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staging: sm750fb: refactor the clock frequency calculation method

PATCH In review Lynn Lei 2 participants 2 messages Jul 2, 2017 – Jul 3, 2017

Subsystems (3)
Staging Framebuffer layer Staging - silicon motion SM750 frame buffer driver
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Lynn Lei

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#0 lore raw

PATCH 1/1 staging: sm750fb: refactor the clock frequency calculation method

speed up calculation by merging two divisions into one.

Signed-off-by Lynn Lei <[email protected]>
---
 drivers/staging/sm750fb/ddk750_chip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/staging/sm750fb/ddk750_chip.c +1 -1
index c51761221131..5970c3792f27 100644
@@ -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));
 }
 
 /*
Signature · 1 line
2.13.2
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#1 lore raw
Quoted 1 line · Lynn Lei

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.

Quoted 11 lines
Signed-off-by Lynn Lei <[email protected]>
---
 drivers/staging/sm750fb/ddk750_chip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/staging/sm750fb/ddk750_chip.c +0 -0
index c51761221131..5970c3792f27 100644

drivers/staging/sm750fb/ddk750_chip.c static unsigned int get_mxclk_freq(void) · line 47

Quoted 5 lines
drivers/staging/sm750fb/ddk750_chip.c +1 -1
@@ -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