On 10/12/15 17:31, Petr Kulhavy wrote: > Hi, > > I'm developing a DT-based driver for an ARM SoC device with the > following special clock routing: > > - WM8758 codec attached to the CPU DAI via I2S > - the codec is I2S clock master > - the CPU feeds the codec with 12MHz clock (outside of the I2S) > - the codec converts the 12MHz internally to 48kHz*256 or 44.1kHz *256 > clock and provides it to I2S as MCLK > > So the special set-up needed here is that the codec needs to be > configured to: > a) generate the proper MCLK > b) enable the respective GPIO pin as clock output > > What is the best way of representing this set-up using device tree? > I'm wondering if this can be done by adding a specific option in the > codec DT binding for enabling the clock output and then use the simple > audio card. > Or do I need to write a specific soundcard driver that sets up the codec > registers? I would like to avoid that if possible and use existing code... > > What would you recommend? I assume when the clock enable/disable code is not there it could be added to the codec driver, e.g. like in case of max98090. The clock source just needs to be exposed as a common clock object. As an example of similar setup you could take a look at arch/arm/boot/dts/exynos4412-odroid-common.dts. The difference was that in case of Odroid the clock was generated by a PLL inside a SoC, then it was routed to I2S which fed the clock to the codec through the SoC's io pin. The codec was I2S master and the I2S IP block was actually a source of its main ("mclk") clock. I hope this helps. -- Regards, Sylwester _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel