Re: [Linaro-acpi] [PATCH v8 5/5] Watchdog: introduce ARM SBSA watchdog driver

From: Guenter Roeck <linux@roeck-us.net>
To: Fu Wei <fu.wei@linaro.org>, Timur Tabi <timur@codeaurora.org>
Cc: Linaro ACPI Mailman List <linaro-acpi@lists.linaro.org>,
	linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org,
	lkml <linux-kernel@vger.kernel.org>,
	linux-doc@vger.kernel.org,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>,
	Jon Masters <jcm@redhat.com>, Pratyush Anand <panand@redhat.com>,
	Will Deacon <will.deacon@arm.com>,
	Wim Van Sebroeck <wim@iguana.be>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Wei Fu <tekkamanninja@gmail.com>,
	Rob Herring <robherring2@gmail.com>,
	Vipul Gandhi <vgandhi@codeaurora.org>,
	Dave Young <dyoung@redhat.com>
Subject: Re: [Linaro-acpi] [PATCH v8 5/5] Watchdog: introduce ARM SBSA watchdog driver
Date: Thu, 5 Nov 2015 08:41:03 -0800	[thread overview]
Message-ID: <563B869F.2010004@roeck-us.net> (raw)
In-Reply-To: <CADyBb7t6ovfrz1b3ZZykKq22HkZi1W0PWg7-wXihEjM9ciTgGg@mail.gmail.com>

On 11/05/2015 07:00 AM, Fu Wei wrote:
> Hi Timur,
>
> On 5 November 2015 at 22:40, Timur Tabi <timur@codeaurora.org> wrote:
>> Fu Wei wrote:
>>>
>>> Did you really read the "Note" above???????? OK, let me paste it again
>>> and again:
>>>
>>> SBSA 2.3 Page 23 :
>>> If a larger watch period is required then the compare value can be
>>> programmed directly into the compare value register.
>>
>>
>> Well, okay.  Sorry, I should have read what you pasted more closely. But I
>
> Thanks for reading it again.
>
>> think that means during initialization, not during the WS0 timeout.
>
> I really don't see SBSA say "during initialization, not during the WS0 timeout",
> please point it out the page number and the line number in SBSA spec.
> maybe I miss it?
> Thanks for your help in advance.
>
>>
>> Anyway, I still don't like the fact that you're programming WCV in the
>
> "you don't like" doesn't mean "it is wrong" or "we can't do this", so
> I will keep this way unless we have better idea to extend second stage
> timeout.
>
>> interrupt handler, but I'm not going to make a big deal about it any more.
>
> Deal, Thanks a lot.
>

The problem with your driver, as I see it, is that dealing with WS0/WS1
and pretimeout makes the driver so complex that, at least for my part,
I am very wary about it. The driver could long since have been accepted
if it were not for that. Besides that, I really believe that any system designer
using the highest permitted frequency should be willing to live with the
consequences, and not force the implementation of a a complex driver.

Ultimately, you'll have to decide if you want a simple driver accepted, or
a complex driver hanging in the review queue forever.

Thanks,
Guenter