linux-kernel - Re: [PATCH 0/3] Suspending i.MX watchdog in WAIT mode

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Date:   Wed, 19 Oct 2022 08:30:54 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrej Picej <andrej.picej@...ik.com>
Cc:     linux-watchdog@...r.kernel.org, shawnguo@...nel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-imx@....com, festevam@...il.com,
        kernel@...gutronix.de, s.hauer@...gutronix.de,
        wim@...ux-watchdog.org, robh+dt@...nel.org
Subject: Re: [PATCH 0/3] Suspending i.MX watchdog in WAIT mode

On Wed, Oct 19, 2022 at 01:17:11PM +0200, Andrej Picej wrote:
> The i.MX6 watchdog can't be stopped once started. This means that
> special hardware suspend needs to be configured when the device enters
> low-power modes.
> Usually i.MX devices have two bits which deal with this:
> - WDZST bit disables the timer in "deeper" low power modes and
> - WDW bit disables the timer in "WAIT" mode which corresponds with
> Linux's "freeze" low-power mode.
> 
> WDZST bit support is already in place since 1a9c5efa576e ("watchdog: imx2_wdt: disable watchdog timer during low power mode").
> WDW bit is not common for all imx2-wdt supported devices, therefore use
> a new device-tree property "fsl,suspend-in-wait" which suspends the
> watchdog in "WAIT" mode.

I think that needs to be validated using the "compatible" property;
it should not be possible to set/accept the new flag for devices
which don't support it.

Thanks,
Guenter

> 
> Andrej Picej (3):
>   watchdog: imx2_wdg: suspend watchdog in WAIT mode
>   dt-bindings: watchdog: fsl-imx: document suspend in wait mode
>   ARM: dts: imx6ul/ull: suspend i.MX6UL watchdog in wait mode
> 
>  .../devicetree/bindings/watchdog/fsl-imx-wdt.yaml          | 5 +++++
>  arch/arm/boot/dts/imx6ul-phytec-phycore-som.dtsi           | 4 ++++
>  drivers/watchdog/imx2_wdt.c                                | 7 +++++++
>  3 files changed, 16 insertions(+)
> 
> -- 
> 2.25.1
>