* Aaro Koskinen <[email protected]> [090527 07:55]: > Fix scll/sclh calculations for HS and fast modes. Currently the driver > uses equal (roughly) low/high times which will result in too short > low time. > > OMAP3430 TRM gives the following equations: > > F/S: tLow = (scll + 7) * internal_clk > tHigh = (sclh + 5) * internal_clk > HS: tLow = (scll + 7) * fclk > tHigh = (sclh + 5) * fclk > > Furthermore, the I2C specification sets the following minimum values > for HS tLow/tHigh for capacitive bus loads 100 pF (maximum speed 3400) > and 400 pF (maximum speed 1700): > > speed tLow tHigh > 3400 160 ns 60 ns > 1700 320 ns 120 ns > > and for F/S: > > speed tLow tHigh > 400 1300 ns 600 ns > 100 4700 ns 4000 ns > > By using duty cycles 33/66 (HS, F) and 50/50 (S) we stay above these > minimum values. > > Signed-off-by: Aaro Koskinen <[email protected]>
Ben can you please queue this? Acked-by: Tony Lindgren <[email protected]> > --- > drivers/i2c/busses/i2c-omap.c | 25 ++++++++++++++++++------- > 1 files changed, 18 insertions(+), 7 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > index 9919c08..5d9880c 100644 > --- a/drivers/i2c/busses/i2c-omap.c > +++ b/drivers/i2c/busses/i2c-omap.c > @@ -343,17 +343,28 @@ static int omap_i2c_init(struct omap_i2c_dev *dev) > > /* If configured for High Speed */ > if (dev->speed > 400) { > + unsigned long scl; > + > /* For first phase of HS mode */ > - fsscll = internal_clk / (400 * 2) - 6; > - fssclh = internal_clk / (400 * 2) - 6; > + scl = internal_clk / 400; > + fsscll = scl - (scl / 3) - 7; > + fssclh = (scl / 3) - 5; > > /* For second phase of HS mode */ > - hsscll = fclk_rate / (dev->speed * 2) - 6; > - hssclh = fclk_rate / (dev->speed * 2) - 6; > + scl = fclk_rate / dev->speed; > + hsscll = scl - (scl / 3) - 7; > + hssclh = (scl / 3) - 5; > + } else if (dev->speed > 100) { > + unsigned long scl; > + > + /* Fast mode */ > + scl = internal_clk / dev->speed; > + fsscll = scl - (scl / 3) - 7; > + fssclh = (scl / 3) - 5; > } else { > - /* To handle F/S modes */ > - fsscll = internal_clk / (dev->speed * 2) - 6; > - fssclh = internal_clk / (dev->speed * 2) - 6; > + /* Standard mode */ > + fsscll = internal_clk / (dev->speed * 2) - 7; > + fssclh = internal_clk / (dev->speed * 2) - 5; > } > scll = (hsscll << OMAP_I2C_SCLL_HSSCLL) | fsscll; > sclh = (hssclh << OMAP_I2C_SCLH_HSSCLH) | fssclh; > -- > 1.5.4.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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
