From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Tomasz Figa <tfiga@chromium.org>,
Mark Rutland <mark.rutland@arm.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>, Linux PM <linux-pm@vger.kernel.org>,
Stephen Boyd <sboyd@kernel.org>,
Will Deacon <will.deacon@arm.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"list@263.net:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>, Rob Herring <robh+dt@kernel.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
freedreno <freedreno@lists.freedesktop.org>
Subject: Re: [PATCH v12 1/4] iommu/arm-smmu: Add pm_runtime/sleep ops
Date: Mon, 16 Jul 2018 12:23:12 +0200 [thread overview]
Message-ID: <CAJZ5v0irayU5cWBHtE=YVVqK_4gnue9bGopLkPY9P7-bEsixCA@mail.gmail.com> (raw)
In-Reply-To: <010cb56a-36e8-e729-1fe7-738048eb551d@codeaurora.org>
Hi,
On Mon, Jul 16, 2018 at 12:11 PM, Vivek Gautam
<vivek.gautam@codeaurora.org> wrote:
> HI Rafael,
>
>
>
> On 7/16/2018 2:21 PM, Rafael J. Wysocki wrote:
>>
>> On Thu, Jul 12, 2018 at 12:57 PM, Vivek Gautam
>> <vivek.gautam@codeaurora.org> wrote:
[cut]
>>>> Although, given the PM
>>>> subsystem internals, the suspend function wouldn't be called on SMMU
>>>> implementation needed power control (since they would have runtime PM
>>>> enabled) and on others, it would be called but do nothing (since no
>>>> clocks).
>>>>
>>>>> Honestly, I just don't know. :-)
>>>>>
>>>>> It just looks odd the way it is done. I think the clock should be
>>>>> gated during system-wide suspend too, because the system can spend
>>>>> much more time in a sleep state than in the working state, on average.
>>>>>
>>>>> And note that you cannot rely on runtime PM to always do it for you,
>>>>> because it may be disabled at a client device or even blocked by user
>>>>> space via power/control in sysfs and that shouldn't matter for
>>>>> system-wide PM.
>>>>
>>>> User space blocking runtime PM through sysfs is a good point. I'm not
>>>> 100% sure how the PM subsystem deals with that in case of system-wide
>>>> suspend. I guess for consistency and safety, we should have the
>>>> suspend callback.
>>>
>>> Will add the following suspend callback (same as
>>> arm_smmu_runtime_suspend):
>>>
>>> static int __maybe_unused arm_smmu_pm_suspend(struct device *dev)
>>> {
>>> struct arm_smmu_device *smmu = dev_get_drvdata(dev);
>>>
>>> clk_bulk_disable(smmu->num_clks, smmu->clks);
>>>
>>> return 0;
>>> }
>>
>> I think you also need to check if the clock has already been disabled
>> by runtime PM. Otherwise you may end up disabling it twice in a row.
>
>
> Should I rather call a pm_runtime_put() in suspend callback?
That wouldn't work as runtime PM may be effectively disabled by user
space via sysfs. That's one of the reasons why you need the extra
system-wide suspend callback in the first place. :-)
> Or an expanded form something similar to:
> https://elixir.bootlin.com/linux/v4.18-rc5/source/drivers/slimbus/qcom-ctrl.c#L695
Yes, you can do something like that, but be careful to make sure that
the state of the device after system-wide resume is consistent with
its runtime PM status in all cases.
next prev parent reply other threads:[~2018-07-16 10:23 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-08 17:34 [PATCH v12 0/4] iommu/arm-smmu: Add runtime pm/sleep support Vivek Gautam
2018-07-08 17:34 ` [PATCH v12 1/4] iommu/arm-smmu: Add pm_runtime/sleep ops Vivek Gautam
2018-07-11 9:50 ` Rafael J. Wysocki
2018-07-11 10:55 ` Vivek Gautam
2018-07-11 11:11 ` Rafael J. Wysocki
2018-07-11 12:51 ` Tomasz Figa
2018-07-11 13:40 ` Marek Szyprowski
2018-07-11 20:36 ` Rafael J. Wysocki
2018-07-23 5:59 ` Marek Szyprowski
2018-07-23 11:05 ` Rafael J. Wysocki
2018-07-12 10:57 ` Vivek Gautam
2018-07-16 8:51 ` Rafael J. Wysocki
2018-07-16 10:11 ` Vivek Gautam
2018-07-16 10:23 ` Rafael J. Wysocki [this message]
2018-07-08 17:34 ` [PATCH v12 2/4] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Vivek Gautam
2018-07-11 9:51 ` Rafael J. Wysocki
2018-07-11 10:05 ` Tomasz Figa
2018-07-11 10:59 ` Rafael J. Wysocki
2018-07-11 11:30 ` Vivek Gautam
2018-07-08 17:34 ` [PATCH v12 3/4] iommu/arm-smmu: Add the device_link between masters and smmu Vivek Gautam
2018-07-11 9:53 ` Rafael J. Wysocki
2018-07-11 10:36 ` Vivek Gautam
2018-07-12 12:41 ` Vivek Gautam
2018-07-16 8:55 ` Rafael J. Wysocki
2018-07-16 11:46 ` Vivek Gautam
2018-07-17 7:46 ` Rafael J. Wysocki
2018-07-17 8:30 ` Vivek Gautam
2018-07-18 9:30 ` Vivek Gautam
2018-07-18 12:43 ` Robin Murphy
2018-07-18 13:31 ` Vivek Gautam
2018-07-08 17:34 ` [PATCH v12 4/4] iommu/arm-smmu: Add support for qcom,smmu-v2 variant Vivek Gautam
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