linux-kernel - Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

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Message-ID: <CADyBb7tQMXt5_-15GKj91=ztT+Qbi2rV+gaG-=phVxbrF8Jgmw@mail.gmail.com>
Date:	Wed, 10 Jun 2015 22:41:04 +0800
From:	Fu Wei <fu.wei@...aro.org>
To:	Timur Tabi <timur@...eaurora.org>
Cc:	Guenter Roeck <linux@...ck-us.net>,
	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>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>, rjw@...ysocki.net
Subject: Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

On 10 June 2015 at 22:36, Fu Wei <fu.wei@...aro.org> wrote:
> On 10 June 2015 at 22:22, Timur Tabi <timur@...eaurora.org> wrote:
>> Fu Wei wrote:
>>>
>>> Another weakness of only using WOR is the timeout limited by this
>>> 32bit register.
>>> 10s @400MHz generic Timer
>>>
>>> I don't think this limit is good for a server, once the server is in a
>>> heavy load
>>
>>
>> Perhaps, but if that's the limitation of the hardware, then so be it.
>
> it is not the real limitation, if we use WCV, SBSA spec has mentioned that.
>
> ------ SBSA 2.3-------Page 23 ----------
> Note: the watchdog offset register is 32 bits wide. This gives a
> maximum watch period of around 10s at a system
> counter frequency of 400MHz. If a larger watch period is required then
> the compare value can be programmed
> directly into the compare value register
> ------ SBSA 2.3-------Page 23 ----------

------ SBSA 2.3-------Page 24 ----------
0x010 – 0x013 WCV[31:0]
0x014 – 0x017 WCV[63:32]
Watchdog compare value.
*Read/Write* registers
containing the current value in the watchdog compare
register.
------ SBSA 2.3-------Page 24 ----------

>
> if some hardware doesn't support writing WCV,
> that means this hardware is non-standard SBSA watchdog.
>
>>
>> --
>> Sent by an employee of the Qualcomm Innovation Center, Inc.
>> The Qualcomm Innovation Center, Inc. is a member of the
>> Code Aurora Forum, hosted by The Linux Foundation.
>
>
>
> --
> Best regards,
>
> Fu Wei
> Software Engineer
> Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
> Ph: +86 21 61221326(direct)
> Ph: +86 186 2020 4684 (mobile)
> Room 1512, Regus One Corporate Avenue,Level 15,
> One Corporate Avenue,222 Hubin Road,Huangpu District,
> Shanghai,China 200021



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
Ph: +86 21 61221326(direct)
Ph: +86 186 2020 4684 (mobile)
Room 1512, Regus One Corporate Avenue,Level 15,
One Corporate Avenue,222 Hubin Road,Huangpu District,
Shanghai,China 200021
--
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