linux-kernel - Missing ARM TWD Watchdog driver?

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Date:   Mon, 17 Jan 2022 19:01:12 +0300
From:   Boris Lysov <arzamas-16@...l.ee>
To:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Missing ARM TWD Watchdog driver?

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/