lkml.org 
[lkml]   [2024]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v1 1/1] clk: fractional-divider: Move mask calculations out of lock
On Sat, Mar 9, 2024 at 9:19 AM Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
> Le 03/03/2024 à 13:14, Andy Shevchenko a écrit :

..

> > @@ -195,14 +195,14 @@ static int clk_fd_set_rate(struct clk_hw *hw, unsigned long rate,
> > n--;
> > }
> >
> > + mmask = GENMASK(fd->mwidth - 1, 0) << fd->mshift;
> > + nmask = GENMASK(fd->nwidth - 1, 0) << fd->nshift;

> if this is a hot path, you could maybe even compute:

It's not. set_rate() may be called only on disabled (and unprepared?)
clocks, which makes it already a too slow operation.

> mask = ~(GENMASK(fd->mwidth - 1, 0) << fd->mshift |
> GENMASK(fd->nwidth - 1, 0) << fd->nshift)
>
> unless gcc is smart enough to do it by itself.
>
> > if (fd->lock)
> > spin_lock_irqsave(fd->lock, flags);
> > else
> > __acquire(fd->lock);
> >
> > - mmask = GENMASK(fd->mwidth - 1, 0) << fd->mshift;
> > - nmask = GENMASK(fd->nwidth - 1, 0) << fd->nshift;
> > -
> > val = clk_fd_readl(fd);
> > val &= ~(mmask | nmask);
>
> val &= mask;
>
> > val |= (m << fd->mshift) | (n << fd->nshift);
>
> and pre-compute "(m << fd->mshift) | (n << fd->nshift)" outside of the
> lock too.

All of these sound to me as premature optimisations. I only wanted to
get back to the status quo.

--
With Best Regards,
Andy Shevchenko

\
 
 \ /
  Last update: 2024-05-27 15:43    [W:0.106 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site