Re: [PATCH v2 2/4] watchdog: cadence_wdt: Calculate actual timeout limits

[Guenter Roeck <linux@roeck-us.net>]

On Fri, Jul 05, 2019 at 11:46:02AM +0000, Melin Tomas wrote:
> Maximum and minimum timeout values depend on the actual input clock
> frequency and prescaler selection.
> 
> Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
> ---
>  drivers/watchdog/cadence_wdt.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
> index 415bd6dd1edb..87b767c87bb6 100644
> --- a/drivers/watchdog/cadence_wdt.c
> +++ b/drivers/watchdog/cadence_wdt.c
> @@ -18,9 +18,6 @@
>  #include <linux/watchdog.h>
>  
>  #define CDNS_WDT_DEFAULT_TIMEOUT	10
> -/* Supports 1 - 516 sec */
> -#define CDNS_WDT_MIN_TIMEOUT	1
> -#define CDNS_WDT_MAX_TIMEOUT	516
>  
>  /* Restart key */
>  #define CDNS_WDT_RESTART_KEY 0x00001999
> @@ -28,6 +25,10 @@
>  /* Counter register access key */
>  #define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000
>  
> +/* Counter control register, counter restart values */
> +#define CDNS_WDT_CCR_CRV_MIN 0xFFF
> +#define CDNS_WDT_CCR_CRV_MAX 0xFFFFFF
> +
>  /* Counter value divisor */
>  #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
>  
> @@ -315,8 +316,10 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>  	cdns_wdt_device->info = &cdns_wdt_info;
>  	cdns_wdt_device->ops = &cdns_wdt_ops;
>  	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
> -	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
> -	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;
> +	cdns_wdt_device->min_timeout =
> +		CDNS_WDT_CCR_CRV_MIN * wdt->prescaler / clock_f;
> +	cdns_wdt_device->max_timeout =
> +		CDNS_WDT_CCR_CRV_MAX * wdt->prescaler / clock_f;

clock_f can at least in theory be 0. So far that didn't matter as
much, but now it would crash the kernel. Please add a respective
check into the code.

>  
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	wdt->regs = devm_ioremap_resource(&pdev->dev, res);