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

    On 1/31/2018 6:36 PM, Robin Murphy wrote:
    > On 19/01/18 11:43, 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>
    >> ---
    >>   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.

    ok.

    >
    >> +    }
    >> +
    >>       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... :/
    >

    This is because the core device_del callback, does a device_links_purge for that device,
    before calling the remove_device notifier. As a result, have to explicitly turn on the
    power to iommu. Probably the comment should be removed, rest of the places we don't
    explain why we are turning on explicitly.

    >> +
    >> +    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 :/

    hmm, that should not be needed. with turning of all consumers taken care by device_link code before
    the supplier (iommu) remove gets called should ensure that. So the above force_suspend should
    not be needed/can be removed. But one more thing is, we do touch the register in the above code.
    So that should require a additional get/put sync around that writel.

    Regards,
    Sricharan

    --
    "QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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