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i2c: rcar: honor additional i2c timings from DT

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Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Wolfram Sang 2015-12-08 10:37:49 +01:00 committed by Wolfram Sang
parent c7881871de
commit ca68eade66
2 changed files with 16 additions and 9 deletions
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4
Documentation/devicetree/bindings/i2c/i2c-rcar.txt
View File

@ -20,6 +20,10 @@ Optional properties:
propoerty indicates the default frequency 100 kHz.
- clocks: clock specifier.
- i2c-scl-falling-time-ns: see i2c.txt
- i2c-scl-internal-delay-ns: see i2c.txt
- i2c-scl-rising-time-ns: see i2c.txt
Examples :
i2c0: i2c@e6508000 {

21
drivers/i2c/busses/i2c-rcar.c
View File

@ -164,12 +164,15 @@ static int rcar_i2c_bus_barrier(struct rcar_i2c_priv *priv)
static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv, struct i2c_timings *t)
{
u32 scgd, cdf, round, ick, scl, cdf_width;
u32 scgd, cdf, round, ick, sum, scl, cdf_width;
unsigned long rate;
struct device *dev = rcar_i2c_priv_to_dev(priv);
/* Fall back to previously used values if not supplied */
t->bus_freq_hz = t->bus_freq_hz ?: 100000;
t->scl_fall_ns = t->scl_fall_ns ?: 35;
t->scl_rise_ns = t->scl_rise_ns ?: 200;
t->scl_int_delay_ns = t->scl_int_delay_ns ?: 50;
switch (priv->devtype) {
case I2C_RCAR_GEN1:
@ -193,9 +196,9 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv, struct i2c_timin
* SCL = ick / (20 + SCGD * 8 + F[(ticf + tr + intd) * ick])
*
* ick : I2C internal clock < 20 MHz
* ticf : I2C SCL falling time = 35 ns here
* tr : I2C SCL rising time = 200 ns here
* intd : LSI internal delay = 50 ns here
* ticf : I2C SCL falling time
* tr : I2C SCL rising time
* intd : LSI internal delay
* clkp : peripheral_clk
* F[] : integer up-valuation
*/
@ -211,12 +214,12 @@ static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv, struct i2c_timin
* it is impossible to calculate large scale
* number on u32. separate it
*
* F[(ticf + tr + intd) * ick]
* = F[(35 + 200 + 50)ns * ick]
* = F[285 * ick / 1000000000]
* = F[(ick / 1000000) * 285 / 1000]
* F[(ticf + tr + intd) * ick] with sum = (ticf + tr + intd)
* = F[sum * ick / 1000000000]
* = F[(ick / 1000000) * sum / 1000]
*/
round = (ick + 500000) / 1000000 * 285;
sum = t->scl_fall_ns + t->scl_rise_ns + t->scl_int_delay_ns;
round = (ick + 500000) / 1000000 * sum;
round = (round + 500) / 1000;
/*