device_sysfs_add(&smmu->iommu, dev, NULL,
>  				     "smmu3.%pa", &ioaddr);
>  	if (ret)
> -		goto err_disable;
> +		goto err_rpm_disable;
>  
>  	ret = iommu_device_register(&smmu->iommu, &arm_smmu_ops, dev);
>  	if (ret) {
> @@ -4852,6 +4862,8 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>  
>  err_free_sysfs:
>  	iommu_device_sysfs_remove(&smmu->iommu);
> +err_rpm_disable:
> +	pm_runtime_disable(dev);
>  err_disable:
>  	arm_smmu_device_disable(smmu);
>  err_free_iopf:
> -- 
> 2.49.0.rc1.451.g8f38331e32-goog
>