Re: [PATCH V3] PM / Runtime: Defer resuming of the device in pm_runtime_force_resume()

From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	Kevin Hilman <khilman@kernel.org>,
	Lina Iyer <lina.iyer@linaro.org>,
	Jon Hunter <jonathanh@nvidia.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Andy Gross <andy.gross@linaro.org>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH V3] PM / Runtime: Defer resuming of the device in pm_runtime_force_resume()
Date: Sat, 19 Nov 2016 00:13:03 +0100	[thread overview]
Message-ID: <CAJZ5v0gxPzK=YVcG4kR+07VW8_NxfczNSyu+m8PtvE4=5dUxYA@mail.gmail.com> (raw)
In-Reply-To: <CAPDyKFozunxSTBY_vWbdOFRjSHOjpb+KKTJsdMj+dPpzNCyi-w@mail.gmail.com>

On Fri, Nov 18, 2016 at 11:50 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On 17 November 2016 at 22:00, Rafael J. Wysocki <rafael@kernel.org> wrote:
>> On Thu, Nov 17, 2016 at 9:21 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>> On 13 October 2016 at 16:58, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>>> When the pm_runtime_force_suspend|resume() helpers were invented, we still
>>>> had CONFIG_PM_RUNTIME and CONFIG_PM_SLEEP as separate Kconfig options.
>>>>
>>>> To make sure these helpers worked for all combinations and without
>>>> introducing too much of complexity, the device was always resumed in
>>>> pm_runtime_force_resume().
>>>>
>>>> More precisely, when CONFIG_PM_SLEEP was set and CONFIG_PM_RUNTIME was
>>>> unset, we needed to resume the device as the subsystem/driver couldn't
>>>> rely on using runtime PM to do it.
>>>>
>>>> As the CONFIG_PM_RUNTIME option was merged into CONFIG_PM a while ago, it
>>>> removed this combination, of using CONFIG_PM_SLEEP without the earlier
>>>> CONFIG_PM_RUNTIME.
>>>>
>>>> For this reason we can now rely on the subsystem/driver to use runtime PM
>>>> to resume the device, instead of forcing that to be done in all cases. In
>>>> other words, let's defer the runtime resume to a later point when it's
>>>> actually needed.
>>>>
>>>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>>>
>>> Rafael, this one is ready to be queued. Unless there are other objections.
>>
>> Not an objection, but I'd like to revisit this when the device
>> dependencies work gets in, as something similar may need to be done
>> for suppliers, in principle.
>
> I certainly think it would make sense to extend this approach to also
> respect device-dependencies.
>
> However, I suggest we deal with that as a second step, on top of
> $subject patch. It should not be a problem, as we don't have any users
> of device-dependencies that also uses
> pm_runtime_force_suspend|resume(), right?
>
> Queuing this now, also allow us to get this more widely tested, before
> we continue extending it for dependencies.

Fair enough.

Thanks,
Rafael