From: Dmitry Osipenko <digetx@gmail.com>
To: Ulf Hansson <ulf.hansson@linaro.org>,
"Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Thierry Reding" <thierry.reding@gmail.com>,
"Jonathan Hunter" <jonathanh@nvidia.com>,
"Viresh Kumar" <vireshk@kernel.org>,
"Stephen Boyd" <sboyd@kernel.org>,
"Peter De Schrijver" <pdeschrijver@nvidia.com>,
"Mikko Perttunen" <mperttunen@nvidia.com>,
"Peter Chen" <peter.chen@kernel.org>,
"Lee Jones" <lee.jones@linaro.org>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Nishanth Menon" <nm@ti.com>,
"Adrian Hunter" <adrian.hunter@intel.com>,
"Michael Turquette" <mturquette@baylibre.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
linux-tegra <linux-tegra@vger.kernel.org>,
"Linux PM" <linux-pm@vger.kernel.org>,
"Linux USB List" <linux-usb@vger.kernel.org>,
linux-staging@lists.linux.dev, linux-pwm@vger.kernel.org,
linux-mmc <linux-mmc@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
DTML <devicetree@vger.kernel.org>,
linux-clk <linux-clk@vger.kernel.org>,
"Mark Brown" <broonie@kernel.org>,
"Vignesh Raghavendra" <vigneshr@ti.com>,
"Richard Weinberger" <richard@nod.at>,
"Miquel Raynal" <miquel.raynal@bootlin.com>,
"Lucas Stach" <dev@lynxeye.de>, "Stefan Agner" <stefan@agner.ch>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"David Heidelberg" <david@ixit.cz>
Subject: Re: [PATCH v13 13/35] drm/tegra: gr2d: Support generic power domain and runtime PM
Date: Mon, 4 Oct 2021 18:57:11 +0300 [thread overview]
Message-ID: <f5b5e06a-71ed-1250-f0ad-692062e00e01@gmail.com> (raw)
In-Reply-To: <CAPDyKFpqs5gUcym4q+GuiJy13eXqjEnx-eFdUT4bQpcfPAOEYw@mail.gmail.com>
04.10.2021 14:01, Ulf Hansson пишет:
> On Fri, 1 Oct 2021 at 21:00, Dmitry Osipenko <digetx@gmail.com> wrote:
>>
>> 01.10.2021 17:55, Ulf Hansson пишет:
>>> On Fri, 1 Oct 2021 at 16:29, Dmitry Osipenko <digetx@gmail.com> wrote:
>>>>
>>>> 01.10.2021 16:39, Ulf Hansson пишет:
>>>>> On Mon, 27 Sept 2021 at 00:42, Dmitry Osipenko <digetx@gmail.com> wrote:
>>>>>>
>>>>>> Add runtime power management and support generic power domains.
>>>>>>
>>>>>> Tested-by: Peter Geis <pgwipeout@gmail.com> # Ouya T30
>>>>>> Tested-by: Paul Fertser <fercerpav@gmail.com> # PAZ00 T20
>>>>>> Tested-by: Nicolas Chauvet <kwizart@gmail.com> # PAZ00 T20 and TK1 T124
>>>>>> Tested-by: Matt Merhar <mattmerhar@protonmail.com> # Ouya T30
>>>>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>>>>> ---
>>>>>> drivers/gpu/drm/tegra/gr2d.c | 155 +++++++++++++++++++++++++++++++++--
>>>>>
>>>>> [...]
>>>>>
>>>>>> static int gr2d_remove(struct platform_device *pdev)
>>>>>> @@ -259,15 +312,101 @@ static int gr2d_remove(struct platform_device *pdev)
>>>>>> return err;
>>>>>> }
>>>>>>
>>>>>> + pm_runtime_dont_use_autosuspend(&pdev->dev);
>>>>>> + pm_runtime_disable(&pdev->dev);
>>>>>
>>>>> There is no guarantee that the ->runtime_suspend() has been invoked
>>>>> here, which means that clock may be left prepared/enabled beyond this
>>>>> point.
>>>>>
>>>>> I suggest you call pm_runtime_force_suspend(), instead of
>>>>> pm_runtime_disable(), to make sure that gets done.
>>>>
>>>> The pm_runtime_disable() performs the final synchronization, please see [1].
>>>>
>>>> [1]
>>>> https://elixir.bootlin.com/linux/v5.15-rc3/source/drivers/base/power/runtime.c#L1412
>>>
>>> pm_runtime_disable() end up calling _pm_runtime_barrier(), which calls
>>> cancel_work_sync() if dev->power.request_pending has been set.
>>>
>>> If the work that was punted to the pm_wq in rpm_idle() has not been
>>> started yet, we end up just canceling it. In other words, there are no
>>> guarantees it runs to completion.
>>
>> You're right. Although, in a case of this particular patch, the syncing
>> is actually implicitly done by pm_runtime_dont_use_autosuspend().
>>
>> But for drivers which don't use auto-suspend, there is no sync. This
>> looks like a disaster, it's a very common pattern for drivers to
>> 'put+disable'.
>>
>>> Moreover, use space may have bumped the usage count via sysfs for the
>>> device (pm_runtime_forbid()) to keep the device runtime resumed.
>>
>> Right, this is also a disaster in a case of driver removal.
>>
>>>> Calling pm_runtime_force_suspend() isn't correct because each 'enable'
>>>> must have the corresponding 'disable'. Hence there is no problem here.
>>>
>>> pm_runtime_force_suspend() calls pm_runtime_disable(), so I think that
>>> should be fine. No?
>>
>> [adding Rafael]
>>
>> Rafael, could you please explain how drivers are supposed to properly
>> suspend and disable RPM to cut off power and reset state that was
>> altered by the driver's resume callback? What we're missing? Is Ulf's
>> suggestion acceptable?
>>
>> The RPM state of a device is getting reset on driver's removal, hence
>> all refcounts that were bumped by the rpm-resume callback of the device
>> driver will be screwed up if device is kept resumed after removal. I
>> just verified that it's true in practice.
>
> Note that, what makes the Tegra drivers a bit special is that they are
> always built with CONFIG_PM being set (selected from the "SoC"
> Kconfig).
>
> Therefore, pm_runtime_force_suspend() can work for some of these
> cases. Using this, would potentially avoid the driver from having to
> runtime resume the device in ->remove(), according to the below
> generic sequence, which is used in many drivers.
>
> pm_runtime_get_sync()
> clk_disable_unprepare() (+ additional things to turn off the device)
> pm_runtime_disable()
> pm_runtime_put_noidle()
It's not a problem to change this patchset. The problem is that if
you'll grep mainline for 'pm_runtime_disable', you will find that there
are a lot of drivers in a potential trouble.
I'm proposing that we should change pm_runtime_disable() to perform the
syncing with this oneliner:
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index ec94049442b9..5c9f28165824 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1380,6 +1380,8 @@ EXPORT_SYMBOL_GPL(pm_runtime_barrier);
*/
void __pm_runtime_disable(struct device *dev, bool check_resume)
{
+ flush_work(&dev->power.work);
+
spin_lock_irq(&dev->power.lock);
if (dev->power.disable_depth > 0) {
Objections?
The sysfs rpm-forbid is a separate problem and it's less troublesome
since it requires root privileges. It's also not something that
userspace touches casually. For now I don't know what could be done
about it.
next prev parent reply other threads:[~2021-10-04 15:57 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-26 22:40 [PATCH v13 00/35] NVIDIA Tegra power management patches for 5.16 Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 01/35] opp: Change type of dev_pm_opp_attach_genpd(names) argument Dmitry Osipenko
2021-10-04 9:11 ` Viresh Kumar
2021-09-26 22:40 ` [PATCH v13 02/35] soc/tegra: Add devm_tegra_core_dev_init_opp_table_common() Dmitry Osipenko
2021-10-01 12:50 ` Ulf Hansson
2021-10-01 19:15 ` Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 03/35] soc/tegra: pmc: Disable PMC state syncing Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 04/35] soc/tegra: Don't print error message when OPPs not available Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 05/35] dt-bindings: clock: tegra-car: Document new clock sub-nodes Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 06/35] clk: tegra: Support runtime PM and power domain Dmitry Osipenko
2021-10-01 12:32 ` Ulf Hansson
2021-10-01 19:50 ` Dmitry Osipenko
2021-10-02 20:44 ` Dmitry Osipenko
2021-10-05 13:10 ` Ulf Hansson
2021-10-05 22:19 ` Dmitry Osipenko
2021-10-05 22:43 ` Dmitry Osipenko
2021-10-06 2:40 ` Dmitry Osipenko
2021-10-06 12:43 ` Ulf Hansson
2021-10-06 21:14 ` Dmitry Osipenko
2021-10-06 22:01 ` Dmitry Osipenko
2021-10-06 23:21 ` Dmitry Osipenko
2021-10-07 9:18 ` Ulf Hansson
2021-10-07 10:36 ` Dmitry Osipenko
2021-10-06 12:38 ` Ulf Hansson
2021-10-06 21:20 ` Dmitry Osipenko
2021-10-06 21:25 ` Dmitry Osipenko
2021-10-06 22:03 ` Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 07/35] dt-bindings: host1x: Document OPP and power domain properties Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 08/35] dt-bindings: host1x: Document Memory Client resets of Host1x, GR2D and GR3D Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 09/35] gpu: host1x: Add runtime PM and OPP support Dmitry Osipenko
2021-10-01 13:24 ` Ulf Hansson
2021-09-26 22:40 ` [PATCH v13 10/35] gpu: host1x: Add host1x_channel_stop() Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 11/35] drm/tegra: dc: Support OPP and SoC core voltage scaling Dmitry Osipenko
2021-10-01 13:27 ` Ulf Hansson
2021-10-16 15:36 ` Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 12/35] drm/tegra: hdmi: Add OPP support Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 13/35] drm/tegra: gr2d: Support generic power domain and runtime PM Dmitry Osipenko
2021-10-01 13:39 ` Ulf Hansson
2021-10-01 14:29 ` Dmitry Osipenko
2021-10-01 14:55 ` Ulf Hansson
2021-10-01 19:00 ` Dmitry Osipenko
2021-10-04 11:01 ` Ulf Hansson
2021-10-04 15:57 ` Dmitry Osipenko [this message]
2021-10-05 8:45 ` Ulf Hansson
2021-10-05 17:16 ` Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 14/35] drm/tegra: gr3d: " Dmitry Osipenko
2021-10-01 14:06 ` Ulf Hansson
2021-10-01 21:25 ` Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 15/35] drm/tegra: vic: Support system suspend Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 16/35] usb: chipidea: tegra: Add runtime PM and OPP support Dmitry Osipenko
2021-09-30 0:40 ` Dmitry Osipenko
2021-09-30 14:06 ` Peter Chen
2021-09-30 14:08 ` Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 17/35] bus: tegra-gmi: " Dmitry Osipenko
2021-10-01 14:18 ` Ulf Hansson
2021-09-26 22:40 ` [PATCH v13 18/35] pwm: tegra: " Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 19/35] mmc: sdhci-tegra: " Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 20/35] mtd: rawnand: tegra: " Dmitry Osipenko
2021-10-01 14:24 ` Ulf Hansson
2021-10-01 14:35 ` Dmitry Osipenko
2021-10-01 15:01 ` Ulf Hansson
2021-10-17 8:38 ` Dmitry Osipenko
2021-10-19 11:40 ` Ulf Hansson
2021-09-26 22:40 ` [PATCH v13 21/35] spi: tegra20-slink: Add " Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 22/35] media: dt: bindings: tegra-vde: Convert to schema Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 23/35] media: dt: bindings: tegra-vde: Document OPP and power domain Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 24/35] media: staging: tegra-vde: Support generic " Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 25/35] soc/tegra: fuse: Reset hardware Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 26/35] soc/tegra: fuse: Use resource-managed helpers Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 27/35] soc/tegra: regulators: Prepare for suspend Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 28/35] soc/tegra: pmc: Rename 3d power domains Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 29/35] soc/tegra: pmc: Rename core power domain Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 30/35] soc/tegra: pmc: Enable core domain support for Tegra20 and Tegra30 Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 31/35] ARM: tegra: Add OPP tables and power domains to Tegra20 device-trees Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 32/35] ARM: tegra: Add OPP tables and power domains to Tegra30 device-trees Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 33/35] ARM: tegra: Add Memory Client resets to Tegra20 GR2D, GR3D and Host1x Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 34/35] ARM: tegra: Add Memory Client resets to Tegra30 " Dmitry Osipenko
2021-09-26 22:40 ` [PATCH v13 35/35] ARM: tegra20/30: Disable unused host1x hardware Dmitry Osipenko
2021-10-01 14:36 ` [PATCH v13 00/35] NVIDIA Tegra power management patches for 5.16 Ulf Hansson
2021-10-01 14:40 ` Dmitry Osipenko
2021-10-01 15:02 ` Ulf Hansson
2021-10-04 9:11 ` Viresh Kumar
2021-10-04 14:52 ` Dmitry Osipenko
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