Messages in this thread | | | Subject | Re: [PATCH v4 3/6] clk: fractional-divider: keep mwidth and nwidth internally | From | Andy Shevchenko <> | Date | Wed, 22 Jul 2015 16:09:26 +0300 |
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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
-- Andy Shevchenko <andriy.shevchenko@linux.intel.com> Intel Finland Oy
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