Re: [PATCH v2 0/4] watchdog: add driver for Renesas Gen3 WDT watchdogs

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Hi Günter,

On Mon, Apr 4, 2016 at 7:52 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> On Mon, Apr 04, 2016 at 07:02:45PM +0200, Geert Uytterhoeven wrote:
>> On Mon, Apr 4, 2016 at 5:25 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>> > On Mon, Apr 04, 2016 at 05:21:44PM +0200, Geert Uytterhoeven wrote:
>> >> On Mon, Apr 4, 2016 at 4:59 PM, Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote:
>> >> >> My Salvator-X reboots after timeout from "cat > /dev/watchdog0", but
>> >> >> it doesn't reboot through "reboot" or "reboot -f"?
>> >> >
>> >> > That sadly doesn't work on Gen3. From the RFC v5 cover letter:
>> >>
>> >> > ===
>> >> >
>> >> > * drop restart_handler since ARM64 uses PSCI firmware resets which do
>> >> >   not call restart handlers
>> >> >
>> >> > The last point was quite a bummer to me because plain reboot was the
>> >> > reason I wrote this driver ;) Well, so is life...
>> >>
>> >> That's indeed silly. Can't we have it as a low-priority restart handler, to
>> >
>> > Yes, it is. It defeats the purpose of restart handlers. PSCI reset should have
>> > been implemented as a high priority restart handler.
>>
>> Unfortunately that won't work: psci_sys_reset() doesn't return on failure.
>>
> You mean it just hangs ? That is bad. If that is the case, it is not reliable
> and thus should be a low priority (or at best medium priority) restart handler
> (which can be replaced with a working higher priority one).

On my Salvator-X board, it hangs. The call into PSCI doesn't return.
As this is firmware, it may depend on the version of the firmware.

>> We can still clear arm_pm_restart in platform code, though ;-)
>>
> I had originally planned to replace arm_pm_restart() completely with restart
> handlers. Maybe I should revive the effort ?

Perhaps. As I remember, it was not such a pretty experience?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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