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

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Date:   Fri, 25 Feb 2022 16:19:30 +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

[Public]

> On 2/25/22 17:04, Limonciello, Mario wrote:
> > [Public]
> >
> >> 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?  Maybe another way to look at this
is to drop the policy min_power, which overall is dangerous.