linux-kernel - Re: [PATCH RFC] PM / Runtime: Rework the "runtime idle" helper routine

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Date:	Thu, 30 May 2013 09:05:43 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Alan Stern <stern@...land.harvard.edu>,
	Linux PM list <linux-pm@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Kevin Hilman <khilman@...aro.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH RFC] PM / Runtime: Rework the "runtime idle" helper routine

On 05/30/2013 06:18 AM, Rafael J. Wysocki wrote:
> On Wednesday, May 29, 2013 10:51:11 AM Alan Stern wrote:
>> On Wed, 29 May 2013, Rafael J. Wysocki wrote:
>>
>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>
>>> The "runtime idle" helper routine, rpm_idle(), currently ignores
>>> return values from .runtime_idle() callbacks executed by it.
>>>
>>> However, it turns out that many subsystems use the generic idle
>>> callback routine pm_generic_runtime_idle() which checks the return
>>> value of the driver's callback and executes pm_runtime_suspend() for
>>> the device unless that value is different from 0.  If that logic is
>>> moved to rpm_idle() instead, pm_generic_runtime_idle() can be dropped
>>> and its users will not need any .runtime_idle() callbacks any more.
>>
>> Since you're making this change, wouldn't it be a good idea to adopt
>> Mika's original suggestion and turn on the RPM_AUTO bit in rpmflags
>> when the use_autosuspend flag is set?
> 
> I'm not actually sure.  It can be done, but I'd prefer to do that as a separate
> change in any case.

For SCSI idle callback, that would be a welcome change, where instead of
calling pm_runtime_autosuspend and then return -EBUSY, it can be changed
to simply return 0 after mark_last_busy.

Thanks,
Aaron
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