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 <[email protected]> --- drivers/i2c/busses/i2c-rcar.c | 20 +++++++++++++------- 1 files changed, 13 insertions(+), 7 deletions(-) diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 15eef94..9325db4 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -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 @@ ick_find: * * 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); -- 1.7.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
