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authorTomasz Figa <tomasz.figa@gmail.com>2014-01-11 22:39:01 +0100
committerChris Ball <chris@printf.net>2014-03-03 10:21:32 -0500
commit8880a4a526340335403696f30daf4e05a413f3bd (patch)
tree7f83dbbb7f54132ae75d30bda5359ef3808f9107 /drivers/mmc
parentd9c3f5df539a8a74cc830b35838670fe0541fed1 (diff)
mmc: sdhci-s3c: Use shifts to divide by powers of two
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>
Diffstat (limited to 'drivers/mmc')
-rw-r--r--drivers/mmc/host/sdhci-s3c.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c
index 6debda95215..52770d58cc4 100644
--- a/drivers/mmc/host/sdhci-s3c.c
+++ b/drivers/mmc/host/sdhci-s3c.c
@@ -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);
}
/**