Hello Timur,
Timur Tabi wrote:
> Currently we define I2C_TIMEOUT like this:
>
> #define I2C_TIMEOUT (CONFIG_SYS_HZ / 4)
>
> I'm seeing some I2C instability on a new board I'm working on, especially
> with SPD. If I change the above to
>
> #define I2C_TIMEOUT (CONFIG_SYS_HZ / 2)
>
> The problems go away (or at least, so far appear to). Can someone tell me
> why we choose (CONFIG_SYS_HZ / 4) to begin with? The way we use I2C_TIMEOUT
> is confusing:
>
> while (readb(&i2c_dev[i2c_bus_num]->sr) & I2C_SR_MBB) {
> if ((get_ticks() - timeval) > usec2ticks(I2C_TIMEOUT))
> return -1;
> }
>
> CONFIG_HZ is 1000, so I2C_TIMEOUT is equal to 250. However, the way it's
> used, 250 isn't the number of ticks per second, it's used as number of
> microseconds. If CONFIG_HZ is changed to 100, does that mean that we want to
> call usec2ticks(25)?
This seems like a Bug to me.
> I think what we should be doing is this:
>
> #define I2C_TIMEOUT 1000
>
> Surely, one millisecond is not too long of a timeout?
I think this should be Ok. Can you provide a patch?
Thanks for catching this.
bye
Heiko
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