Sender: Guenter Roeck <groeck7@gmail.com>
Subject: Re: [RFC PATCH] watchdog: da9062: Correct the timeout values
To:     Christoph Niedermaier <cniedermaier@dh-electronics.com>,
        linux-arm-kernel@lists.infradead.org
Cc:     Support Opensource <support.opensource@diasemi.com>,
        Adam Thomson <Adam.Thomson.Opensource@diasemi.com>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Andrej Picej <andrej.picej@norik.com>,
        linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20211203163539.91870-1-cniedermaier@dh-electronics.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <dc6a432c-79a3-881c-eac4-32620040d11b@roeck-us.net>
Date:   Fri, 3 Dec 2021 08:52:12 -0800
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On 12/3/21 8:35 AM, Christoph Niedermaier wrote:
> I measured the timeout values of my DA9061 chip. According to the
> information in the data sheet the formula should be:
> 
> timeout = 2.048 * 2^(regval - 1)
> 
> But my measured values differ from that.
> Accoring to my measured values the formula must be:
> 
> timeout = 3.2 * 2^(regval - 1)
> 
> Is there something wrong with my chip, or has anyone else noticed this as well?

The driver assumes a static and well defined clock rate. Maybe that rate
is different in your system (if that is possible) ?

Guenter

> 
> Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
> Cc: Support Opensource <support.opensource@diasemi.com>
> Cc: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
> Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
> Cc: Guenter Roeck <linux@roeck-us.net>
> Cc: Andrej Picej <andrej.picej@norik.com>
> Cc: linux-watchdog@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> To: linux-arm-kernel@lists.infradead.org
> ---
>   drivers/watchdog/da9062_wdt.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/da9062_wdt.c b/drivers/watchdog/da9062_wdt.c
> index f02cbd530538..d2576aba9ca5 100644
> --- a/drivers/watchdog/da9062_wdt.c
> +++ b/drivers/watchdog/da9062_wdt.c
> @@ -20,7 +20,8 @@
>   #include <linux/regmap.h>
>   #include <linux/of.h>
>   
> -static const unsigned int wdt_timeout[] = { 0, 2, 4, 8, 16, 32, 65, 131 };
> +static const unsigned int wdt_timeout[] = { 0, 3, 6, 12, 25, 51, 102, 204 };
> +
>   #define DA9062_TWDSCALE_DISABLE		0
>   #define DA9062_TWDSCALE_MIN		1
>   #define DA9062_TWDSCALE_MAX		(ARRAY_SIZE(wdt_timeout) - 1)
>