Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752381AbbEGR5z (ORCPT ); Thu, 7 May 2015 13:57:55 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:41385 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751763AbbEGR5w (ORCPT ); Thu, 7 May 2015 13:57:52 -0400 Date: Thu, 7 May 2015 10:57:47 -0700 From: Guenter Roeck To: "Opensource [Steve Twiss]" Cc: LINUXKERNEL , LINUXWATCHDOG , Wim Van Sebroeck , Alessandro Zummo , DEVICETREE , David Dajun Chen , Dmitry Torokhov , Ian Campbell , Kumar Gala , LINUXINPUT , Lee Jones , Liam Girdwood , Mark Brown , Mark Rutland , Pawel Moll , RTCLINUX , Rob Herring , Samuel Ortiz , Support Opensource Subject: Re: [PATCH V1 5/6] watchdog: da9062: DA9062 watchdog driver Message-ID: <20150507175747.GB30372@roeck-us.net> References: <2afd9f55c71553186e99bfe386312f0c7d7501ed.1429280614.git.stwiss.opensource@diasemi.com> <55327DDA.4080003@roeck-us.net> <6ED8E3B22081A4459DAC7699F3695FB7014B21924A@SW-EX-MBX02.diasemi.com> <20150506160227.GA28101@roeck-us.net> <6ED8E3B22081A4459DAC7699F3695FB7014B21925B@SW-EX-MBX02.diasemi.com> <20150506200631.GA25846@roeck-us.net> <6ED8E3B22081A4459DAC7699F3695FB7014B221DD2@SW-EX-MBX02.diasemi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6ED8E3B22081A4459DAC7699F3695FB7014B221DD2@SW-EX-MBX02.diasemi.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020201.554BA79F.027F,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.000 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 16 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4357 Lines: 93 On Thu, May 07, 2015 at 05:45:13PM +0000, Opensource [Steve Twiss] wrote: > On 06 May 2015 21:07 Guenter Roeck wrote: > > > > > > The DA9062 watchdog ping (register CONTROL_F) is "windowed" for protection > > > > > against spurious writes -- i.e. the ping function cannot be called within a 250ms > > > > > time limit or the PMIC will reset. This windowing protection also extends to altering > > > > > the timeout scale in the CONTROL_D register -- in which case if the timeout > > > > > register is altered and the ping() function is called within the 250ms limit, the > > > > > PMIC will reset. The delay is there to stop that from happening. > > > > > > > > > > I realised my previous patch was over-sanitised: by putting the time delay into the > > > > > ping() function I was protecting CONTROL_D in stop() and update_timeout_register(), > > > > > but I was being too over-protective of the ping() function. Therefore if there was an > > > > > "incorrect trigger signal", the watchdog would not be allowed to fail because the > > > > > driver would have filtered out the errors. > > > > > > > > > Hi Steve, > > > > > > > > From your description, it sounds like the protection is only necessary if there > > > > was a previous write to the same register(s). > > Hi Guenter, > > A clarification from me. It is not the CONTROL_D register that needs protecting, but when > the CONTROL_D register is altered the function call also performs a CONTROL_F watchdog > ping. Too many pings close together would cause the PMIC reset. > > > > > If so, it might make sense to record the time of such writes, and only add the delay > > > > if necessary, and only for the remainder of the time. > > I've tried it several ways, but my previous suggestion of putting the delays in the stop() and > update_timeout_register() functions just cause even more lengthy delays. > > So, I've followed your suggestion and used a variable delay inside the ping() function instead: > this seems to cause a lot less delay. A debug message can be used to notify the user if the > watchdog is trying to be kicked too quickly -- that would be more preferable than just shutting > the PMIC down and still provide a notification that something wasn't quite right. > > > > > Would this be possible ? > > I'll run the tests overnight. > I'm going to do something like this: > > diff --git a/linux-next/v4.0/drivers/watchdog/da9062_wdt.c b/linux-next/v4.0/drivers/watchdog/da9062_wdt.c > index ad80261..d596910 100644 > --- a/gp_sparse/linux-next/v4.0/drivers/watchdog/da9062_wdt.c > +++ b/gp_sparse/linux-next/v4.0/drivers/watchdog/da9062_wdt.c > > @@ -32,12 +33,37 @@ static const unsigned int wdt_timeout[] = { 0, 2, 4, 8, 16, 32, 65, 131 }; > #define DA9062_WDT_MIN_TIMEOUT wdt_timeout[DA9062_TWDSCALE_MIN] > #define DA9062_WDT_MAX_TIMEOUT wdt_timeout[DA9062_TWDSCALE_MAX] > #define DA9062_WDG_DEFAULT_TIMEOUT wdt_timeout[DA9062_TWDSCALE_MAX-1] > +#define DA9062_RESET_PROTECTION_MS 300 > > struct da9062_watchdog { > struct da9062 *hw; > struct watchdog_device wdtdev; > + unsigned long j_time_stamp; > }; > > +static void da9062_set_window_start(struct da9062_watchdog *wdt) > +{ > + wdt->j_time_stamp = jiffies; > +} > + > +static void da9062_apply_window_protection(struct da9062_watchdog *wdt) > +{ > + unsigned long delay = msecs_to_jiffies(DA9062_RESET_PROTECTION_MS); > + unsigned long timeout = wdt->j_time_stamp + delay; > + unsigned long now = jiffies; > + unsigned int diff_ms; > + > + /* if time-limit has not elapsed then wait for remainder */ > + if (time_before(now, timeout)) { > + diff_ms = jiffies_to_msecs(timeout-now); > + dev_dbg(wdt->hw->dev, > + "Delaying watchdog ping by %u msecs\n", diff_ms); I would not bother about the dev_dbg, but that is your call. > + mdelay(diff_ms); Can you use usleep_range() ? Othewise looks good. BTW, I had to do something similar in drivers/hwmon/pmbus/zl6100.c; this is where the idea comes from. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/