On 07/07, Andy Shevchenko wrote: > On Thu, 2015-06-18 at 12:48 -0700, Stephen Boyd wrote: > > On 03/31, Andy Shevchenko wrote: > > > diff --git a/include/linux/clk-provider.h b/include/linux/clk > > > -provider.h > > > index 5591ea7..20b0b67 100644 > > > --- a/include/linux/clk-provider.h > > > +++ b/include/linux/clk-provider.h > > > @@ -353,6 +353,11 @@ struct clk_divider { > > > spinlock_t *lock; > > > }; > > > > > > +static inline unsigned long clk_div_mask(u8 width) > > > +{ > > > + return (1 << width) - 1; > > > +} > > > + > > > > Why not just change drivers to use GENMASK? It's a proven and > > tested way to generate a bitmask. > > Too many unneeded calculations I suppose.
That's what compiler optimizations are for. > > Compare: > mask = clk_div_mask(mm) << ms; > which is simple ((1 << mm) - 1) << ms > and > mask = GENMASK(mm + ms - 1, ms); > which is (~0 << ms) & (~0 >> (BITS_PER_LONG - 1 - (mm + ms - > 1))) And if mm is 32 then we hit undefined behavior. > > > > > So I'd rather see drivers converted to use that macro directly > > especially because the mask may need to start at some bit that > > isn't 0. > > If you think the above is not a burden, I can do the conversion to > GENMASK. > > Though it might make sense when ms = 0 explicitly. > Yes let's use GENMASK. I imagine the extra few instructions are negligible. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/