On Mon, Jan 22, 2018 at 10:49 AM, Greentime Hu [off-list ref] wrote:

2018-01-20 0:41 GMT+08:00 Arnd Bergmann [off-list ref]:

quoted

quoted

This implementation is referenced from openrisc.
https://lkml.org/lkml/2017/11/17/228

It's correct on openrisc, because that has a reliable cycle counter,
and that gets used in its delay function:

void __delay(unsigned long cycles)
{
        cycles_t start = get_cycles();
        while ((get_cycles() - start) < cycles)
                cpu_relax();
}

In my review comment that you cited, I assumed that nds32 had similar
hardware.

However, as you explained earlier, the nds32 architecture does not provide
a cycle counter and the clocksource resolution is not high enough to
be a good replacement, so you have to use the traditional delay
calibration.

Hi, Arnd:

Thank you for your explanation.
Will it be ok if I code it like this?

config GENERIC_CALIBRATE_DELAY
       def_bool y

Yes, I think that should be sufficient.

       Arnd