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mmc: sdhci-s3c: Use shifts to divide by powers of two

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Current implementation of sdhci_s3c_consider_clock() is highly
inefficient due to multiple integer divisions by variable performed in a
loop. Since only divisors that are powers of two are considered, this
patch replaces them with respective shifts, removing all the integer
divisions.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by; Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <chris@printf.net>
This commit is contained in:
Tomasz Figa 2014-01-11 22:39:01 +01:00 committed by Chris Ball
parent d9c3f5df53
commit 8880a4a526
1 changed files with 5 additions and 5 deletions
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10
drivers/mmc/host/sdhci-s3c.c
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@ -144,7 +144,7 @@ static unsigned int sdhci_s3c_consider_clock(struct sdhci_s3c *ourhost,
{
unsigned long rate;
struct clk *clksrc = ourhost->clk_bus[src];
int div;
int shift;
if (!clksrc)
return UINT_MAX;
@ -160,15 +160,15 @@ static unsigned int sdhci_s3c_consider_clock(struct sdhci_s3c *ourhost,
rate = clk_get_rate(clksrc);
for (div = 1; div < 256; div *= 2) {
if ((rate / div) <= wanted)
for (shift = 0; shift < 8; ++shift) {
if ((rate >> shift) <= wanted)
break;
}
dev_dbg(&ourhost->pdev->dev, "clk %d: rate %ld, want %d, got %ld\n",
src, rate, wanted, rate / div);
src, rate, wanted, rate >> shift);
return wanted - (rate / div);
return wanted - (rate >> shift);
}
/**