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SubjectRe: [PATCH v1 1/1] clk: fractional-divider: Move mask calculations out of lock
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Le 03/03/2024 à 13:14, Andy Shevchenko a écrit :
> There is no need to calculate masks under the lock taken.
> Move them out of it.
>
> Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> ---
> drivers/clk/clk-fractional-divider.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c
> index a0178182fc72..da057172cc90 100644
> --- a/drivers/clk/clk-fractional-divider.c
> +++ b/drivers/clk/clk-fractional-divider.c
> @@ -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;
> +

Hi,

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

CJ

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