On Wed, Jul 10, 2019 at 07:20:59PM +0000, Melin Tomas wrote:
>
> 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.
>
Hmm ... not sure I understand. What makes it so difficult ?
Guenter
> 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
> >>>>
