Re: [PATCH edk2-platforms] [PATCH v3 2/9] Platform/NXP : Add support for Watchdog driver

[Leif Lindholm <leif.lindholm@linaro.org>]

On Tue, Dec 05, 2017 at 05:07:00AM +0000, Udit Kumar wrote:
> >   I suggest return EFI_UNSUPPORTED for this case. The protocol implementation
> > could return its status besides spec defined status.
> 
> Thanks to help me , how core will treat this error  
> 1/  Wdt not available 
> 2/ ignoring this error 
> 3/ core is not registering handler  
> I guess 3 is valid, 

Looking at Core/Dxe/Misc/SetWatchdogTimer.c:
  //
  // Attempt to set the timeout
  //
  Status = gWatchdogTimer->SetTimerPeriod (gWatchdogTimer,
  MultU64x32 (Timeout, WATCHDOG_TIMER_CALIBRATE_PER_SECOND));

  //
  // Check for errors
  //
  if (EFI_ERROR (Status)) {
    return EFI_DEVICE_ERROR;
  }

The SetWatchdogTimer() call would always return EFI_DEVICE_ERROR.

> On side track, looks wdt is not used by core services then do we
> really need this as part of arch protocol ?

Yes, that was ultimately what I was implying with my question
regarding whether this protocol is relevant for a watchdog that can
only ever reset the system on timeout.

The protocol looks to me to be designed to use a dedicated generic
timer as backing for a software watchdog.

Liming, Mike?

If that is the case, then I agree this driver should probably not
implement this protocol, but rather set up a timer event (or a
dedicated timer) to stroke the watchdog.

Regards,

Leif

> regards
> Udit 
> 
> > -----Original Message-----
> > From: Gao, Liming [mailto:liming.gao@intel.com]
> > Sent: Monday, December 04, 2017 8:53 PM
> > To: Leif Lindholm <leif.lindholm@linaro.org>; Kinney, Michael D
> > <michael.d.kinney@intel.com>
> > Cc: Meenakshi Aggarwal <meenakshi.aggarwal@nxp.com>;
> > ard.biesheuvel@linaro.org; edk2-devel@lists.01.org; Udit Kumar
> > <udit.kumar@nxp.com>; Varun Sethi <V.Sethi@nxp.com>
> > Subject: RE: [PATCH edk2-platforms] [PATCH v3 2/9] Platform/NXP : Add support
> > for Watchdog driver
> > 
> > Leif:
> >   I suggest return EFI_UNSUPPORTED for this case. The protocol implementation
> > could return its status besides spec defined status.
> > 
> > Thanks
> > Liming
> > > -----Original Message-----
> > > From: Leif Lindholm [mailto:leif.lindholm@linaro.org]
> > > Sent: Monday, December 4, 2017 10:36 PM
> > > To: Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming
> > > <liming.gao@intel.com>
> > > Cc: Meenakshi Aggarwal <meenakshi.aggarwal@nxp.com>;
> > > ard.biesheuvel@linaro.org; edk2-devel@lists.01.org;
> > > udit.kumar@nxp.com; v.sethi@nxp.com
> > > Subject: Re: [PATCH edk2-platforms] [PATCH v3 2/9] Platform/NXP : Add
> > > support for Watchdog driver
> > >
> > > Mike, Liming, as MdePkg mainteiners - one question below:
> > >
> > > On Mon, Nov 27, 2017 at 04:21:50PM +0530, Meenakshi Aggarwal wrote:
> > > > diff --git a/Platform/NXP/Drivers/WatchDog/WatchDog.c
> > > > b/Platform/NXP/Drivers/WatchDog/WatchDog.c
> > > > new file mode 100644
> > > > index 0000000..a9c70ef
> > > > --- /dev/null
> > > > +++ b/Platform/NXP/Drivers/WatchDog/WatchDog.c
> > > > @@ -0,0 +1,421 @@
> > >
> > > ...
> > >
> > > > +/**
> > > > +  This function registers the handler NotifyFunction so it is
> > > > +called every time
> > > > +  the watchdog timer expires.  It also passes the amount of time
> > > > +since the last
> > > > +  handler call to the NotifyFunction.
> > > > +  If NotifyFunction is not NULL and a handler is not already
> > > > +registered,
> > > > +  then the new handler is registered and EFI_SUCCESS is returned.
> > > > +  If NotifyFunction is NULL, and a handler is already registered,
> > > > +  then that handler is unregistered.
> > > > +  If an attempt is made to register a handler when a handler is
> > > > +already registered,
> > > > +  then EFI_ALREADY_STARTED is returned.
> > > > +  If an attempt is made to unregister a handler when a handler is
> > > > +not registered,
> > > > +  then EFI_INVALID_PARAMETER is returned.
> > > > +
> > > > +  @param  This             The EFI_TIMER_ARCH_PROTOCOL instance.
> > > > +  @param  NotifyFunction   The function to call when a timer interrupt fires.
> > This
> > > > +                           function executes at TPL_HIGH_LEVEL. The DXE Core will
> > > > +                           register a handler for the timer interrupt, so it can know
> > > > +                           how much time has passed. This information is used to
> > > > +                           signal timer based events. NULL will unregister the handler.
> > > > +
> > > > +  @retval EFI_SUCCESS           The watchdog timer handler was registered.
> > > > +  @retval EFI_ALREADY_STARTED   NotifyFunction is not NULL, and a
> > handler is already
> > > > +                                registered.
> > > > +  @retval EFI_INVALID_PARAMETER NotifyFunction is NULL, and a handler
> > was not
> > > > +                                previously registered.
> > > > +
> > > > +**/
> > > > +STATIC
> > > > +EFI_STATUS
> > > > +EFIAPI
> > > > +WdogRegisterHandler (
> > > > +  IN EFI_WATCHDOG_TIMER_ARCH_PROTOCOL   *This,
> > > > +  IN EFI_WATCHDOG_TIMER_NOTIFY          NotifyFunction
> > > > +  )
> > > > +{
> > > > +  // ERROR: This function is not supported.
> > > > +  // The hardware watchdog will reset the board
> > > > +  return EFI_INVALID_PARAMETER;
> > >
> > > Michael, Liming - what's your take on this?
> > >
> > > Is EFI_WATCHDOG_TIMER_ARCH_PROTOCOL suitable for use with a pure-hw
> > > watchdog such as this?
> > >
> > > If so, what would be a suitable return code here?
> > > EFI_INVALID_PARAMETER does not look ideal.
> > >
> > > /
> > >     Leif