diff options
Diffstat (limited to 'drivers/i2c/omap24xx_i2c.c')
| -rw-r--r-- | drivers/i2c/omap24xx_i2c.c | 66 |
1 files changed, 41 insertions, 25 deletions
diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c index 0006343104..26996e9db9 100644 --- a/drivers/i2c/omap24xx_i2c.c +++ b/drivers/i2c/omap24xx_i2c.c @@ -64,36 +64,52 @@ struct omap_i2c { static int omap24_i2c_findpsc(u32 *pscl, u32 *psch, uint speed) { - unsigned int sampleclk, prescaler; - int fsscll, fssclh; + unsigned long internal_clk = 0, fclk; + unsigned int prescaler; - speed <<= 1; - prescaler = 0; /* - * some divisors may cause a precission loss, but shouldn't - * be a big thing, because i2c_clk is then allready very slow. + * This method is only called for Standard and Fast Mode speeds + * + * For some TI SoCs it is explicitly written in TRM (e,g, SPRUHZ6G, + * page 5685, Table 24-7) + * that the internal I2C clock (after prescaler) should be between + * 7-12 MHz (at least for Fast Mode (FS)). + * + * Such approach is used in v4.9 Linux kernel in: + * ./drivers/i2c/busses/i2c-omap.c (omap_i2c_init function). */ - while (prescaler <= 0xFF) { - sampleclk = I2C_IP_CLK / (prescaler+1); - fsscll = sampleclk / speed; - fssclh = fsscll; - fsscll -= I2C_FASTSPEED_SCLL_TRIM; - fssclh -= I2C_FASTSPEED_SCLH_TRIM; - - if (((fsscll > 0) && (fssclh > 0)) && - ((fsscll <= (255-I2C_FASTSPEED_SCLL_TRIM)) && - (fssclh <= (255-I2C_FASTSPEED_SCLH_TRIM)))) { - if (pscl) - *pscl = fsscll; - if (psch) - *psch = fssclh; - - return prescaler; - } - prescaler++; + speed /= 1000; /* convert speed to kHz */ + + if (speed > 100) + internal_clk = 9600; + else + internal_clk = 4000; + + fclk = I2C_IP_CLK / 1000; + prescaler = fclk / internal_clk; + prescaler = prescaler - 1; + + if (speed > 100) { + unsigned long scl; + + /* Fast mode */ + scl = internal_clk / speed; + *pscl = scl - (scl / 3) - I2C_FASTSPEED_SCLL_TRIM; + *psch = (scl / 3) - I2C_FASTSPEED_SCLH_TRIM; + } else { + /* Standard mode */ + *pscl = internal_clk / (speed * 2) - I2C_FASTSPEED_SCLL_TRIM; + *psch = internal_clk / (speed * 2) - I2C_FASTSPEED_SCLH_TRIM; } - return -1; + + debug("%s: speed [kHz]: %d psc: 0x%x sscl: 0x%x ssch: 0x%x\n", + __func__, speed, prescaler, *pscl, *psch); + + if (*pscl <= 0 || *psch <= 0 || prescaler <= 0) + return -EINVAL; + + return prescaler; } /* |