From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH v2 6/7] Watchdog: introduce ARM SBSA watchdog driver Date: Sun, 24 May 2015 09:58:05 -0700 Message-ID: <5562031D.3040808@roeck-us.net> References: <=fu.wei@linaro.org> <1432197156-16947-1-git-send-email-fu.wei@linaro.org> <1432197156-16947-7-git-send-email-fu.wei@linaro.org> <555DFCD4.3040701@codeaurora.org> <5560D7AC.50009@codeaurora.org> <5560DCB6.3090008@roeck-us.net> <5561DD0B.1040008@roeck-us.net> <5561FAFF.1050602@roeck-us.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Fu Wei Cc: Timur Tabi , Suravee Suthikulpanit , Linaro ACPI Mailman List , linux-watchdog-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Wei Fu , G Gregory , Al Stone , Hanjun Guo , Ashwin Chaugule , Arnd Bergmann , vgandhi-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, wim-IQzOog9fTRqzQB+pC5nmwQ@public.gmane.org, Jon Masters , Leo Duran , Jon Corbet , Mark Rutland List-Id: devicetree@vger.kernel.org On 05/24/2015 09:47 AM, Fu Wei wrote: > Hi Guenter, > > On 25 May 2015 at 00:23, Guenter Roeck wrote: >> On 05/24/2015 08:50 AM, Fu Wei wrote: >> [ ...] >> >>> Actually, I have added my thought at the head of sbsa_gwdt.c as a comment >>> : >>> >>> * >>> * Note: This SBSA Generic watchdog driver is compatible with >>> * the pretimeout concept of Linux kernel. >>> * The timeout and pretimeout are set by the different REGs. >>> * The first watch period is set by writing WCV directly, >>> * that can support more than 10s timeout at the maximum >>> * system counter frequency. >>> * The second watch period is set by WOR(32bit) which will be >>> loaded >>> * automatically by hardware, when WS0 is triggered. >>> * This gives a maximum watch period of around 10s at the maximum >>> * system counter frequency. >>> * The System Counter shall run at maximum of 400MHz. >>> * More details: DEN0029B - Server Base System Architecture (SBSA) >>> * >>> * Kernel/API: P---------| pretimeout >>> * |-------------------------------T timeout >>> * SBSA GWDT: P--WOR---WS1 pretimeout >>> * |-------WCV----------WS0~~~~~~~~T timeout >>> */ >>> >> >> Yes, but do we actually _know_ that it works that way, ie that WCV >> drives WS0 and that WOR drives WS1 ? Unless I am missing something, >> the specification doesn't say that, and it would have been a really >> easy statement to make if that was the intent. > > yes, Suravee has tested it on Seattle B0 Soc, that works. > But hope Suravee can provide more info about test, I will ping him later. > > According to SBSA, that WCV and WOR can both drive WS1 and WS0 > > the timeout and pretimeout in my patchset have been tested on Seattle > B0 and Foundation model. > >> >> My concern here is that the above behavior is not spelled out in >> the document, meaning it is up to interpretation by the hardware >> engineer implementing it, to the point where it appears that not >> even two software engineers can agree how it is supposed to work. >> Which is a really bad starting point :-(. > > Is that a real hardware teat can prove it works? > > or actually, SBSA say that it should work: > ----------------- > 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. > ----------------- > offset register == WOR > compare value register == WCV > Where does it say that WCV shall be associated with WS0 and that WOR shall be associated with WS1 ? Guess I am missing that part. Thanks, Guenter -- 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