linux-kernel - Re: [PATCH v2 6/7] Watchdog: introduce ARM SBSA watchdog driver

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Date:	Sun, 24 May 2015 10:32:31 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Timur Tabi <timur@...eaurora.org>, Fu Wei <fu.wei@...aro.org>
CC:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
	linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	Wei Fu <tekkamanninja@...il.com>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, vgandhi@...eaurora.org,
	wim@...ana.be, Jon Masters <jcm@...hat.com>,
	Leo Duran <leo.duran@....com>, Jon Corbet <corbet@....net>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 6/7] Watchdog: introduce ARM SBSA watchdog driver

On 05/24/2015 10:19 AM, Timur Tabi wrote:
> Fu Wei wrote:
>> I don't know why you want to do this tricky way.  you can always
>> register the interrupt handler,
>> if pre-timeout is 0, system will just trigger WS1 right after WS0
>
> But that only works if the pre-timeout and timeout can be programmed to separate values.  And as Guenter says, the SBSA may not guarantee that.
>

The pseudo-code in the specification suggests that if WCV is configured,
	WS0 = WCV
	WS1 = WCV + WOR

Assuming that the implementation follows the pseudo-code in the specification,
we would have separately programmable values. Since the pretimeout (per ABI)
is the difference in seconds to the timeout, and not an absolute value,
we would have to program the registers as follows.

	WCV = timeout - pretimeout;
	WOR = pretimeout;

Does this make sense ?

Thanks,
Guenter

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