Hi Oleksij, On Thu, 2018-03-08 at 15:16 +0100, Oleksij Rempel wrote: > > Also, it should be documented explicitly, that this will cause barebox > > to keep triggering the watchdog, even when it drops to the shell after > > a boot error. This makes it unsuitable for unattended use. > > I would prefer to use controlled reboot over uncontrolled watchdog reset. > For example it would be better to have boot and fail strategy. In case > of network boot, it would be better to retry download in some time and > not cause watchdog reset. If retry count exceeded then some thing should > be done. It can be power off, reboot, fall back to CLI.
In my experience, the watchdog is used as a last resort to handle any *unanticipated* problems. So, by definition, there isn't any code to handle these problems. The way to do this is that the watchdog is only triggered when the boot process has made actual progress towards a running system. For example: - once barebox probes the watchdog driver - from the shell init scripts - after loading the kernel, just before jumping to the kernel This way, there is no possible way which could cause barebox to just wait on the prompt: an idle or hung system will always be restarted via the watchdog. > The reason for controlled reboot is the fact that the reset impact (or > Reset Sensitivity) is different for every product and source of reset. > > This example is take from MiniRISC EZ4021-FC documentation: > Soft TAP Ctrl > Module Reset Reset PrRst ERst TRST Reset > CPU yes yes yes no no no > CP0 yes yes yes no no no > ICCi yes yes yes no no no > DCC yes yes yes no no no > BIU yes yes yes no no no > MMU yes no no no no no > MDU yes yes yes no no no > EJTAG iface: > - DMA/CPU Acc yes yes yes yes yes yes > logic > - Protocol engine yes no no yes yes yes > - Breakpoint yes no no yes no no > - PC trace yes no no yes no no It is not clear to me from this table which reset is triggered by the hardware watchdog. I would expect that it is the first column, which resets everything. > Most Atheros/QCA WiSoCs will not reset complete SoC even with watchdog > triggered reset. If you can't be sure that the watchdog resets enough to recover from any transient problem, you cannot rely on it at all (and should possibly use an external watchdog). Regards, Jan -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox
