On Thu, 2015-06-18 at 18:19 +0800, YH Huang wrote: > On Fri, 2015-06-12 at 12:20 +0200, Thierry Reding wrote: > > > +/* Shift log2(PWM_PERIOD_MAX + 1) as divisor */ > > > +#define PWM_PERIOD_BIT_SHIFT 12 > > > > I wasn't very clear about this in my earlier review, so let me try to > > explain why I think this is confusing. You use this as a divisor, but > > you encode it as a shift. It's also PWM_PERIOD_MAX + 1, so I think it > > would make more sense to drop this, keep PWM_PERIOD_MAX as above and > > then replace the > > > > >> PWM_PERIOD_BIT_SHIFT > > > > below by > > > > / (PWM_PERIOD_MAX + 1) > > > > Maybe I can change in this way: > Remove this: #define PWM_PERIOD_MAX 0x00000fff > Using ">> PWM_PERIOD_BIT_SHIFT" is faster than "/ (PWM_PERIOD_MAX + 1)" > Is this right? The place which use this shift is: clk_div = div_u64(rate * period_ns, NSEC_PER_SEC) >> PWM_PERIOD_BIT_SHIFT; div_u64 return u64. If we change >> to /, and somehow compiler didn't optimize that div into shift, it will cause build error. Joe.C -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
