Re: i2c-mpc clocking scheme

[Luotao Fu <l.fu@pengutronix.de>]

Timur Tabi wrote:
> On Thu, Nov 27, 2008 at 9:00 AM, Andre Schwarz
> <andre.schwarz@matrix-vision.de> wrote:
>> All,
>>
>> is anybody working on some improvements regarding configurable I2C
>> frequency inside the i2c-mpc driver ?
>>
>> If not - would anybody be intersted in getting this done, i.e.
>> configurable via device tree ?
> 
> Maybe I'm missing something, but U-Boot configures the I2C bus speed.

i2c-mpc sets the bus clock in kernel with mpc_i2c_setclock. The bus
speed in kernel is indepedent from u-boot.

> It does this because the algorithm is specific to the SOC itself.  For
> example, the 8544 is different from the 8548.  It would be a mess to
> duplicate this code in the kernel.
> 

I did try to write some mechanismen to make the i2c bus speed
configurable for  mpc5200. I found it quite hard to find some algorithm
to calculate the right values in the Timing table of the I2C bus
controller. Anyhow I gave it up after starring at the datasheet for some
time. ;-) I can't speak for other platforms, which are supported by
i2c-mpc. Anyway, I do think it might be interesting to have configurable
i2c bus speed.

cheers
Luotao Fu
-- 
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Pengutronix - Linux Solutions for Science and Industry
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