Hi Stefan,
Am 2020-09-21 11:01, schrieb Stefan Roese:
Hi Michael, Hi Chris,
On 15.09.20 12:44, Chris Packham wrote:
On Tue, 15 Sep 2020, 7:54 PM Michael Walle, michael@walle.cc wrote:
Am 2020-09-15 09:44, schrieb Rayagonda Kokatanur: > On Tue, Sep 15, 2020 at 12:56 PM Michael Wallemichael@walle.cc > wrote: >> >> Hi Stefan, >> >> it appears that since commit 06985289d45 ("watchdog: Implement generic >> watchdog_reset() version") - by default - the first watchdog is >> started >> unconditionally if CONFIG_WDT is set but never stopped before booting >> the operating system. >> >> Shouldn't it also be stopped uncondionally? What's worse is that on >> one >> board/arch the watchdog is stopped in arch_preboot_os() which is never >> called in the bootefi case. So even if I'd do a workaround and stop it >> manually in my board code, I couldn't do that consistently for >> bootm/bootefi. >> >> Or am I missing something here? > > Define CONFIG_WATCHDOG. > This takes care of resetting wdt.
Yes as along as you're inside the bootloader, but when u-boothands control over the OS the watchdog is not serviced anymore; which wouldn't be a problem per se, but it is enabled unconditionally by u-boot.
Just to add some data. At $dayjob we use this behaviour as a failsafe to make sure our userspace gets to a point where it is servicing the watchdog.
Yes, this is exactly how this is supposed to work AFAIK.
Michael, are you sure that the watchdog was disabled in U-Boot when booting into the OS before this patch?
If I read the patch correctly, it was per board, wasn't it?
At the moment you end up with a watchdog enabled if you have (a) CONFIG_WDT set, (b) A watchdog defined in the device tree
And no way to stop it reliably (well you could use some kind of bootcmd, but I don't think that is the way to go).
That said having a leave-wdt-running environment variable would work for our use case.
I would rather use it the other way around. Something like "wdt-stop- pre-os" to optionally stop the WDT before booting into the OS.
I'm fine with either one. At least I can stop the watchdog reliably.
OTOH a configuration option to not start a watchdog in the first place, should still be a valid choice.
Remark: IMHO, if you don't use the WDT in the OS, it does not make much sense to enable the WDT in U-Boot.
Keep in mind that my board is a "generic" module. I.e. there might be customers which may want to start a watchdog and there might be customers (that is also the debian-installer, for example) which doesn't want it or have no driver for it. This makes even more sense with EFI in place, which provides a universal boot method for any distribution/os (that might not be aware that a watchdog is running).
-michael