From: Aaron Lu <aaron.lu@intel.com>
To: Alan Stern <stern@rowland.harvard.edu>,
James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
Linux-pm mailing list <linux-pm@vger.kernel.org>,
SCSI development list <linux-scsi@vger.kernel.org>
Subject: Re: [PATCH v2] scsi: sr: use block layer runtime PM
Date: Sat, 07 Sep 2013 23:05:39 +0800 [thread overview]
Message-ID: <522B40C3.2080605@intel.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1309061153010.1165-100000@iolanthe.rowland.org>
On 09/06/2013 11:56 PM, Alan Stern wrote:
> On Fri, 6 Sep 2013, James Bottomley wrote:
>
>>> layer runtime PM. Accordingly, the SCSI bus layer runtime PM callback is
>>> simplified as all SCSI devices that implement runtime PM are now request
>>> based.
>>
>> OK, let's now try for a descriptive changelog. All SCSI devices
>> (including sr) are "request based". I think what you mean is "all SCSI
>> devices which implement runtime PM have an exposed block device"?
>
> Actually Aaron means "All SCSI drivers implementing runtime PM now use
> the block layer's request-based mechanism."
Exactly, thanks for the clarification Alan. I'll update changlog using
the above words in v3.
>
>>> Note that due to ODD will be polled every 2 seconds,
>>
>> Since the device will be polled every 2 seconds
>>
>>> for suspend to
>>> actually happen, the autosuspend_delay can not be set to more than 2
>>> seconds or the polling interval has to be increased.
>>
>> Is this true? What about event driven devices? Supposing a distro has
>> a different interval.
>>
>> How about
>>
>> If your Distribution polls the device, the autosuspend interval cannot
>> be set to longer than the polling interval otherwise the device will
>> never suspend.
>
> The default polling done by the kernel uses 2-second intervals. Of
> course, distributions and users can change this or disable it entirely.
What about:
Note that due to the device will be polled by kernel at a constant
interval specified at /sys/module/block/parameters/events_dfl_poll_msecs,
the default value is 2 seconds, the autosuspend delay cannot be set to
longer than the polling interval otherwise the device will never suspend.
Thanks,
Aaron
next prev parent reply other threads:[~2013-09-07 15:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-05 5:52 [PATCH] scsi: sr: use block layer runtime PM Aaron Lu
2013-09-05 14:25 ` Alan Stern
2013-09-06 1:36 ` Aaron Lu
2013-09-06 2:01 ` [PATCH v2] " Aaron Lu
2013-09-06 14:26 ` Alan Stern
2013-09-06 15:00 ` James Bottomley
2013-09-06 15:56 ` Alan Stern
2013-09-07 15:05 ` Aaron Lu [this message]
2013-09-07 15:22 ` Alan Stern
2013-09-07 14:45 ` Aaron Lu
2013-09-09 2:01 ` [PATCH v3] " Aaron Lu
2013-10-28 7:27 ` [RESEND PATCH " Aaron Lu
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