Re: [PATCH v9 3/5] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device

[Robin Murphy <robin.murphy@arm.com>]

On 13/03/18 08:55, Vivek Gautam wrote:
> From: Sricharan R <sricharan@codeaurora.org>
> 
> 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@codeaurora.org>
> [vivek: Cleanup pm runtime calls]
> Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
> Reviewed-by: Tomasz Figa <tfiga@chromium.org>
> ---
>   drivers/iommu/arm-smmu.c | 95 ++++++++++++++++++++++++++++++++++++++++++++----
>   1 file changed, 87 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index d5873d545024..56a04ae80bf3 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -268,6 +268,20 @@ static struct arm_smmu_option_prop arm_smmu_options[] = {
>   	{ 0, NULL},
>   };
>   
> +static inline int arm_smmu_rpm_get(struct arm_smmu_device *smmu)
> +{
> +	if (pm_runtime_enabled(smmu->dev))
> +		return pm_runtime_get_sync(smmu->dev);
> +
> +	return 0;
> +}
> +
> +static inline void arm_smmu_rpm_put(struct arm_smmu_device *smmu)
> +{
> +	if (pm_runtime_enabled(smmu->dev))
> +		pm_runtime_put(smmu->dev);
> +}
> +
>   static struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
>   {
>   	return container_of(dom, struct arm_smmu_domain, domain);
> @@ -913,11 +927,15 @@ 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 = arm_smmu_rpm_get(smmu);
> +	if (ret < 0)
> +		return;
> +
>   	/*
>   	 * Disable the context bank and free the page tables before freeing
>   	 * it.
> @@ -932,6 +950,8 @@ 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);
> +
> +	arm_smmu_rpm_put(smmu);
>   }
>   
>   static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
> @@ -1213,10 +1233,15 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>   		return -ENODEV;
>   
>   	smmu = fwspec_smmu(fwspec);
> +
> +	ret = arm_smmu_rpm_get(smmu);
> +	if (ret < 0)
> +		return ret;
> +
>   	/* Ensure that the domain is finalised */
>   	ret = arm_smmu_init_domain_context(domain, smmu);
>   	if (ret < 0)
> -		return ret;
> +		goto rpm_put;
>   
>   	/*
>   	 * Sanity check the domain. We don't support domains across
> @@ -1230,29 +1255,47 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>   	}
>   
>   	/* Looks ok, so add the device to the domain */
> -	return arm_smmu_domain_add_master(smmu_domain, fwspec);
> +	ret = arm_smmu_domain_add_master(smmu_domain, fwspec);
> +
> +rpm_put:
> +	arm_smmu_rpm_put(smmu);
> +	return ret;
>   }
>   
>   static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova,
>   			phys_addr_t paddr, size_t size, int prot)
>   {
>   	struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
> +	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> +	struct arm_smmu_device *smmu = smmu_domain->smmu;

Nit: please use arm_smmu_domain for ops as well (as it was before 
523d7423e21b), or consistently elide it for smmu - the mixture of both 
methods is just a horrible mess (here and in unmap).

> +	int ret;
>   
>   	if (!ops)
>   		return -ENODEV;
>   
> -	return ops->map(ops, iova, paddr, size, prot);
> +	arm_smmu_rpm_get(smmu);
> +	ret = ops->map(ops, iova, paddr, size, prot);
> +	arm_smmu_rpm_put(smmu);
> +
> +	return ret;
>   }
>   
>   static size_t arm_smmu_unmap(struct iommu_domain *domain, unsigned long iova,
>   			     size_t size)
>   {
>   	struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
> +	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> +	struct arm_smmu_device *smmu = smmu_domain->smmu;
> +	size_t ret;
>   
>   	if (!ops)
>   		return 0;
>   
> -	return ops->unmap(ops, iova, size);
> +	arm_smmu_rpm_get(smmu);
> +	ret = ops->unmap(ops, iova, size);
> +	arm_smmu_rpm_put(smmu);
> +
> +	return ret;
>   }
>   
>   static void arm_smmu_iotlb_sync(struct iommu_domain *domain)
> @@ -1407,14 +1450,22 @@ static int arm_smmu_add_device(struct device *dev)
>   	while (i--)
>   		cfg->smendx[i] = INVALID_SMENDX;
>   
> +	ret = arm_smmu_rpm_get(smmu);
> +	if (ret < 0)
> +		goto out_cfg_free;
> +
>   	ret = arm_smmu_master_alloc_smes(dev);

Nit: it would be easier to just do the rpm_put here; then you don't need 
to mess with the cleanup path.

>   	if (ret)
> -		goto out_cfg_free;
> +		goto out_rpm_put;
>   
>   	iommu_device_link(&smmu->iommu, dev);
>   
> +	arm_smmu_rpm_put(smmu);
> +
>   	return 0;
>   
> +out_rpm_put:
> +	arm_smmu_rpm_put(smmu);
>   out_cfg_free:
>   	kfree(cfg);
>   out_free:
> @@ -1427,7 +1478,7 @@ 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;
> @@ -1435,8 +1486,15 @@ static void arm_smmu_remove_device(struct device *dev)
>   	cfg  = fwspec->iommu_priv;
>   	smmu = cfg->smmu;
>   
> +	ret = arm_smmu_rpm_get(smmu);
> +	if (ret < 0)
> +		return;
> +
>   	iommu_device_unlink(&smmu->iommu, dev);
>   	arm_smmu_master_free_smes(fwspec);
> +
> +	arm_smmu_rpm_put(smmu);
> +
>   	iommu_group_remove_device(dev);
>   	kfree(fwspec->iommu_priv);
>   	iommu_fwspec_free(dev);
> @@ -2124,6 +2182,8 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>   		smmu->irqs[i] = irq;
>   	}
>   
> +	platform_set_drvdata(pdev, smmu);
> +
>   	err = devm_clk_bulk_get(smmu->dev, smmu->num_clks, smmu->clks);
>   	if (err)
>   		return err;
> @@ -2132,6 +2192,19 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>   	if (err)
>   		return err;
>   
> +	/*
> +	 * We want to avoid touching dev->power.lock in fastpaths unless
> +	 * it's really going to do something useful - pm_runtime_enabled()
> +	 * can serve as an ideal proxy for that decision. So, conditionally
> +	 * enable pm_runtime.
> +	 */
> +	if (dev->pm_domain)
> +		pm_runtime_enable(dev);
> +
> +	err = arm_smmu_rpm_get(smmu);
> +	if (err < 0)
> +		return err;
> +
>   	err = arm_smmu_device_cfg_probe(smmu);
>   	if (err)
>   		return err;
> @@ -2173,10 +2246,11 @@ 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);
>   
> +	arm_smmu_rpm_put(smmu);
> +
>   	/*
>   	 * For ACPI and generic DT bindings, an SMMU will be probed before
>   	 * any device which might need it, so we want the bus ops in place
> @@ -2212,8 +2286,13 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
>   	if (!bitmap_empty(smmu->context_map, ARM_SMMU_MAX_CBS))
>   		dev_err(&pdev->dev, "removing device with active domains!\n");
>   
> +	arm_smmu_rpm_get(smmu);
>   	/* Turn the thing off */
>   	writel(sCR0_CLIENTPD, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
> +	arm_smmu_rpm_put(smmu);
> +
> +	if (pm_runtime_enabled(smmu->dev))
> +		pm_runtime_disable(smmu->dev);
>   
>   	clk_bulk_unprepare(smmu->num_clks, smmu->clks);
>   

I don't know how runtime and system PM interact - does the reset in 
arm_smmu_pm_resume need special treatment as well, or is the device 
guaranteed to be powered up at that point by other means?

Robin.