Missing ARM TWD Watchdog driver?

Missing ARM TWD Watchdog driver?

[Boris Lysov]

Hello everyone,

I stumbled upon the ARM TWD Watchdog driver which seems to be missing (or I'm
just blind).

As per commit a33f5c380c4bd3fa5278d690421b72052456d9fe ("Merge tag
'xfs-5.17-merge-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux"), multiple
device trees declare usage of arm-twd:

arch/arm/boot/dts/arm-realview-eb-mp.dtsi
arch/arm/boot/dts/arm-realview-pb11mp.dts
arch/arm/boot/dts/arm-realview-pbx-a9.dts
arch/arm/boot/dts/bcm5301x.dtsi
arch/arm/boot/dts/bcm63138.dtsi
arch/arm/boot/dts/bcm-hr2.dtsi
arch/arm/boot/dts/bcm-nsp.dtsi
arch/arm/boot/dts/berlin2cd.dtsi
arch/arm/boot/dts/highbank.dts
arch/arm/boot/dts/mmp3.dtsi
arch/arm/boot/dts/owl-s500.dtsi
arch/arm/boot/dts/spear13xx.dtsi
arch/arm/boot/dts/ste-dbx5x0.dtsi
arch/arm/boot/dts/vexpress-v2p-ca5s.dts
arch/arm/boot/dts/vexpress-v2p-ca9.dts

and it is documented in
Documentation/devicetree/bindings/watchdog/arm,twd-wdt.yaml

However I could not find the driver itself. I tried running case-insensitive
grep and ripgrep to no avail. Does this driver actually exist? Is it gone?

I'm not well experienced with LKML yet and I apologize for if I asked
the question on the inappropriate mailing list. As per 3.3 of [1], I'm kindly
asking to CC me with answers.

Thanks!

[1] The linux-kernel mailing list FAQ http://vger.kernel.org/lkml/

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Re: Missing ARM TWD Watchdog driver?

[Guenter Roeck]

On 1/17/22 8:01 AM, Boris Lysov wrote:
> Hello everyone,
> 
> I stumbled upon the ARM TWD Watchdog driver which seems to be missing (or I'm
> just blind).
> 
> As per commit a33f5c380c4bd3fa5278d690421b72052456d9fe ("Merge tag
> 'xfs-5.17-merge-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux"), multiple
> device trees declare usage of arm-twd:
> 
> arch/arm/boot/dts/arm-realview-eb-mp.dtsi
> arch/arm/boot/dts/arm-realview-pb11mp.dts
> arch/arm/boot/dts/arm-realview-pbx-a9.dts
> arch/arm/boot/dts/bcm5301x.dtsi
> arch/arm/boot/dts/bcm63138.dtsi
> arch/arm/boot/dts/bcm-hr2.dtsi
> arch/arm/boot/dts/bcm-nsp.dtsi
> arch/arm/boot/dts/berlin2cd.dtsi
> arch/arm/boot/dts/highbank.dts
> arch/arm/boot/dts/mmp3.dtsi
> arch/arm/boot/dts/owl-s500.dtsi
> arch/arm/boot/dts/spear13xx.dtsi
> arch/arm/boot/dts/ste-dbx5x0.dtsi
> arch/arm/boot/dts/vexpress-v2p-ca5s.dts
> arch/arm/boot/dts/vexpress-v2p-ca9.dts
> 
> and it is documented in
> Documentation/devicetree/bindings/watchdog/arm,twd-wdt.yaml
> 
> However I could not find the driver itself. I tried running case-insensitive
> grep and ripgrep to no avail. Does this driver actually exist? Is it gone?
> 

I may be missing it, but I do not see any evidence that it ever existed.

Guenter

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Re: Missing ARM TWD Watchdog driver?

[Mark Rutland]

On Mon, Jan 17, 2022 at 08:34:57AM -0800, Guenter Roeck wrote:
> On 1/17/22 8:01 AM, Boris Lysov wrote:
> > Hello everyone,
> > 
> > I stumbled upon the ARM TWD Watchdog driver which seems to be missing (or I'm
> > just blind).
> > 
> > As per commit a33f5c380c4bd3fa5278d690421b72052456d9fe ("Merge tag
> > 'xfs-5.17-merge-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux"), multiple
> > device trees declare usage of arm-twd:
> > 
> > arch/arm/boot/dts/arm-realview-eb-mp.dtsi
> > arch/arm/boot/dts/arm-realview-pb11mp.dts
> > arch/arm/boot/dts/arm-realview-pbx-a9.dts
> > arch/arm/boot/dts/bcm5301x.dtsi
> > arch/arm/boot/dts/bcm63138.dtsi
> > arch/arm/boot/dts/bcm-hr2.dtsi
> > arch/arm/boot/dts/bcm-nsp.dtsi
> > arch/arm/boot/dts/berlin2cd.dtsi
> > arch/arm/boot/dts/highbank.dts
> > arch/arm/boot/dts/mmp3.dtsi
> > arch/arm/boot/dts/owl-s500.dtsi
> > arch/arm/boot/dts/spear13xx.dtsi
> > arch/arm/boot/dts/ste-dbx5x0.dtsi
> > arch/arm/boot/dts/vexpress-v2p-ca5s.dts
> > arch/arm/boot/dts/vexpress-v2p-ca9.dts
> > 
> > and it is documented in
> > Documentation/devicetree/bindings/watchdog/arm,twd-wdt.yaml
> > 
> > However I could not find the driver itself. I tried running case-insensitive
> > grep and ripgrep to no avail. Does this driver actually exist? Is it gone?
> > 
> 
> I may be missing it, but I do not see any evidence that it ever existed.

Likewise, AFAICT we added the binding but never the driver.

Looking at the git history, that schema was introduced in commit:

  50e02e9a030a9ae3 ("dt-bindings: timer: arm,twd: Convert to json-schema")

... and replaced Documentation/devicetree/bindings/timer/arm,twd.txt

Per:

  $ git log --follow Documentation/devicetree/bindings/timer/arm,twd.txt

That was introduced alongside a driver in commit:

  d8e0364364d333fe ("ARM: smp_twd: add device tree support")

... which only introduced a driver for the timer, and not the watchdog,
as the commit message notes.

Thanks.
Mark.

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Re: Missing ARM TWD Watchdog driver?

[Boris Lysov]

Hi Mark and Guenter,

On Mon, 17 Jan 2022 17:02:25 +0000,
Mark Rutland <mark.rutland@arm.com> wrote:

> On Mon, Jan 17, 2022 at 08:34:57AM -0800, Guenter Roeck wrote:
> > On 1/17/22 8:01 AM, Boris Lysov wrote:
> > > Hello everyone,
> > > 
> > > I stumbled upon the ARM TWD Watchdog driver which seems to be missing (or
> > > I'm just blind).
> > > 
> > > As per commit a33f5c380c4bd3fa5278d690421b72052456d9fe ("Merge tag
> > > 'xfs-5.17-merge-3' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux"),
> > > multiple device trees declare usage of arm-twd:
> > > 
> > > (...)
> > > 
> > > and it is documented in
> > > Documentation/devicetree/bindings/watchdog/arm,twd-wdt.yaml
> > > 
> > > However I could not find the driver itself. I tried running
> > > case-insensitive grep and ripgrep to no avail. Does this driver actually
> > > exist? Is it gone?
> > > 
> > 
> > I may be missing it, but I do not see any evidence that it ever existed.
> 
> Likewise, AFAICT we added the binding but never the driver.
> 
> Looking at the git history, that schema was introduced in commit:
> 
>   50e02e9a030a9ae3 ("dt-bindings: timer: arm,twd: Convert to json-schema")
> 
> ... and replaced Documentation/devicetree/bindings/timer/arm,twd.txt
> 
> Per:
> 
>   $ git log --follow Documentation/devicetree/bindings/timer/arm,twd.txt
> 
> That was introduced alongside a driver in commit:
> 
>   d8e0364364d333fe ("ARM: smp_twd: add device tree support")
> 
> ... which only introduced a driver for the timer, and not the watchdog,
> as the commit message notes.
> 
> Thanks.
> Mark.

Now I understand there's no ARM TWD Watchdog driver.
TYVM for your replies!

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