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bh=gPEqd6cD/fqQw04EbCe32E6BIonMlduxm+Jx4+v1FHE=; b=NFsDDVSI3739 BFP/m9EezS79Uh7f+eZwoFR9ze53dIuj7/S/TYa1YgvCO2CXb7oskLS6ARti8hlH44YRPhEI4jdS6 18T//UjOyARN7Y8rnJ1CsxYcWfEWm8kYp/HF/0aUTqTBUTNskuaj3xy++H6R9g/p9ElUQr3AMA4p3 qae5rKX/wPSGSDI7xWmosRrRpLfwqiv8Q9zw6Fkvz5H0t0bX++xFMUhdC6BBhJzQhDoYeGBlht244 h6vP2l9oNoakywR/w7nGdp3NUlSgboaZu+jnMv8FckacgWi2NSIGRCjXFaWjGn2mOuMZj/8NOb1T0 oSR1/M2Of2T4N8+dD9/S4Q==; Received: from 108-223-40-66.lightspeed.sntcca.sbcglobal.net ([108.223.40.66]:42682) by bh-25.webhostbox.net with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.100.1) (envelope-from ) id 1xRfNK-00000003M8j-1MrI; Fri, 13 Nov 2026 06:12:42 +0530 Message-ID: <468e51cb-5852-4c8a-938d-bda2aca8c83e@roeck-us.net> Date: Thu, 12 Nov 2026 16:42:41 -0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/4] watchdog: vt8500: Add a restart handler To: Alexey Charkov , Krzysztof Kozlowski , Daniel Lezcano , Thomas Gleixner , Wim Van Sebroeck Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org References: <20261112-vt8500-timer-updates-v6-0-fd1cea645d1f@gmail.com> <20261112-vt8500-timer-updates-v6-4-fd1cea645d1f@gmail.com> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-BWhitelist: no X-Source-IP: 108.223.40.66 X-Source-L: No X-Exim-ID: 1xRfNK-00000003M8j-1MrI X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 108-223-40-66.lightspeed.sntcca.sbcglobal.net [108.223.40.66]:42682 X-Source-Auth: guenter@roeck-us.net X-Email-Count: 2 X-Org: HG=direseller_whb_net_legacy;ORG=directi; X-Source-Cap: cm9lY2s7YWN0aXZzdG07YmgtMjUud2ViaG9zdGJveC5uZXQ= X-Local-Domain: yes X-CMAE-Envelope: MS4xfGldJSQ2HtAjwKdwXn6gvo90nr79bnThCEYTv4atOvfd7233HAH9B213uuEkSLF2ODhUOXG7BcTBGvDC9+XilqgZn+FRPyIzmy5UBKGgVWoMPuV8WS8d WQqES73iIXqL8xcEcpfHaV0mkG2MBF5B9Q1OOiBWbaSoZdq6q8l1xkGeSIUpTEdAuuzuvNQPTtn8vk4UWRFF8TeXer1YFQ35UjHJ47cE2GZPYJXQ4wQXbs3U On 11/12/26 10:55, Alexey Charkov wrote: > Reset the SoC through the watchdog when the machine's own restart hook > leaves it running: the PMSR write in vt8500_restart() has no effect on > WM8950, so a reboot there ends in "Reboot failed -- System halted" > unless a watchdog armed from userspace happens to fire. > > Arm the match a millisecond ahead of the current count, which leaves > ample margin for the register writes to land. > > Register at priority 128, the default for restart handlers and also the > priority of the ARM machine restart hook. That hook is registered first, > from setup_arch(), and handlers of equal priority run in registration > order, so this one runs right after it and only matters where the hook > fails to reset the SoC. This isn't really the idea of restart handlers. The sequence should be well defined. That is what the priorities are for. Why not give it a slightly lower priority ? > > Signed-off-by: Alexey Charkov > --- > drivers/watchdog/vt8500-wdt.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/drivers/watchdog/vt8500-wdt.c b/drivers/watchdog/vt8500-wdt.c > index e0f838fd1d50..0ce1e2b06410 100644 > --- a/drivers/watchdog/vt8500-wdt.c > +++ b/drivers/watchdog/vt8500-wdt.c > @@ -25,6 +25,9 @@ > > #define VT8500_WDT_DEFAULT_TIMEOUT 30 /* seconds */ > > +/* How far ahead of the current count to arm the match for a restart */ > +#define VT8500_WDT_RESTART_TICKS (VT8500_TIMER_HZ / 1000) /* 1 ms */ > + > static bool nowayout = WATCHDOG_NOWAYOUT; > module_param(nowayout, bool, 0); > MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" > @@ -75,9 +78,18 @@ static int vt8500_watchdog_stop(struct watchdog_device *wdd) > return 0; > } > > +static int vt8500_watchdog_restart(struct watchdog_device *wdd, > + unsigned long action, void *data) > +{ > + struct vt8500_wdt_info *info = watchdog_get_drvdata(wdd); > + > + return vt8500_watchdog_arm(info, VT8500_WDT_RESTART_TICKS); This sets a 1-ms timer and doesn't wait for it to fire, so the next restart handler (if it exists) will be called. That seems odd, and may introduce unexpected behavior. Is this intentional ? If so, it should be explained. Thanks, Guenter > +} > + > static const struct watchdog_ops vt8500_watchdog_ops = { > .start = vt8500_watchdog_start, > .stop = vt8500_watchdog_stop, > + .restart = vt8500_watchdog_restart, > }; > > static const struct watchdog_info vt8500_watchdog_info = { > @@ -107,6 +119,7 @@ static int vt8500_wdt_probe(struct auxiliary_device *auxdev, > info = container_of(auxdev, struct vt8500_wdt_info, auxdev); > watchdog_set_drvdata(wdd, info); > watchdog_set_nowayout(wdd, nowayout); > + watchdog_set_restart_priority(wdd, 128); > > /* Let the core feed a watchdog left running, e.g. across kexec */ > if (readl(info->regbase + VT8500_WDT_EN_REG) & VT8500_WDT_EN) >