Thanks for note Leif,
I am trying to understand this behavior of specification.
>"If no handler has been registered, or the registered handler returns, then
>the system will be reset by calling the Runtime Service ResetSystem()."
I believe, this handler needs to be called by wdt driver after wdt is expired.
Meaning , we want wdt to work without resetting the system.
Therefore a mask is needed with wdt, which will prevent to reset the system.
I see it working, at least for SP805, because of PMU mask bits.
Also ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c has this limitation.
I haven’t read spec of this wdt. I hope there should a mask around.
Coming back to hardware, which does not have mask around wdt, how to implement
this feature.
Regards
Udit
From: Leif Lindholm <leif.lindh...@linaro.org>
Sent: Monday, December 17, 2018 6:25 PM
To: Sami Mujawar <sami.muja...@arm.com>; Thomas Panakamattam Abraham
<thomas.abra...@arm.com>
Cc: Meenakshi Aggarwal <meenakshi.aggar...@nxp.com>; Udit Kumar
<udit.ku...@nxp.com>; Ard Biesheuvel <ard.biesheu...@linaro.org>; edk2-devel
(edk2-devel@lists.01.org) <edk2-devel@lists.01.org>; Ming Huang
<ming.hu...@linaro.org>; Heyi Guo <heyi....@linaro.org>; Matteo Carlini
<matteo.carl...@arm.com>; Nariman Poushin <nariman.pous...@linaro.org>
Subject: SP805 driver
Hi Sami, Thomas, (and others on cc)
NXP are upstreaming a set containing an implementation of
EFI_WATCHDOG_TIMER_ARCH_PROTOCOL using a hardware watchdog as backing.
This idea comes from the SP805 driver ArmPlatformPkg/Drivers/SP805WatchdogDxe,
which does the same.
The problem is that this is a horrible idea. The point of the
EFI_WATCHDOG_TIMER_ARCH_PROTOCOL is that it lets you schedule software events
when the watchdog timer expires. However, the SP805 driver does not let you do
this:
EFI_STATUS
EFIAPI
SP805RegisterHandler (
IN CONST 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;
}
From section 12.14 of the PI 1.6 spec:
"If no handler has been registered, or the registered handler returns, then the
system will be reset by calling the Runtime Service ResetSystem()."
Blatantly, any driver that does the above (and initializes hardware that will
reset the system without software control) will violate this.
Meanwhile, the only two ARM platforms that include this driver are TC2 and FVP.
Now, NXP are not at fault for following examples given to them in the reference
ARM driver section - but can we please keep further people from making the same
mistake?
So my question to {Sami|Thomas} is - can we nuke this driver, and if so, can
you provide the patches to remove it from edk2 and the resulting ones needed
for edk2-platforms?
I have no issues with reintroducing a fixed SP805 driver in the future that
does not claim to conform to the above protocol.
Finally - both the D03 and D05 platform .dsc files, as well as the Hisilicon
ArmPlatformLib, contain references to it. (Ming/Heyi - please provide a patch.)
/
Leif
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