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@xxxxxxxxx>
---
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
--
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