linux-kernel - Re: [PATCH v2 3/4] clocksource/drivers/timer-vt8500: Add watchdog functionality

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Message-ID: <aCNLyYtxmqqklBN8@mai.linaro.org>
Date: Tue, 13 May 2025 15:40:25 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Alexey Charkov <alchark@...il.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 3/4] clocksource/drivers/timer-vt8500: Add watchdog
 functionality

On Wed, May 07, 2025 at 10:58:32AM +0400, Alexey Charkov wrote:
> VIA/WonderMedia system timer IP can generate a watchdog reset when its
> clocksource counter matches the value in the match register 0 and
> watchdog function is enabled. For this to work, obvously the clock event
> device must use a different match register (1~3) and respective interrupt.
> 
> Check if at least two interrupts are provided by the device tree, then use
> match register 1 for system clock events and match register 0 for watchdog
> respectively.

This code falls under the watchdog umbrella not in the clocksource. It
is better to find a way to make the timer and the watchdog separated.

The timer-gxp.c is dynamically allocating a watchdog platform device
with the shared pointer to the timer counter. IMO, it is a good
example to split this up.

> Signed-off-by: Alexey Charkov <alchark@...il.com>
> ---
>  drivers/clocksource/Kconfig        | 11 +++++++
>  drivers/clocksource/timer-vt8500.c | 61 ++++++++++++++++++++++++++++++++++----
>  2 files changed, 67 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 487c8525996724fbf9c6e9726dabb478d86513b9..8f5e41ff23386d9ecb46b38603dae485db71cfc7 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -181,6 +181,17 @@ config VT8500_TIMER
>  	help
>  	  Enables support for the VT8500 driver.
>  
> +config VT8500_TIMER_WATCHDOG
> +	bool "Enable VT8500 watchdog functionality"
> +	depends on VT8500_TIMER
> +	depends on WATCHDOG && WATCHDOG_CORE=y

if WATCHDOG_CORE=y then WATCHDOG=y because the first one can be
enabled only if the second one is enabled.

[ ... ]

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