linux-kernel - Re: [PATCH v16 2/5] iommu/arm-smmu: Invoke pm

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Message-ID: <3ccc3690-dc9d-56e7-e2d1-62e73a189bff@codeaurora.org>
Date:   Fri, 7 Sep 2018 15:08:02 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Tomasz Figa <tfiga@...omium.org>
Cc:     "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Joerg Roedel <joro@...tes.org>, joro@...tes.org,
        Rob Herring <robh+dt@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>,
        "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rob Clark <robdclark@...il.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>, sboyd@...nel.org,
        jcrouse@...eaurora.org, Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v16 2/5] iommu/arm-smmu: Invoke pm_runtime during probe,
 add/remove device

Hi Tomasz,


On 9/7/2018 2:46 PM, Tomasz Figa wrote:
> Hi Vivek,
>
> On Thu, Aug 30, 2018 at 11:46 PM Vivek Gautam
> <vivek.gautam@...eaurora.org> 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.
>> Global locks are also initialized before enabling runtime pm as the
>> runtime_resume() calls device_reset() which does tlb_sync_global()
>> that ultimately requires locks to be initialized.
>>
>> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
>> [vivek: Cleanup pm runtime calls]
>> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
>> Reviewed-by: Tomasz Figa <tfiga@...omium.org>
>> Tested-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>>   drivers/iommu/arm-smmu.c | 89 +++++++++++++++++++++++++++++++++++++++++++-----
>>   1 file changed, 81 insertions(+), 8 deletions(-)
> [snip]
>> @@ -2215,10 +2281,17 @@ 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_force_suspend(smmu->dev);
>> +       else
>> +               clk_bulk_disable(smmu->num_clks, smmu->clks);
>>
>> -       clk_bulk_disable_unprepare(smmu->num_clks, smmu->clks);
>> +       clk_bulk_unprepare(smmu->num_clks, smmu->clks);
> Aren't we missing pm_runtime_disable() here? We'll have the enable
> count unbalanced if the driver is removed and probed again.

pm_runtime_force_suspend() does a pm_runtime_disable() also if i am not 
wrong.
And, as mentioned in a previous thread [1], we were seeing a warning 
which we avoided
by keeping force_suspend().

[1] https://lkml.org/lkml/2018/7/8/124

Thanks
Vivek
>
> Also, if we add pm_runtime_disable(), we can reorder things a bit and
> simplify into:
>
>         arm_smmu_rpm_get(smmu);
>
>         /* Turn the thing off */
>         writel(sCR0_CLIENTPD, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
>
>         if (pm_runtime_enabled())
>                 pm_runtime_disable();
>          arm_smmu_rpm_put(smmu);
>
>          clk_bulk_disable_unprepare(smmu->num_clks, smmu->clks);
>
> Best regards,
> Tomasz