[PATCH v3 0/6] Improved sysreset/watchdog uclass integration
Tom Rini
trini at konsulko.com
Mon Nov 8 17:05:18 CET 2021
On Mon, Nov 08, 2021 at 08:58:33AM -0700, Simon Glass wrote:
> Hi,
>
> On Sun, 7 Nov 2021 at 04:18, Heinrich Schuchardt
> <heinrich.schuchardt at canonical.com> wrote:
> >
> >
> >
> > On 11/6/21 14:53, Tom Rini wrote:
> > > On Sat, Nov 06, 2021 at 04:55:44AM +0100, Heinrich Schuchardt wrote:
> > >>
> > >>
> > >> On 11/6/21 02:52, Andre Przywara wrote:
> > >>> On Fri, 5 Nov 2021 18:56:34 -0400
> > >>> Tom Rini <trini at konsulko.com> wrote:
> > >>>
> > >>>> On Fri, Nov 05, 2021 at 09:38:50PM +0100, Heinrich Schuchardt wrote:
> > >>>>> On 11/5/21 20:17, Tom Rini wrote:
> > >>>>>> On Fri, Nov 05, 2021 at 07:37:02PM +0100, Heinrich Schuchardt wrote:
> > >>>>>>> On 11/5/21 17:12, Simon Glass wrote:
> > >>>>>>>> Hi,
> > >>>>>>>>
> > >>>>>>>> On Fri, 5 Nov 2021 at 08:21, Tom Rini <trini at konsulko.com> wrote:
> > >>>>>>>>>
> > >>>>>>>>> On Fri, Nov 05, 2021 at 12:14:47PM +0100, Stefan Roese wrote:
> > >>>>>>>>>> Hi Andre,
> > >>>>>>>>>>
> > >>>>>>>>>> Added Tom to Cc.
> > >>>>>>>>>>
> > >>>>>>>>>> On 05.11.21 11:04, Andre Przywara wrote:
> > >>>>>>>>>>> On Thu, 4 Nov 2021 20:02:41 -0600
> > >>>>>>>>>>> Simon Glass <sjg at chromium.org> wrote:
> > >>>>>>>>>>>
> > >>>>>>>>>>> Hi,
> > >>>>>>>>>>>> On Thu, 4 Nov 2021 at 19:22, Stefan Roese <sr at denx.de> wrote:
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> Hi Andre,
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> On 05.11.21 00:11, Andre Przywara wrote:
> > >>>>>>>>>>>>>> On Thu, 4 Nov 2021 11:37:57 +0100
> > >>>>>>>>>>>>>> Stefan Roese <sr at denx.de> wrote:
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Hi Stefan,
> > >>>>>>>>>>>>>>> On 04.11.21 04:55, Samuel Holland wrote:
> > >>>>>>>>>>>>>>>> This series hooks up the watchdog uclass to automatically register
> > >>>>>>>>>>>>>>>> watchdog devices for use with sysreset, doing a bit of minor cleanup
> > >>>>>>>>>>>>>>>> along the way.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> The goal is for this to replace the sunxi board-level non-DM reset_cpu()
> > >>>>>>>>>>>>>>>> function. I was surprised to find that the wdt_reboot driver requires
> > >>>>>>>>>>>>>>>> its own undocumented device tree node, which references the watchdog
> > >>>>>>>>>>>>>>>> device by phandle. This is problematic for us, because sunxi-u-boot.dtsi
> > >>>>>>>>>>>>>>>> file covers 20 different SoCs with varying watchdog node phandle names.
> > >>>>>>>>>>>>>>>> So it would have required adding a -u-boot.dtsi file for each board.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> Hooking things up automatically makes sense to me; this is what Linux
> > >>>>>>>>>>>>>>>> does. However, I put the code behind a new option to avoid surprises for
> > >>>>>>>>>>>>>>>> other platforms.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> Changes in v3:
> > >>>>>>>>>>>>>>>> - Move condition to wdt-uclass.c to fix build errors.
> > >>>>>>>>>>>>>>>> - Include watchdog name in error message.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> Changes in v2:
> > >>>>>>>>>>>>>>>> - Extend the "if SYSRESET" block to the end of the file.
> > >>>>>>>>>>>>>>>> - Also make gpio_reboot_probe function static.
> > >>>>>>>>>>>>>>>> - Rebase on top of 492ee6b8d0e7 (now handle all watchdogs).
> > >>>>>>>>>>>>>>>> - Added patches 5-6 as an example of how the new option will be used.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> Samuel Holland (6):
> > >>>>>>>>>>>>>>>> sysreset: Add uclass Kconfig dependency to drivers
> > >>>>>>>>>>>>>>>> sysreset: Mark driver probe functions as static
> > >>>>>>>>>>>>>>>> sysreset: watchdog: Move watchdog reference to plat data
> > >>>>>>>>>>>>>>>> watchdog: Automatically register device with sysreset
> > >>>>>>>>>>>>>>>> sunxi: Avoid duplicate reset_cpu with SYSRESET enabled
> > >>>>>>>>>>>>>>>> sunxi: Use sysreset framework for poweroff/reset
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> arch/arm/Kconfig | 3 +++
> > >>>>>>>>>>>>>>>> arch/arm/mach-sunxi/board.c | 2 ++
> > >>>>>>>>>>>>>>>> drivers/sysreset/Kconfig | 11 ++++++--
> > >>>>>>>>>>>>>>>> drivers/sysreset/sysreset_gpio.c | 2 +-
> > >>>>>>>>>>>>>>>> drivers/sysreset/sysreset_resetctl.c | 2 +-
> > >>>>>>>>>>>>>>>> drivers/sysreset/sysreset_syscon.c | 2 +-
> > >>>>>>>>>>>>>>>> drivers/sysreset/sysreset_watchdog.c | 40 ++++++++++++++++++++++------
> > >>>>>>>>>>>>>>>> drivers/watchdog/wdt-uclass.c | 8 ++++++
> > >>>>>>>>>>>>>>>> include/sysreset.h | 10 +++++++
> > >>>>>>>>>>>>>>>> 9 files changed, 67 insertions(+), 13 deletions(-)
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> Applied to u-boot-marvell
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> Mmmh, why u-boot-marvell,
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> Because I'm handling watchdog related changed since a few years and we
> > >>>>>>>>>>>>> did not create a specific subsystem repo for this and I'm usually
> > >>>>>>>>>>>>> using my "marvell" one for this.
> > >>>>>>>>>
> > >>>>>>>>> And fwiw, there's a few other cases like this. If it's too confusing,
> > >>>>>>>>> maybe we should just roll out a few more repositories, I think it's
> > >>>>>>>>> easier to do that now than pre-gitlab?
> > >>>>>>>>>>>>>> and why did this end up already in master?
> > >>>>>>>>>>>>>> Isn't that material for the next merge window? After all this changes
> > >>>>>>>>>>>>>> quite a bit, for a lot of boards, and I did not have a closer look at
> > >>>>>>>>>>>>>> the sunxi parts yet.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> I was hesitating also a bit. But since this patchset is on the list in
> > >>>>>>>>>>>>> v1 since over 2 months now (2021-08-21) I thought it was "ready" for
> > >>>>>>>>>>>>> inclusion now. We are at -rc1 and I think we still have enough time to
> > >>>>>>>>>>>>> fix any resulting problems in this release cycle.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Why do we have the merge window then? This is clearly not a regression or
> > >>>>>>>>>>> general fix.
> > >>>>>>>>>>
> > >>>>>>>>>> AFAIU, we are a bit less strict here in U-Boot. Patches that were posted
> > >>>>>>>>>> before the merge-window and skipped the review process (most likely
> > >>>>>>>>>> because of lack of time) are often still integrated in the early rcX
> > >>>>>>>>>> cycles. At least this is how I handle it usually.
> > >>>>>>>>>>
> > >>>>>>>>>> Tom, is my understanding here correct?
> > >>>>>>>>>
> > >>>>>>>>> Yes. We are not as strict as the kernel is about what can come in
> > >>>>>>>>> between rc1 and rc2 (and to a certain degree, post rc2). I leave things
> > >>>>>>>>> up to the discretion of the custodians. People tend of have less time
> > >>>>>>>>> to handle U-Boot changes than other stuff, so I try and be flexible in
> > >>>>>>>>> picking things up.
> > >>>>>>>>>>>> Yes I agree, that should be plenty of time for people to review it.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Well, if there would be people to review the sunxi parts :-(
> > >>>>>>>>>>> I am totally fine with the generic patches (as they have been reviewed),
> > >>>>>>>>>>> but the sunxi integration is somewhat risky.
> > >>>>>>>>>>> I was explicitly deprioritising that in my queue, as it really doesn't
> > >>>>>>>>>>> change, add or fix anything, it's mere refactoring, from the user's point
> > >>>>>>>>>>> of view.
> > >>>>>>>>>>>>> Do you see any specific issues?
> > >>>>>>>>>>>
> > >>>>>>>>>>> Patch 6/6 changes the config for all 157 Allwinner boards, so I think that
> > >>>>>>>>>>> deserves at least some testing, *before* merging it.
> > >>>>>>>>>>
> > >>>>>>>>>> I expect that Samuel did some testing. But still, I agree that it
> > >>>>>>>>>> would be much better, if these patches - especially the Allwinner parts
> > >>>>>>>>>> got more extensive testing.
> > >>>>>>>>>>> I will do as much testing now as possible, but I am not happy about that
> > >>>>>>>>>>> situation.
> > >>>>>>>>>>
> > >>>>>>>>>> Understood. Should we revert patch 6/6 for now?
> > >>>>>>>>>
> > >>>>>>>>> FWIW, given Samuel has been doing a number of allwinner changes, I had
> > >>>>>>>>> also assumed it was sufficiently tested, which is why I didn't raise a
> > >>>>>>>>> further concern when I saw the widespread nature of the overall changes,
> > >>>>>>>>> just figured it was a few more ready-to-go cleanups that weren't quite
> > >>>>>>>>> picked up in time. Please do speak up if you want me to revert the last
> > >>>>>>>>> part.
> > >>>>>>>>
> > >>>>>>>> Also it is often true that people find problems by testing on master
> > >>>>>>>> so applying it helps to shake the tree a bit.
> > >>>>>>>>
> > >>>>>>>> Regards,
> > >>>>>>>> Simon
> > >>>>>>>
> > >>>>>>> We don't actually have a problem with this series but with a previous
> > >>>>>>> watchdog patch. The culprit according to bisecting is:
> > >>>>>>>
> > >>>>>>> b147bd3607f8 ("sunxi: Enable watchdog timer support by default")
> > >>>>>>>
> > >>>>>>> When booting the OrangePi PC the watchdog triggers while Linux is booting,
> > >>>>>>> ca. 16 s after leaving the UEFI subsystem. This matches WDT_MAX_TIMEOUT in
> > >>>>>>> drivers/watchdog/sunxi_wdt.c.
> > >>>>>>>
> > >>>>>>> If I run
> > >>>>>>> => wdt dev watchdog at 1c20ca0
> > >>>>>>> => wdt stop
> > >>>>>>>
> > >>>>>>> before the bootefi command booting succeeds.
> > >>>>>>>
> > >>>>>>> We don't disarm the watchdog and Linux does not do it for us in time.
> > >>>>>>>
> > >>>>>>> The UEFI specification requires that the default watchdog reset time is 300
> > >>>>>>> s. We should never arm the Sunxi hardware watchdog except within the
> > >>>>>>> watchdog reset driver.
> > >>>>>>>
> > >>>>>>> The solution is to disable CONFIG_WATCHDOG_AUTOSTART on SUNXI. See
> > >>>>>>>
> > >>>>>>> [PATCH 1/1] watchdog: don't autostart watchdog on Sunxi boards
> > >>>>>>> https://lists.denx.de/pipermail/u-boot/2021-November/466318.html
> > >>>>>>
> > >>>>>> This means we never did come up with a satisfactory to everyone solution
> > >>>>>> to what UEFI thinks a watchdog should do, and what other types of
> > >>>>>> deployment think a watchdog should do, yes?
> > >>>>>
> > >>>>> Dear Tom,
> > >>>>>
> > >>>>> The issue is *not* UEFI specific.
> > >>>>>
> > >>>>> A watchdog timeout of 16 seconds is too short for Linux to boot no matter
> > >>>>> whether you use the EFI stub or the legacy entry point.
> > >>>>>
> > >>>>> I only referred to the UEFI specification as it indicates what can be
> > >>>>> considered as a reasonable timeout interval: 300 seconds.
> > >>>>
> > >>>> 16 seconds from the last time we pet the watchdog in U-Boot to the
> > >>>> kernel being able to take over is quite reasonable.
> > >>>
> > >>> How do we know that the kernel takes over? What if the kernel/EFI
> > >>> payload doesn't have a watchdog driver? I was assuming that the
> > >>> watchdog would be disabled as soon as we boot a kernel or an EFI app
> > >>> calls ExitBootServices (maybe even earlier).
> > >>> But this sounds like a generic problem, not sunxi specific. So how do
> > >>> other platforms solve this?
> > >>>
> > >>> Cheers,
> > >>> Andre
> > >>
> > >> The UEFI specification has this requirement in chapter "3.1.2 Load Option
> > >> Processing":
> > >>
> > >> "... the boot manager must enable the watchdog timer for 5 minutes by using
> > >> the EFI_BOOT_SERVICES.SetWatchdogTimer() boot service prior to calling
> > >> EFI_BOOT_SERVICES.StartImage(). If a boot option returns control to the boot
> > >> manager, the boot manager must disable the watchdog timer with an additional
> > >> call to the SetWatchdogTimer() boot service."
> > >>
> > >> This means that having an armed watchdog when starting the kernel is
> > >> correct.
> > >>
> > >> If you start a watchdog in the firmware which is not disabled or reset by
> > >> the operating system, you are out of luck and won't be able to boot.
> > >>
> > >> Current Linux has driver drivers/watchdog/sunxi_wdt.c compatible to
> > >> "allwinner,sun4i-a10-wdt","allwinner,sun6i-a31-wdt" and enabled by
> > >> CONFIG_SUNXI_WATCHDOG. This driver was introduced in Linux v3.12. It
> > >> originally had compatible "allwinner,sun4i-wdt" only.
> > >>
> > >> Debian Bullseye has the driver enabled as a module. In the bootlog of the
> > >> Orange Pi PC I find:
> > >> [ 12.321909] sunxi-wdt 1c20ca0.watchdog: Watchdog enabled (timeout=16 sec,
> > >> nowayout=0)
> > >> This message appears approximately *20 seconds* after the EFI stub hands
> > >> over to the main kernel. Adding the driver to initrd shortens this to *18
> > >> seconds*. The message occurs after file system checks which can be a lengthy
> > >> operation. In Debian systemd manages the watchdog.
> > >>
> > >> As I said: 16 seconds is way too short for a hardware watchdog timeout.
> > >
> > > What's the time if you build it in?
> > >
> >
> > For sure you will find some board and configuration that is faster.
> >
> > But why should I care? This series breaks booting Debian on my board. So
> > it needs to be fixed. So, please, apply my patch that is doing so.
>
> Five minutes sounds completely unacceptable for embedded platforms.
> The user will surely have packaged the item up and will be just
> heading out to drop it off for return...
I'm trying to avoid bringing up the long discussion from the previous
thread about this :)
> Do we need to add a special case for UEFI here? E.g. bootefi could use
> a hook to lengthen the watchdog?
Well, the problem is that the hardware watchdog has a maximum period of
16 seconds, I believe.
--
Tom
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