All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jisheng Zhang <jszhang@marvell.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Doug Anderson <dianders@chromium.org>,
	Wim Van Sebroeck <wim@iguana.be>,
	Heiko Stuebner <heiko@sntech.de>,
	Lunxue Dai <lunxue.dai@rock-chips.com>,
	Dinh Nguyen <dinguyen@altera.com>,
	"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] watchdog: dw_wdt: pat the watchdog before enabling it
Date: Tue, 27 Jan 2015 12:52:02 +0800	[thread overview]
Message-ID: <20150127125202.59dbd37d@xhacker> (raw)
In-Reply-To: <54C70F24.5080100@roeck-us.net>

Dear Guenter,

On Mon, 26 Jan 2015 20:08:04 -0800
Guenter Roeck <linux@roeck-us.net> wrote:

> On 01/26/2015 07:49 PM, Jisheng Zhang wrote:
> > Dear Doug,
> >
> > On Mon, 26 Jan 2015 15:27:15 -0800
> > Doug Anderson <dianders@chromium.org> wrote:
> >
> >> On some dw_wdt implementations the "top" register may be initted to 0
> >> at bootup.  In such a case, each "pat" of the watchdog will reset the
> >> timer to 0xffff.  That's pretty short.
> >>
> >> The input clock of the wdt can be any of a wide range of values.  On
> >> an rk3288 system, I've seen the wdt clock be 24.75 MHz.  That means
> >> each tick is ~40ns and we'll count to 0xffff in ~2.6ms.
> >>
> >> Because of the above two facts, it's a really good idea to pat the
> >> watchdog after initting the "top" register properly and before
> >> enabling the watchdog.  If you don't then there's no way we'll get the
> >> next heartbeat in time.
> >>
> >> Jisheng Zhang fixed this problem on some dw_mmc versions by using the
> >
> > s/dw_mmc/dw_wdt
> >
> >> TOP_INIT feature.  However, the dw_wdt on rk3288 doesn't have TOP_INIT
> >> so it's a good idea to also pat the watchdog manually.
> >
> > Based on your register dumping, I see the following configurations on
> > rk3288:
> >
> > WDT_DUAL_TOP is configured as false, so there's no TOP_INIT
> >
> > WDT_DFLT_TOP is configured as 0, so it will timeout soon.
> >
> >
> > So an extra pat is a must on such platforms with similar configurations.
> > And it doesn't hurt anything if we have an extra pat before enabling the
> > WDT
> >
> > All in all, except the "dw_mmc" typo above, the patch looks good to me.
> >
> 
> Jisheng,
> 
> it would be great if you can provide configuration information shown in
> the (undocumented) registers.

The wdt in rk3288 is a bit old, so I'm not sure whether the meaning is the same
or not. The key related configuration here is the so called CP_WDT_DUAL_TOP, bit[2]
of WDT_COMP_PARAMS_1 (0xf4), which indicates whether the TOP_INIT bits exist or
fixed as zero.

Thanks,
Jisheng

> 
> Doug,
> 
> can you send another version with this information added as comment
> to the code ? This will help others to understand what is going on
> (and why) later on.
> 
> Thanks,
> Guenter
> 


      reply	other threads:[~2015-01-27  4:55 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-26 23:27 [PATCH v2 1/2] watchdog: dw_wdt: pat the watchdog before enabling it Doug Anderson
2015-01-26 23:27 ` [PATCH v2 2/2] watchdog: dw_wdt: Try to get a 30 second watchdog by default Doug Anderson
2015-01-27  2:12 ` [PATCH v2 1/2] watchdog: dw_wdt: pat the watchdog before enabling it Guenter Roeck
2015-01-27  3:49 ` Jisheng Zhang
2015-01-27  4:08   ` Guenter Roeck
2015-01-27  4:52     ` Jisheng Zhang [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20150127125202.59dbd37d@xhacker \
    --to=jszhang@marvell.com \
    --cc=dianders@chromium.org \
    --cc=dinguyen@altera.com \
    --cc=heiko@sntech.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-watchdog@vger.kernel.org \
    --cc=linux@roeck-us.net \
    --cc=lunxue.dai@rock-chips.com \
    --cc=wim@iguana.be \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.