On 7/10/19 12:07 AM, Guenter Roeck wrote:
> Ah, we are talking about the _smallest_ timeout and about resolution.
> But that is no reason to declare the clock invalid. Just set the minimum
> to the actual minimum. There is no reason to reject slow clocks entirely,
> even if the granularity is in the multi-second range. The only caveat,
> if granularity is more than one second, is that the set_timeout function
> must select and report the actual timeout.
I did consider supporting slower clocks but thought that the required
additional logic was perhaps not worth it. So instead just declared
those clock frequencies invalid.
However, if that logic is required, sure I can try to implement it.
It might take some weeks before I have time to look at it properly.
Thanks,
Tomas
>
> Thanks,
> Guenter
>
>> Thanks,
>>
>> Tomas
>>
>>>> Signed-off-by: Tomas Melin <tomas.melin@xxxxxxxxxxx>
>>>> ---
>>>> drivers/watchdog/cadence_wdt.c | 21 +++++++++++++++------
>>>> 1 file changed, 15 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/watchdog/cadence_wdt.c b/drivers/watchdog/cadence_wdt.c
>>>> index 0bdb275d904a..037faf557f9d 100644
>>>> --- a/drivers/watchdog/cadence_wdt.c
>>>> +++ b/drivers/watchdog/cadence_wdt.c
>>>> @@ -33,16 +33,17 @@
>>>> #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000
>>>>
>>>> /* Clock prescaler value and selection */
>>>> +#define CDNS_WDT_PRESCALE_8 8
>>>> #define CDNS_WDT_PRESCALE_64 64
>>>> #define CDNS_WDT_PRESCALE_512 512
>>>> #define CDNS_WDT_PRESCALE_4096 4096
>>>> +#define CDNS_WDT_PRESCALE_SELECT_8 0
>>>> #define CDNS_WDT_PRESCALE_SELECT_64 1
>>>> #define CDNS_WDT_PRESCALE_SELECT_512 2
>>>> #define CDNS_WDT_PRESCALE_SELECT_4096 3
>>>>
>>>> -/* Input clock frequency */
>>>> -#define CDNS_WDT_CLK_10MHZ 10000000
>>>> -#define CDNS_WDT_CLK_75MHZ 75000000
>>>> +/* Base input clock frequency */
>>>> +#define CDNS_WDT_CLK_32KHZ 32768
>>> ^ Please use a tab here
>>>
>>>>
>>>> /* Counter maximum value */
>>>> #define CDNS_WDT_COUNTER_MAX 0xFFF
>>>> @@ -318,10 +319,18 @@ static int cdns_wdt_probe(struct platform_device *pdev)
>>>> return ret;
>>>>
>>>> clock_f = clk_get_rate(wdt->clk);
>>>> - if (clock_f == 0) {
>>>> - dev_err(dev, "invalid clock frequency, (f=%lu)\n", clock_f);
>>>> + if (clock_f < CDNS_WDT_CLK_32KHZ) {
>>>> + dev_err(dev,
>>>> + "cannot find suitable clock prescaler, (f=%lu)\n",
>>>> + clock_f);
>>>> return -EINVAL;
>>>> - } else if (clock_f <= CDNS_WDT_CLK_75MHZ) {
>>>> + } else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_8) {
>>>> + wdt->prescaler = CDNS_WDT_PRESCALE_8;
>>>> + wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_8;
>>>> + } else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_64) {
>>>> + wdt->prescaler = CDNS_WDT_PRESCALE_64;
>>>> + wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_64;
>>>> + } else if (clock_f <= CDNS_WDT_CLK_32KHZ * CDNS_WDT_PRESCALE_512) {
>>>> wdt->prescaler = CDNS_WDT_PRESCALE_512;
>>>> wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
>>>> } else {
>>>> --
>>>> 2.17.2
>>>>
