[alsa-devel] Can't use adau1361 as i2s master due to bad write ordering

[Lars-Peter Clausen]

On 02/03/2016 05:04 PM, Andreas Irestål wrote:
> I've run into problems using the adau1361 codec (adau1761) as i2s master.
> 
> I'm using i2c to set up the codec, and according to the datasheet there
> is an enable bit, which must be set in order to be able to access any
> other register than the first two registers.
> 
> This enable bit is set when the codec enters bias level standby,
> however, before entering this bias level, some other registers are
> written which will have no effect due to the inner workings of this
> codec. Oddly enough, it does ack all writes when measuring the i2c bus.
> 
> One of these registers is the serial port 0 register, which
> configures the i2s bus. This results in the situation that the CODEC dai
> thinks it is running as i2s slave and the CPU dai thinks too as well,
> and the bus is dead. Since the other register fields does not change
> with our dai configuration, the register never gets physically updated
> by an i2c write.
> 
> If I reset/reboot the system, which in our case does not power cycle the
> codec, the i2s bus is correctly set up and everything works as one would
> expect.
> 
> So, either the driver behaves incorrectly relying on bias level being
> set before any other registers are written, or the underlying subsystem
> are behaving incorrectly. We're using the simple-card board driver as it
> is sufficient for our needs.

Hi,

Yes, that sounds like a bug in the driver. We probably need to enable the
clock in the probe() function before we do any other register writes.

- Lars