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| Started by | Lynn Lei <lynnl.wit@gmail.com> |
|---|---|
| First post | 2017-07-02 14:30 +0200 |
| Last post | 2017-07-03 08:30 +0200 |
| Articles | 2 — 2 participants |
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[PATCH] staging: sm750fb: refactor the clock frequency calculation method Lynn Lei <lynnl.wit@gmail.com> - 2017-07-02 14:30 +0200
Re: [PATCH] staging: sm750fb: refactor the clock frequency calculation method Greg KH <gregkh@linuxfoundation.org> - 2017-07-03 08:30 +0200
| From | Lynn Lei <lynnl.wit@gmail.com> |
|---|---|
| Date | 2017-07-02 14:30 +0200 |
| Subject | [PATCH] staging: sm750fb: refactor the clock frequency calculation method |
| Message-ID | <tYMaJ-1MG-1@gated-at.bofh.it> |
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(-) 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)); } /* -- 2.13.2
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| From | Greg KH <gregkh@linuxfoundation.org> |
|---|---|
| Date | 2017-07-03 08:30 +0200 |
| Subject | Re: [PATCH] staging: sm750fb: refactor the clock frequency calculation method |
| Message-ID | <tZ31U-5Fr-21@gated-at.bofh.it> |
| In reply to | #1679450 |
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
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