* Aaro Koskinen <aaro.koskinen@xxxxxxxxx> [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 <aaro.koskinen@xxxxxxxxx>
Ben can you please queue this?
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
> ---
> 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
>
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