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Message-ID: <f580d22b-972f-3033-7a80-daea308c81f5@codeaurora.org>
Date: Thu, 1 Feb 2018 18:01:54 +0530
From: Vivek Gautam <vivek.gautam@...eaurora.org>
To: Sricharan R <sricharan@...eaurora.org>,
Robin Murphy <robin.murphy@....com>,
alex.williamson@...hat.com, robh+dt@...nel.org,
mark.rutland@....com, rjw@...ysocki.net, will.deacon@....com,
iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
sboyd@...eaurora.org
Cc: gregkh@...uxfoundation.org, m.szyprowski@...sung.com,
architt@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v6 3/6] iommu/arm-smmu: Invoke pm_runtime during probe,
add/remove device
On 2/1/2018 5:03 PM, Sricharan R wrote:
> 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@...eaurora.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@...eaurora.org>
>>> [vivek: Cleanup pm runtime calls]
>>> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.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.
Yes, will remove the comment here.
>
>>> +
>>> + 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.
Possibly we can replace the force_suspend() with a pm_runtime_disable()
to complement pm_runtime_enable in the probe.
I will test the scenario where we are writing the SMMU register in
.remove path.
regards
Vivek
>
> Regards,
> Sricharan
>
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