Re: [PATCH v2 1/2] i2c-designware: make HCNT/LCNT values configurable

From: Wolfram Sang
Date: Wed Aug 28 2013 - 05:10:28 EST


On Mon, Aug 19, 2013 at 03:07:53PM +0300, Mika Westerberg wrote:
> The DesignWare I2C controller has high count (HCNT) and low count (LCNT)
> registers for each of the I2C speed modes (standard and fast). These
> registers are programmed based on the input clock speed in the driver.
>
> The current code calculates these values based on the input clock speed and
> tries hard to meet the I2C bus timing requirements. This could result
> non-optimal values with regarding to the bus speed. For example on Intel
> BayTrail we get bus speed of 315.41kHz which is ~20% slower than we would
> expect (400kHz) in fast mode (even though the timing requirements are met).
>
> This patch makes it possible for the platform code to pass more optimal
> HCNT/LCNT values to the core driver if they are known beforehand. If these
> are not set we use the calculated and more conservative values.
>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>

Applied to for-next, thanks!

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