[U-Boot] A question about unconfigured pads check in omap24xx_i2c

[Heiko Schocher <hs@denx.de>]

Hello Lubomir,

Am 06.11.2013 14:19, schrieb Lubomir Popov:
> On 06-Nov-13 14:12, Nikita Kiryanov wrote:
>> In drivers/i2c/omap24xx_i2c.c there are a few checks that attempt to
>> detect unconfigured pads for the i2c bus in use. These checks are
>> all in the form of
>>
>> if (status == I2C_STAT_XRDY) {
>> printf("unconfigured pads\n");
>> return -1;
>> }
>>
>> This check seems peculiar to me since the meaning of I2C_STAT_XRDY is
>> that new data is requested for transmission. Why is that indication that
>> the bus is not padconf'd for I2C?
> Hi Nikita,
>
> This has been empirically confirmed on OMAP4 and OMAP5. When the pads are not
> configured, the I2C controller is actually disconnected from the bus. The clock
> input for its state machine has to come from the bus however due to stretching
> etc., although it is internally generated. So actually nothing changes within
> the controller after a transaction attempt is made, and it keeps its initial
> state with XRDY set only (ready to accept transmit data). I use this as an
> indicator. Not perfect, but works in most cases.

Thanks for this explanation! Maybe we can document this somewhere in
the code?

bye,
Heiko
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