From: Tom Rini <trini@konsulko.com>
To: u-boot@lists.denx.de
Subject: [PATCH 2/2] watchdog: add watchdog behavior configuration
Date: Wed, 23 Sep 2020 13:35:04 -0400 [thread overview]
Message-ID: <20200923173504.GV14816@bill-the-cat> (raw)
In-Reply-To: <8070fb73-d42b-fa66-98a6-a2b9926b2d3f@gmx.de>
On Wed, Sep 23, 2020 at 07:31:00PM +0200, Heinrich Schuchardt wrote:
> On 9/23/20 7:14 PM, Tom Rini wrote:
> > On Wed, Sep 23, 2020 at 07:01:54PM +0200, Mark Kettenis wrote:
> >>> From: Michael Walle <michael@walle.cc>
> >>> Date: Wed, 23 Sep 2020 18:45:27 +0200
> >>>
> >>> Let the user choose between three different behaviours of the watchdog:
> >>> (1) Keep the watchdog disabled
> >>> (2) Supervise u-boot
> >>> (3) Supervise u-boot and the operating systen (default)
> >>>
> >>> Option (2) will disable the watchdog right before handing control to the
> >>> operating system. This is useful when the OS is not aware of the
> >>> watchdog. Option (3) doesn't disable the watchdog and assumes the OS
> >>> will continue servicing.
> >>
> >> (3) can't be the default, at least for EFI
> >>
> >> The UEFI standard explicitly says that upon calling
> >> ExitBootServices(), the watchdog timer is disabled.
> >>
> >> In general, you can't expect an OS to have support for a particular
> >> watchdog timer. So (3) only makes sense in cases where U-Boot is
> >> bundled with an OS image.
> >
> > We need to be careful here then. The current and historical / generally
> > expected behavior is if we've enabled the watchdog we supervise it and
> > leave it enabled for the OS. Given what UEFI requires I'd like to see
> > that case handled with a print about disabling the watchdog so it's not
>
> Not printf(), maybe log_info().
>
> The disabling has to occur in ExitBootServices() (aka.
> efi_exit_boot_services()). Here we are in the middle of an executing
> UEFI application. Printing anything on the screen may mess up the output
> of the UEFI application.
>
> So, please, don't output anything.
We need to find a good way to inform the user we're disabling their
watchdog. Maybe before we fully jump in to UEFI note that it will be
disabled before entering the OS? Or something a bit more generally
understood than ExitBootServices() having been called. I don't know
_where_ the best place is, but I think it's important to inform the
user.
--
Tom
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next prev parent reply other threads:[~2020-09-23 17:35 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-23 16:45 [PATCH 1/2] watchdog: Hide WATCHDOG_RESET_DISABLE Michael Walle
2020-09-23 16:45 ` [PATCH 2/2] watchdog: add watchdog behavior configuration Michael Walle
2020-09-23 17:01 ` Mark Kettenis
2020-09-23 17:14 ` Tom Rini
2020-09-23 17:31 ` Heinrich Schuchardt
2020-09-23 17:35 ` Tom Rini [this message]
2020-09-24 7:33 ` Michael Walle
2020-09-24 8:10 ` Mark Kettenis
2020-09-24 8:20 ` Michael Walle
2020-09-24 10:22 ` Mark Kettenis
2020-09-24 21:05 ` Michael Walle
2020-09-24 13:19 ` Tom Rini
2020-09-24 20:30 ` Michael Walle
2020-09-24 20:58 ` Mark Kettenis
2020-09-24 21:14 ` Michael Walle
2020-09-25 1:17 ` Tom Rini
2020-09-25 8:36 ` Wolfgang Denk
2020-09-25 11:29 ` Heinrich Schuchardt
2020-09-25 13:00 ` Tom Rini
2020-09-25 13:26 ` Heinrich Schuchardt
2020-09-26 8:45 ` Wolfgang Denk
2020-09-26 10:54 ` Mark Kettenis
2020-09-26 12:39 ` Heinrich Schuchardt
2020-09-26 12:44 ` Tom Rini
2020-09-27 16:06 ` Michael Walle
2020-09-28 15:34 ` Tom Rini
2020-09-26 14:40 ` Wolfgang Denk
2020-09-26 14:22 ` Wolfgang Denk
2020-09-25 13:04 ` Wolfgang Denk
2020-10-04 14:55 ` Michael Walle
2020-10-04 15:10 ` Heinrich Schuchardt
2020-10-04 15:40 ` Tom Rini
2020-09-23 17:53 ` Mark Kettenis
2020-09-23 18:51 ` Heinrich Schuchardt
2020-09-23 19:02 ` Tom Rini
2020-09-23 20:01 ` Heinrich Schuchardt
2020-09-23 20:23 ` Tom Rini
2020-09-23 20:58 ` Heinrich Schuchardt
2020-09-23 21:09 ` Tom Rini
2020-09-23 20:38 ` Michael Walle
2020-09-23 21:01 ` Heinrich Schuchardt
2020-09-23 17:21 ` Heinrich Schuchardt
2020-09-23 17:28 ` Tom Rini
2020-09-24 6:53 ` Michael Walle
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