linux-kernel - RE: [PATCH v2 1/3] ata: ahci: Rename board_ahci

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Message-ID: <BL1PR12MB5157B104CF62D747587A0412E23E9@BL1PR12MB5157.namprd12.prod.outlook.com>
Date:   Fri, 25 Feb 2022 21:13:08 +0000
From:   "Limonciello, Mario" <Mario.Limonciello@....com>
To:     Hans de Goede <hdegoede@...hat.com>,
        Christoph Hellwig <hch@...radead.org>
CC:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        "open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers)" 
        <linux-ide@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "pmenzel@...gen.mpg.de" <pmenzel@...gen.mpg.de>
Subject: RE: [PATCH v2 1/3] ata: ahci: Rename board_ahci_mobile

[AMD Official Use Only]

> >>>> On Fri, Feb 25, 2022 at 12:11:11AM -0600, Mario Limonciello wrote:
> >>>>> This board definition was originally created for mobile devices to
> >>>>> designate default link power managmeent policy to influence runtime
> >>>>> power consumption.
> >>>>>
> >>>>> As this is interesting for more than just mobile designs, rename the
> >>>>> board to `board_ahci_low_power` to make it clear it is about default
> >>>>> policy.
> >>>>
> >>>> Is there any good reason to not just apply the policy to all devices
> >>>> by default?
> >>>
> >>> That sure would make this all cleaner.
> >>>
> >>> I think Hans knows more of the history here than anyone else.  I had
> >>> presumed there was some data loss scenarios with some of the older
> >>> chipsets.
> >>
> >> When I first introduced this change there were reports of crashes and
> >> data corruption caused by setting the policy to min_power, these were
> >> tied to some motherboards and/or to some drives.
> >>
> >> This is the whole reason why I only enabled this on a subset of all the
> >> AHCI chipsets.
> >>
> >> At least on devices with a chipset which is currently marked as
> >> mobile, the motherboard specific issues could be fixed with a BIOS
> >> update. But I doubt that similar BIOS fixes have also been rolled
> >> out to all desktop boards (and have been applied by all users),
> >> and I also don't know about older boards.
> >>
> >> So enabling this on all chipsets is definitely not without risks.
> >>
> >
> > This was before min_power_with_partial and min_power_with_dipm
> > were introduced though right?
> 
> The issues where some laptops needed BIOS updates was with fedora
> using min_power_with_dipm as default for mobile chipsets.
> 

Do you know if the drives actually supported slumber and partial? 
I wonder if that was the real problem that they were being set when
they shouldn't be.

I added something for this in 2/2 in the RFC series you can look at.

> >  Maybe another way to look at this
> > is to drop the policy min_power, which overall is dangerous.
> 
> Maybe, see above. I'm not going to block this if people want
> to give this a try, but it is going to require someone keeping
> a very close look at any issues popping up and we must be
> prepared to roll-back the change if necessary.
> 

Per Paul's suggestion I sent out v3 of this series and then I sent
out a separate RFC series (you're on CC).  For this type of
thing if y'all think it makes sense to do.