[PATCH 1/2 V3] MXS: Set I2C timing registers for mxs-i2c

[marex@denx.de (Marek Vasut)]

Dear Shawn Guo,

> On Mon, Jun 11, 2012 at 12:53:17PM +0200, Marek Vasut wrote:
> > Ok, then can you please try asking them how to exactly compute the values
> > in timing0-timing2 registers? So we don't have to hardcode them like
> > it's done now?
> 
> It's determined I2C clock waveform you want to get.  See i.MX28 RM
> "Figure 27-2. I2C Data and Clock Timing" and "Figure 27-3. I2C Data
> and Clock Timing Generation".
> 
> For example, if you run 12MHz APBX clock, and set HIGH_COUNT to 60,
> the I2C clock will have 60 cycle x (1/12MHz) = 5us time for its high
> period.

Ok, I think I see the equation. But what still doesn't make sense is how you got 
to the value of 48 (RCV_COUNT at 95kHz). And how you got 120 for HIGH_COUNT and 
128 for LOW_COUNT?

Were these values based on some measurements, making them the best possible 
values? Won't computation of slightly different values affect reliability of 
this driver?

Best regards,
Marek Vasut