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

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Message-ID: <aedf3f32-68ae-566a-3735-ca4ec5c7559a@arm.com>
Date:   Tue, 25 Sep 2018 19:55:33 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>,
        Will Deacon <will.deacon@....com>
Cc:     Mark Rutland <mark.rutland@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, alex.williamson@...hat.com,
        Linux PM <linux-pm@...r.kernel.org>, sboyd@...nel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        open list <linux-kernel@...r.kernel.org>,
        "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, robh+dt <robh+dt@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Tomasz Figa <tfiga@...omium.org>
Subject: Re: [PATCH v16 2/5] iommu/arm-smmu: Invoke pm_runtime during probe,
 add/remove device

Hi Vivek,

On 2018-09-25 6:56 AM, Vivek Gautam wrote:
> Hi Robin, Will,
> 
> On Tue, Sep 18, 2018 at 8:41 AM Vivek Gautam
> <vivek.gautam@...eaurora.org> wrote:
>>
>> Hi Robin,
>>
>> On Fri, Sep 7, 2018 at 3:52 PM Vivek Gautam <vivek.gautam@...eaurora.org> wrote:
>>>
>>> On Fri, Sep 7, 2018 at 3:22 PM Tomasz Figa <tfiga@...omium.org> wrote:
>>>>
>>>> On Fri, Sep 7, 2018 at 6:38 PM Vivek Gautam <vivek.gautam@...eaurora.org> wrote:
>>>>>
>>>>> 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
>>>>
>>>> I see, thanks. I didn't realize that pm_runtime_force_suspend()
>>>> already disables runtime PM indeed. Sorry for the noise.
>>>
>>> Hi Tomasz,
>>> No problem. Thanks for looking back at it.
>>>
>>> Hi Robin,
>>> If you are fine with this series, then can you please consider giving
>>> Reviewed-by, so that we are certain that this series will go in the next merge
>>> window.
>>> Thanks
>>
>> Gentle ping.
>> You ack will be very helpful in letting Will pull this series for 4.20.
>> Thanks.
> 
> I would really appreciate if you could provide your ack for this series.
> Or if there are any concerns, I am willing to address them.

Apologies, I thought I'd replied to say I'd be getting to this shortly, 
but apparently not :(

FWIW, "shortly" is now tomorrow - I don't *think* there's anything 
outstanding, but given the number of subtleties we've turned up so far I 
do just want one last thorough double-check to make sure.

Thanks,
Robin.