[U-Boot] [PATCH] 85xx: Using proper I2C source clock divider for MPC8544

[Wolfgang Grandegger]

Kumar Gala wrote:
> 
> On Oct 14, 2008, at 2:11 PM, Wolfgang Grandegger wrote:
> 
>> Kumar Gala wrote:
>>> On Oct 10, 2008, at 2:29 AM, Wolfgang Grandegger wrote:
>>>
>>>> Kumar Gala wrote:
>>>>> On Sep 30, 2008, at 3:55 AM, Wolfgang Grandegger wrote:
>>>>>
>>>>>> Measurements with our MPC8544 board showed that the I2C bus
>>>>>> frequency
>>>>>> is wrong by a factor of 1.5. Obviously, the interpretation of the
>>>>>> MPC85xx_PORDEVSR2_SEC_CFG bit of the cfg_sec_freq register is not
>>>>>> correct. There seems to be an error in the 8544 RM.
>>>>>>
>>>>>> Signed-off-by: Wolfgang Grandegger <wg at grandegger.com>
>>>>>> ---
>>>>>> cpu/mpc85xx/speed.c |    4 ++--
>>>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>> can you do me a favor and dump the value of MPC85xx_PORDEVSR2.  Also
>>>>> can you tell me what rev 8544 you have.
>>>> See below:
>>>>
>>>> pordevsr2 at e00e0014=0x8f00007d
>>>>
>>>> CPU:   8544E, Version: 1.1, (0x803c0111)
>>>> Core:  E500, Version: 2.2, (0x80210022)
>>>> Clock Configuration:
>>>>        CPU: 667 MHz, CCB: 334 MHz,
>>>>        DDR: 167 MHz (334 MT/s data rate), LBC:  41 MHz
>>>> L1:    D-cache 32 kB enabled
>>>>        I-cache 32 kB enabled
>>>> Board: Socrates
>>>>
>>>> Wolfgang.
>>>
>>> thanks.  How did you do the measurements that got you this 1.5x factor?
>>
>> This afternoon I re-measured the I2C bus clock frequency with the
>> oscilloscope at the I2C clock line on our Socrates MPC8544 board. With
>> the patch applied, I measured the correct frequency of 100 kHz. Without,
>> it was a factor of 1.5 too high.
> 
> are you able to change cfg_seq_freq on the board?

At least I don't know how. It's defined via hardware strap, I imagine.

Wolfgang.