On 07/22, Andy Shevchenko wrote: > On Tue, 2015-07-21 at 17:41 -0700, Stephen Boyd wrote: > > On 07/14, Andy Shevchenko wrote: > > > diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk > > > -fractional-divider.c > > > index 7cfcc56..16f42ae 100644 > > > --- a/drivers/clk/clk-fractional-divider.c > > > +++ b/drivers/clk/clk-fractional-divider.c > > > @@ -128,9 +128,11 @@ struct clk > > > *clk_register_fractional_divider(struct device *dev, > > > > > > fd->reg = reg; > > > fd->mshift = mshift; > > > - fd->mmask = (BIT(mwidth) - 1) << mshift; > > > + fd->mwidth = mwidth; > > > + fd->mmask = GENMASK(mwidth - 1, 0) << mshift; > > > fd->nshift = nshift; > > > - fd->nmask = (BIT(nwidth) - 1) << nshift; > > > + fd->nwidth = nwidth; > > > + fd->nmask = GENMASK(nwidth - 1, 0) << nshift; > > > > Please do the shifts in the GENMASK. > > It's not optimal. Waste of performance. > > 32-bit case on 32-bit machine (similar to other cases on x86). > > a) GENMASK(x - 1, 0) << y > > movl $32, %ecx > subb 4(%esp), %cl > movl $-1, %eax > shrl %cl, %eax > movzbl 8(%esp), %ecx > sall %cl, %eax > ret > > b) GENMASK(x + y - 1, y) > > pushl %esi > pushl %ebx > movl $1, %edx > movzbl 12(%esp), %eax > movzbl 16(%esp), %esi > movl $-1, %ebx > subl %eax, %edx > movl %ebx, %eax > subl %esi, %edx > leal 31(%edx), %ecx > shrl %cl, %eax > movl %esi, %ecx > sall %cl, %ebx > andl %ebx, %eax > popl %ebx > popl %esi > ret >
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