rv_timer_approximate_tick_params bug

[Ho3eintaji]

@davideschiavone, I ran into a bug while using the timer in Heepocrates which probably the same story for xheep. The function "rv_timer_approximate_tick_params" which is used for setting prescale and step params based on CPU freq and desired timer freq is not working well and most of the times it returns 0 for these params

[davideschiavone]

I guess it is due to the time requested and frequency at which you are running - I am not familiar with the HAL of the timer, it is from OpenTitan - maybe you want to have a look there?

[Ho3eintaji]

Ok, I checked, it comes from Euclidean GCD used in the function. Actually, it happens when CLK_FREQ and desired TIMER_FREQ have small gcd (for example 1 !), it put large value for prescale (CLK_FREQ/ gcd) which is larger than what timer support so it returns 0 as not supported.

So should be either we change this function to be more approximate or be careful while putting clk and desired timer frequency.

[davideschiavone]

changing the function should be better in my opion

[JoseCalero]

@Ho3eintaji is this fixed then?

[Ho3eintaji]

No. atm, in my app, I check whether this happens or not:
rv_timer_approximate_tick_params(SYS_FREQ, TIMER_FREQ, &tick_params);
if (tick_params.prescale==0){
printf("Timer approximate function was not able to set a correct value prescale");
}

Later, I will change the function inside to prevent it