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i2c: rcar: get clock rate only once and simplify calculation

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There is no need to repeatedly query clock frequency, where it is not
expected to change. The complete loop can also trivially be replaced with
a simple division. A further loop below the one, being simplified, could
also be replaced, but that would get more complicated.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Guennadi Liakhovetski 2013-09-12 14:36:45 +02:00 committed by Wolfram Sang
parent 14d32f1794
commit 8d0494037b
1 changed files with 13 additions and 7 deletions
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20
drivers/i2c/busses/i2c-rcar.c
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@ -231,6 +231,7 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv,
u32 round, ick;
u32 scl;
u32 cdf_width;
unsigned long rate;
if (!clkp) {
dev_err(dev, "there is no peripheral_clk\n");
@ -264,15 +265,14 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv,
* clkp : peripheral_clk
* F[] : integer up-valuation
*/
for (cdf = 0; cdf < (1 << cdf_width); cdf++) {
ick = clk_get_rate(clkp) / (1 + cdf);
if (ick < 20000000)
goto ick_find;
rate = clk_get_rate(clkp);
cdf = rate / 20000000;
if (cdf >= 1 << cdf_width) {
dev_err(dev, "Input clock %lu too high\n", rate);
return -EIO;
}
dev_err(dev, "there is no best CDF\n");
return -EIO;
ick = rate / (cdf + 1);
ick_find:
/*
* it is impossible to calculate large scale
* number on u32. separate it
@ -290,6 +290,12 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv,
*
* Calculation result (= SCL) should be less than
* bus_speed for hardware safety
*
* We could use something along the lines of
* div = ick / (bus_speed + 1) + 1;
* scgd = (div - 20 - round + 7) / 8;
* scl = ick / (20 + (scgd * 8) + round);
* (not fully verified) but that would get pretty involved
*/
for (scgd = 0; scgd < 0x40; scgd++) {
scl = ick / (20 + (scgd * 8) + round);