[U-Boot] MPC8572E I2C bus speed after emulator reset

[Timur Tabi]

On Fri, Mar 27, 2009 at 11:52 AM, Scott Coulter
<scott.coulter at cyclone.com> wrote:

> I have an older version of U-boot for the board which is based of the
> initial port that Kumar did (no MP support, etc.).  With this version of
> U-boot in flash, the "inn" "go" sequence works fine.  The only thing
> that I can think of is that the older U-boot has a different init
> sequence.

You're right, it does.  I wrote the new code. :-)

Previously, U-Boot programmed the same values into the FDR and DFSR
registers, regardless of the input clock rate or whatever divider the
SOC used.  CONFIG_SYS_I2C_SPEED was ignored.

The new code uses a lookup table to determine the best values for FDR
and DFSR for a given input clock rate.  It tries to take into account
the actual divider that your specific SOC uses.  This is done in
function get_clocks().  It's possible that the divider is
miscalculated.

> Does anyone know of way to ensure that the I2C input clock is stable
> before attempting I2C operations?

What is the value of CONFIG_SYS_I2C_SPEED in your board header file?

What values does function set_i2c_bus_speed() in fsl_i2c.c program
into the FDR and DFSR registers?

-- 
Timur Tabi
Linux kernel developer at Freescale