On Tue, Feb 13, 2018 at 1:54 PM, Tomasz Figa <tf...@chromium.org> wrote:
> Hi Vivek,
> Thanks for the patch. Please see my comments inline.
> On Wed, Feb 7, 2018 at 7:31 PM, Vivek Gautam
> <vivek.gau...@codeaurora.org> wrote:
>> From: Sricharan R <sricha...@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
>> Signed-off-by: Sricharan R <sricha...@codeaurora.org>
>> [vivek: Cleanup pm runtime calls]
>> Signed-off-by: Vivek Gautam <vivek.gau...@codeaurora.org>
>> drivers/iommu/arm-smmu.c | 42 ++++++++++++++++++++++++++++++++++++++----
>> 1 file changed, 38 insertions(+), 4 deletions(-)
>> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>> index 9e2f917e16c2..c024f69c1682 100644
>> --- a/drivers/iommu/arm-smmu.c
>> +++ b/drivers/iommu/arm-smmu.c
>> @@ -913,11 +913,15 @@ 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)
>> + ret = pm_runtime_get_sync(smmu->dev);
>> + if (ret)
>> + return;
> pm_runtime_get_sync() will return 0 if the device was powered off, 1
> if it was already/still powered on or runtime PM is not compiled in,
> or a negative value on error, so shouldn't the test be (ret < 0)?
Yes, I too noticed it while i was testing on a different platform, and
a failure case. Will update at all places.
> Moreover, I'm actually wondering if it makes any sense to power up the
> hardware just to program it and power it down again. In a system where
> the IOMMU is located within a power domain, it would cause the IOMMU
> block to lose its state anyway.
> Actually, reflecting back on "[PATCH v7 2/6] iommu/arm-smmu: Add
> pm_runtime/sleep ops", perhaps it would make more sense to just
> control the clocks independently of runtime PM? Then, runtime PM could
> be used for real power management, e.g. really powering the block up
> and down, for further power saving.
> +Generally similar comments for other places in this patch.
>> * Disable the context bank and free the page tables before freeing
>> * it.
>> @@ -932,6 +936,8 @@ static void arm_smmu_destroy_domain_context(struct
>> iommu_domain *domain)
>> __arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
>> + pm_runtime_put_sync(smmu->dev);
> Is there any point in the put being sync here?
No, I don't think. Can manage with just a 'put' here. Will modify.
>> @@ -2131,6 +2152,14 @@ static int arm_smmu_device_probe(struct
>> platform_device *pdev)
>> if (err)
>> return err;
>> + platform_set_drvdata(pdev, smmu);
>> + pm_runtime_enable(dev);
> I suspect this may be a disaster for systems where IOMMUs are located
> inside power domains, because the driver doesn't take care of the
> IOMMU block losing its state on physical power down, as I mentioned in
> my comments above.
> Best regards,
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
iommu mailing list