linux-kernel - Re: [PATCH] SATA: Blacklist systems that spin off disks during ACPI power off

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Date:	Wed, 17 Sep 2008 17:50:54 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Tejun Heo <htejun@...il.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	linux-ide@...r.kernel.org, Thomas Renninger <trenn@...e.de>,
	Robert Hancock <hancockr@...w.ca>,
	LKML <linux-kernel@...r.kernel.org>,
	Frans Pop <elendil@...net.nl>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] SATA: Blacklist systems that spin off disks during ACPI
 power off

Rafael J. Wysocki wrote:
> On Sunday, 14 of September 2008, Jeff Garzik wrote:
>> Tejun Heo wrote:
>>> Rafael J. Wysocki wrote:
>>>> SATA: Blacklist systems that spin off disks during ACPI power off
>>>>
>>>> Some notebooks from HP have the problem that their BIOSes attempt to
>>>> spin down hard drives before entering ACPI system states S4 and S5.
>>>> This leads to a yo-yo effect during system power-off shutdown and the
>>>> last phase of hibernation when the disk is first spun down by the
>>>> kernel and then almost immediately turned on and off by the BIOS.
>>>> This, in turn, may result in shortening the disk's life times.
>>>>
>>>> To prevent this from happening we can blacklist the affected systems
>>>> using DMI information.  However, only the on-board controlles should
>>>> be blacklisted and their PCI slot numbers can be used for this
>>>> purpose.  Unfortunately the existing interface for checking DMI
>>>> information of the system is not very convenient for this purpose,
>>>> because to use it, we would have to define special callback functions
>>>> or create a separate struct dmi_system_id table for each blacklisted
>>>> system.
>>>>
>>>> To overcome this difficulty introduce a new function
>>>> dmi_first_match() returning a pointer to the first entry in an array
>>>> of struct dmi_system_id elements that matches the system DMI
>>>> information.  Then, we can use this pointer to access the entry's
>>>> .driver_data field containing the additional information, such as
>>>> the PCI slot number, allowing us to do the desired blacklisting.
>>>>
>>>> Introduce a new libata flag ATA_FLAG_NO_POWEROFF_SPINDOWN that, if
>>>> set, will prevent disks from being spun off during system power off
>>>> and hibernation (to handle the hibernation case we need a new system
>>>> state SYSTEM_HIBERNATE_ENTER that can be checked against by libata,
>>>> in analogy with SYSTEM_POWER_OFF).  Use dmi_first_match() to set this
>>>> flag for some systems affected by the problem described above (HP nx6325,
>>>> HP nx6310, HP 2510p).
>>>>
>>>> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
>>> libata part looks good to me but I think it would be better to
>>> separate out DMI changes into a separate patch.
>> Did these changes ever get separated out?
> 
> I only have the 'combo' patch if that's what you're asking about.  [The latest
> version is at http://bugzilla.kernel.org/attachment.cgi?id=17702&action=view]
> 
> Still, I can easily split the patch, although in that case the reason for the
> DMI changes won't be very clear without a reference to the SATA changes IMO.

That's the nature of every single API change -- you have the change, and 
then you have the users.

Respectfully, please split up the patch as requested, into DMI subsystem 
and ata subsystem pieces.

Re-reviewing the patch, I would even think that you should split out the 
kernel/power/disk and linux/kernel.h changes as well.

	Jeff




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