Re: [PATCH v6 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device

[Robin Murphy]

On 19/01/18 11:43, Vivek Gautam wrote:
> From: Sricharan R <sricharan@xxxxxxxxxxxxxx>
>
> The smmu device probe/remove and add/remove master device callbacks
> gets called when the smmu is not linked to its master, that is without
> the context of the master device. So calling runtime apis in those places
> separately.
>
> Signed-off-by: Sricharan R <sricharan@xxxxxxxxxxxxxx>
> [vivek: Cleanup pm runtime calls]
> Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
> ---
>   drivers/iommu/arm-smmu.c | 45 +++++++++++++++++++++++++++++++++++++++++----
>   1 file changed, 41 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 21acffe91a1c..95478bfb182c 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -914,11 +914,15 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
>   	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>   	struct arm_smmu_device *smmu = smmu_domain->smmu;
>   	struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> -	int irq;
> +	int ret, irq;
>   
>   	if (!smmu || domain->type == IOMMU_DOMAIN_IDENTITY)
>   		return;
>   
> +	ret = pm_runtime_get_sync(smmu->dev);
> +	if (ret)
> +		return;
> +
>   	/*
>   	 * Disable the context bank and free the page tables before freeing
>   	 * it.
> @@ -933,6 +937,8 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
>   
>   	free_io_pgtable_ops(smmu_domain->pgtbl_ops);
>   	__arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
> +
> +	pm_runtime_put_sync(smmu->dev);
>   }
>   
>   static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
> @@ -1408,12 +1414,20 @@ static int arm_smmu_add_device(struct device *dev)
>   	while (i--)
>   		cfg->smendx[i] = INVALID_SMENDX;
>   
> -	ret = arm_smmu_master_alloc_smes(dev);
> +	ret = pm_runtime_get_sync(smmu->dev);
>   	if (ret)
>   		goto out_cfg_free;
>   
> +	ret = arm_smmu_master_alloc_smes(dev);
> +	if (ret) {
> +		pm_runtime_put_sync(smmu->dev);
> +		goto out_cfg_free;

Please keep to the existing pattern and put this on the cleanup path 
with a new label, rather than inline.

> +	}
> +
>   	iommu_device_link(&smmu->iommu, dev);
>   
> +	pm_runtime_put_sync(smmu->dev);
> +
>   	return 0;
>   
>   out_cfg_free:
> @@ -1428,7 +1442,7 @@ static void arm_smmu_remove_device(struct device *dev)
>   	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
>   	struct arm_smmu_master_cfg *cfg;
>   	struct arm_smmu_device *smmu;
> -
> +	int ret;
>   
>   	if (!fwspec || fwspec->ops != &arm_smmu_ops)
>   		return;
> @@ -1436,8 +1450,21 @@ static void arm_smmu_remove_device(struct device *dev)
>   	cfg  = fwspec->iommu_priv;
>   	smmu = cfg->smmu;
>   
> +	/*
> +	 * The device link between the master device and
> +	 * smmu is already purged at this point.
> +	 * So enable the power to smmu explicitly.
> +	 */

I don't understand this comment, especially since we don't even 
introduce device links until the following patch... :/

> +
> +	ret = pm_runtime_get_sync(smmu->dev);
> +	if (ret)
> +		return;
> +
>   	iommu_device_unlink(&smmu->iommu, dev);
>   	arm_smmu_master_free_smes(fwspec);
> +
> +	pm_runtime_put_sync(smmu->dev);
> +
>   	iommu_group_remove_device(dev);
>   	kfree(fwspec->iommu_priv);
>   	iommu_fwspec_free(dev);
> @@ -2130,6 +2157,14 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>   	if (err)
>   		return err;
>   
> +	platform_set_drvdata(pdev, smmu);
> +
> +	pm_runtime_enable(dev);
> +
> +	err = pm_runtime_get_sync(dev);
> +	if (err)
> +		return err;
> +
>   	err = arm_smmu_device_cfg_probe(smmu);
>   	if (err)
>   		return err;
> @@ -2171,9 +2206,9 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>   		return err;
>   	}
>   
> -	platform_set_drvdata(pdev, smmu);
>   	arm_smmu_device_reset(smmu);
>   	arm_smmu_test_smr_masks(smmu);
> +	pm_runtime_put_sync(dev);
>   
>   	/*
>   	 * For ACPI and generic DT bindings, an SMMU will be probed before
> @@ -2212,6 +2247,8 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
>   
>   	/* Turn the thing off */
>   	writel(sCR0_CLIENTPD, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
> +	pm_runtime_force_suspend(smmu->dev);

Why do we need this? I guess it might be a Qualcomm-ism as I don't see 
anyone else calling it from .remove other than a couple of other qcom_* 
drivers. Given that we only get here during system shutdown (or the root 
user intentionally pissing about with driver unbinding), it doesn't seem 
like a point where power saving really matters all that much.

I'd also naively expect that anything this device was the last consumer 
off would get turned off by core code anyway once it's removed, but 
maybe things aren't that slick; I dunno :/

Robin.

> +
>   	return 0;
>   }
>