[U-Boot] [u-boot v2] and i2c

[Heiko Schocher]

Hello Sascha,

Sascha Hauer wrote:
> On Tue, Apr 28, 2009 at 09:36:46AM +0200, Heiko Schocher wrote:
>> Hello Sascha,
>>
>> I actually looked in the u-boot-v2.git in the i2c branch,
>> because I wanted to look how things in v2 work, specially
>> I2C Subsystem ... and I have a first question:
> 
> Note that the I2C branch is out of date and probably needs some
> updating. That does not affect your current problem though.

Yep, I know.

>> - In ppc area, we start running from flash and have to relocate
>>   code. Before setting up RAM, we maybe have to read SPD EEprom
>>   over I2C for this. How could this work in v2? I see in
>>   drivers/i2c/i2c-core.c in i2c_register_adapter () an
>>   INIT_LIST_HEAD(&adap->clients);
>>
>>   This could not work, when running from Flash, because we have no
>>   usable RAM ...
>>   So I looked how this device approach globally works, and found in
>>   lib/driver.c in register_device() also:
>>
>>   107
>>   108         list_add_tail(&new_device->list, &device_list);
>>   109         INIT_LIST_HEAD(&new_device->children);
>>   110
>>
>>   so would this device_driver approach in v2 actually only work,
>>   if running from RAM?
> 
> Yes

Hmm... :-(

>> What if we need the devices earlier?
> 
> You would need portions of the driver which bypass the I2C framework.
> I did something similar for the console (see
> drivers/serial/serial_mpc5xxx.c). This is not particularly nice but I

:-(

Ok, thanks for the info.

bye
Heiko
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