| Message ID | 20170702122426.GA17561@lynnl.wit (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jul 02, 2017 at 08:24:26PM +0800, Lynn Lei wrote: > speed up calculation by merging two divisions into one. How much did you speed it up? Please provide proof of anything like this if you say it is a speed up. > > Signed-off-by: Lynn Lei <lynnl.wit@gmail.com> > --- > drivers/staging/sm750fb/ddk750_chip.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/staging/sm750fb/ddk750_chip.c b/drivers/staging/sm750fb/ddk750_chip.c > index c51761221131..5970c3792f27 100644 > --- a/drivers/staging/sm750fb/ddk750_chip.c > +++ b/drivers/staging/sm750fb/ddk750_chip.c > @@ -44,7 +44,7 @@ static unsigned int get_mxclk_freq(void) > OD = (pll_reg & PLL_CTRL_OD_MASK) >> PLL_CTRL_OD_SHIFT; > POD = (pll_reg & PLL_CTRL_POD_MASK) >> PLL_CTRL_POD_SHIFT; > > - return DEFAULT_INPUT_CLOCK * M / N / (1 << OD) / (1 << POD); > + return DEFAULT_INPUT_CLOCK * M / N / (1 << (OD + POD)); Are you sure that gcc didn't already do this for you? It's a constant number, I doubt this did anything at all. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/staging/sm750fb/ddk750_chip.c b/drivers/staging/sm750fb/ddk750_chip.c index c51761221131..5970c3792f27 100644 --- a/drivers/staging/sm750fb/ddk750_chip.c +++ b/drivers/staging/sm750fb/ddk750_chip.c @@ -44,7 +44,7 @@ static unsigned int get_mxclk_freq(void) OD = (pll_reg & PLL_CTRL_OD_MASK) >> PLL_CTRL_OD_SHIFT; POD = (pll_reg & PLL_CTRL_POD_MASK) >> PLL_CTRL_POD_SHIFT; - return DEFAULT_INPUT_CLOCK * M / N / (1 << OD) / (1 << POD); + return DEFAULT_INPUT_CLOCK * M / N / (1 << (OD + POD)); } /*
speed up calculation by merging two divisions into one. Signed-off-by: Lynn Lei <lynnl.wit@gmail.com> --- drivers/staging/sm750fb/ddk750_chip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)