linux-kernel - Re: [PATCH 2/4] mfd: lpc_ich: Do not create iTCO watchdog when WDAT table exists

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Date:   Wed, 14 Sep 2016 13:03:41 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, Jean Delvare <jdelvare@...e.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Peter Tyser <ptyser@...-inc.com>,
        Lee Jones <lee.jones@...aro.org>,
        Zha Qipeng <qipeng.zha@...el.com>,
        Darren Hart <dvhart@...radead.org>,
        Wim Van Sebroeck <wim@...ana.be>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] mfd: lpc_ich: Do not create iTCO watchdog when WDAT
 table exists

On Tue, Sep 13, 2016 at 06:23:34PM +0300, Mika Westerberg wrote:
> ACPI WDAT table is the preferred way to use hardware watchdog over the
> native iTCO_wdt. Windows only uses this table for its hardware watchdog
> implementation so we should be relatively safe to trust it has been
> validated by OEMs
> 
> Prevent iTCO watchdog creation if we detect that there is ACPI WDAT table.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>  drivers/mfd/lpc_ich.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mfd/lpc_ich.c b/drivers/mfd/lpc_ich.c
> index bd3aa4578346..c8dee47b45d9 100644
> --- a/drivers/mfd/lpc_ich.c
> +++ b/drivers/mfd/lpc_ich.c
> @@ -984,6 +984,10 @@ static int lpc_ich_init_wdt(struct pci_dev *dev)
>  	int ret;
>  	struct resource *res;
>  
> +	/* If we have ACPI based watchdog use that instead */
> +	if (acpi_has_watchdog())
> +		return -ENODEV;
> +
>  	/* Setup power management base register */
>  	pci_read_config_dword(dev, priv->abase, &base_addr_cfg);
>  	base_addr = base_addr_cfg & 0x0000ff80;
> -- 
> 2.9.3
>