linux-kernel - watchdog: watchdog_stop_on

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Message-ID: <CAD56B7eAZ0hb0kuRbALONMAgvuhHjqrShVRwf1s93ZSbv8xqww@mail.gmail.com>
Date:   Mon, 18 Jan 2021 12:39:45 -0500
From:   Paul Thomas <pthomas8589@...il.com>
To:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-watchdog@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Michal Simek <michal.simek@...inx.com>
Subject: watchdog: watchdog_stop_on_reboot()

Hello,

I'm going through our out-of-tree commits, and was wondering if there
is anything to be done with this one. Basically we remove both
watchdog_stop_on_reboot() calls (not sure why there are two to begin
with):
--- a/drivers/watchdog/cadence_wdt.c
+++ b/drivers/watchdog/cadence_wdt.c
@@ -330,7 +330,6 @@ static int cdns_wdt_probe(struct platform_device *pdev)

        watchdog_init_timeout(cdns_wdt_device, wdt_timeout, dev);
        watchdog_set_nowayout(cdns_wdt_device, nowayout);
-       watchdog_stop_on_reboot(cdns_wdt_device);
        watchdog_set_drvdata(cdns_wdt_device, wdt);

        wdt->clk = devm_clk_get(dev, NULL);
@@ -359,7 +358,6 @@ static int cdns_wdt_probe(struct platform_device *pdev)

        spin_lock_init(&wdt->io_lock);

-       watchdog_stop_on_reboot(cdns_wdt_device);
        watchdog_stop_on_unregister(cdns_wdt_device);
        ret = devm_watchdog_register_device(dev, cdns_wdt_device);
        if (ret)

This seems to save us in certain conditions where the Software System
Reset fails[1]. I'm not sure if there's other use cases where you
really do want the watchdog to stop on reboot?

This is on an arm64 Zyny Ultrascale+ platform.

-Paul

[1] The one reproducible example of the Software System Reset failing
I have for our system is after a kernel oops from removing the
xilinx_dma module.
https://lore.kernel.org/lkml/CAD56B7d_9+0XuOBysxW=CADLTG_7RybBTM8hCYKSigB8ie8E_g@mail.gmail.com/