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| author | Tomasz Figa <tomasz.figa@gmail.com> | 2014-01-11 22:39:01 +0100 |
|---|---|---|
| committer | Chris Ball <chris@printf.net> | 2014-03-03 10:21:32 -0500 |
| commit | 8880a4a526340335403696f30daf4e05a413f3bd (patch) | |
| tree | 7f83dbbb7f54132ae75d30bda5359ef3808f9107 | |
| parent | d9c3f5df539a8a74cc830b35838670fe0541fed1 (diff) | |
| download | linux-8880a4a526340335403696f30daf4e05a413f3bd.tar.gz | |
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>
| -rw-r--r-- | drivers/mmc/host/sdhci-s3c.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/mmc/host/sdhci-s3c.c b/drivers/mmc/host/sdhci-s3c.c index 6debda952155..52770d58cc47 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); } /** |