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Date: Thu, 21 May 2015 18:50:56 +0800 From: Fu Wei <fu.wei@...aro.org> To: Guenter Roeck <linux@...ck-us.net> 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>, Timur Tabi <timur@...eaurora.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 5/7] Watchdog: introduce "pretimeout" into framework Hi Guenter, Great thanks, I have got your review feedback, I will fix the problems :-) For update_limits, I also don't want to have that in the watchdog driver, and you can't find it in my last version. And this version, I integrate the watchdog_init_timeout and watchdog_init_pretimeout. so I can not add a driver specific "update_limits" between them. I think maybe we can not make this "update_limits" after calling init_timeouts, because we need to test and verify the timeout setting right after init_pretimeout by max_timeout and min_timeout. that is why I call update_limits right after init_pretimeout and before init_timeout. any suggestion ? Great thanks ! :-) On 21 May 2015 at 18:17, Guenter Roeck <linux@...ck-us.net> wrote: > On 05/21/2015 03:05 AM, Fu Wei wrote: >> >> Hi Guenter, >> >> Thanks for review. :-) >> feedback inline below >> >> On 21 May 2015 at 17:04, Guenter Roeck <linux@...ck-us.net> wrote: >>> >>> On 05/21/2015 01:32 AM, fu.wei@...aro.org wrote: >>>> >>>> >>>> From: Fu Wei <fu.wei@...aro.org> >>>> >>>> Also update Documentation/watchdog/watchdog-kernel-api.txt to >>>> introduce: >>>> (1)the new elements in the watchdog_device and watchdog_ops struct; >>>> (2)the new API "watchdog_init_timeouts". >>>> >>>> Reasons: >>>> (1)kernel already has two watchdog drivers are using "pretimeout": >>>> drivers/char/ipmi/ipmi_watchdog.c >>>> drivers/watchdog/kempld_wdt.c(but the definition is different) >>>> (2)some other dirvers are going to use this: ARM SBSA Generic Watchdog >>>> >>>> Signed-off-by: Fu Wei <fu.wei@...aro.org> >>>> --- >>> >>> >>> >>> [ ... ] >>> >>>> +extern int watchdog_init_timeouts(struct watchdog_device *wdd, >>>> + unsigned int pretimeout_parm, >>>> + unsigned int timeout_parm, >>>> + void (*update_limits)(struct >>>> watchdog_device *), >>>> + struct device *dev); >>>> >>>> -The watchdog_init_timeout function allows you to initialize the timeout >>>> field >>>> -using the module timeout parameter or by retrieving the timeout-sec >>>> property from >>>> -the device tree (if the module timeout parameter is invalid). Best >>>> practice is >>>> -to set the default timeout value as timeout value in the >>>> watchdog_device >>>> and >>>> -then use this function to set the user "preferred" timeout value. >>>> +The watchdog_init_timeouts function allows you to initialize the >>>> pretimeout and >>>> +timeout fields using the module pretimeout and timeout parameter or by >>>> +retrieving the elements in the timeout-sec property(the first element >>>> is >>>> for >>>> +timeout, the second one is for pretimeout) from the device tree(if the >>>> module >>>> +pretimeout and timeout parameter are invalid). >>>> +Normally, the pretimeout value will affect the limitation of timeout, >>>> and >>>> it >>>> +is also hardware related. So you can write a function in your driver to >>>> update >>>> +the limitation of timeout, according to the pretimeout value. Then pass >>>> the >>>> +function pointer by the update_limits parameter. If you driver doesn't >>>> +need this adjustment, just pass NULL to the update_limits parameter. >>> >>> >>> >>> You've lost me a bit with the update_limits function. >>> watchdog_init_timeouts() >>> is called from the driver. >> >> >> yes, that is the help function which will be called from watchdog >> driver, like SBSA watchdog driver >> >>> Why should the function have to call back into >>> the >>> driver to update the parameters which are passed from the driver ? >> >> >> Let me explain this, please correct me if I misunderstand something. >> According to the concept of "pretimeout" in kernel, the timeout >> contains the pretimeout, like >> >> * Kernel/API: P---------| pretimeout >> * |-------------------------------T timeout >> >> If you set up the value of pretimeout, that means pretimeout >> <min_timeout < timeout < max_timeout < (pretimeout + >> max_timeout_for_1th_stage) >> For min_timeout > pretimeout. if some one setup a timeout like : >> pretimeout > timeout > min_timeout, I think that could be a problem >> For max_timeout < (pretimeout + max_timeout_for_1th_stage), if some >> one setup a timeout like (pretimeout + max_timeout_for_1th_stage) < >> timeout > max_timeout . >> >> I have explained a little in doc, but the adjustment may have >> something to do with hardware, like max_timeout_for_1th_stage(in SBSA >> watchdog , limited by WCV) >> >> maybe this problem wouldn't happen ,if you set up max_timeout to a >> small number. so you can pass NULL to the pointer. >> but I think maybe for other device , that may happen. >> >>> Seems to me the driver can do that calculation first, then call >>> watchdog_init_timeouts() with the result. Am I missing something ? >> >> >> maybe I am overthinking it :-) >> please correct me >> > > I just sent a more complete review. In general I think this problem > (where the driver needs to update timeout limits based on the value of > pretimeout) is very driver specific, and should be kept in the driver. > I would prefer to keep it out of the API if possible. > > Unless I am missing something, it should be possible to call the > update_limits function in the driver after calling init_timeouts. > > Thanks, > Guenter > -- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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