Re: [PATCH v6 05/19] watchdog: orion: Make sure the watchdog is initially stopped

On Thu, Feb 06, 2014 at 06:02:56PM -0800, Guenter Roeck wrote:

On 02/06/2014 09:20 AM, Ezequiel Garcia wrote:

quoted

Having the watchdog initially fully stopped is important to avoid
any spurious watchdog triggers, in case the registers are not in
its reset state.

Reviewed-by: Guenter Roeck <redacted>
Tested-by: Sebastian Hesselbarth <redacted>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
---
  drivers/watchdog/orion_wdt.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/watchdog/orion_wdt.c b/drivers/watchdog/orion_wdt.c
index 6746033..2dbeee9 100644
--- a/drivers/watchdog/orion_wdt.c
+++ b/drivers/watchdog/orion_wdt.c

@@ -142,6 +142,9 @@ static int orion_wdt_probe(struct platform_device *pdev)
  	orion_wdt.max_timeout = wdt_max_duration;
  	watchdog_init_timeout(&orion_wdt, heartbeat, &pdev->dev);

+	/* Let's make sure the watchdog is fully stopped */
+	orion_wdt_stop(&orion_wdt);
+

Actually we just had that in another driver, and I stumbled over it there.

Problem with stopping the watchdog in probe unconditionally is that you can
use it to defeat nowayout: unload the module, then load it again,
and the watchdog is stopped even if nowayout is true.

Hm... I see.

Is this really what you want ? Or, in other words, what is the problem
you are trying to solve ?

Well, this is related to the discussion about the bootloader not
reseting the watchdog properly, provoking spurious watchdog triggering.

Jason Gunthorpe explained [1] that we needed a particular sequence:

 1. Disable WDT
 2. Clear bridge
 3. Enable WDT

We added the irq handling to satisfy (2), and the watchdog stop for (1).

The watchdog stop was agreed specifically [2].

Ideas?

[1] http://www.spinics.net/lists/arm-kernel/msg302340.html
[2] http://www.spinics.net/lists/arm-kernel/msg302507.html

-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html