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ASoC: wm8904: Add DMIC and DRC support
Merge series from Francesco Dolcini <francesco@dolcini.it>: This patch series adds DMIC and DRC support to the WM8904 driver, a new of_ helper is added to simplify the driver code. DRC functionality is added in the same patch series to provide the necessary dynamic range control to make DMIC support useful. The WM8904 supports digital microphones on two of its inputs: IN1L/DMICDAT1 and IN1R/DMICDAT2. These two inputs can either be connected to an ADC or to the DMIC system. There is an ADC for each line, and only one DMIC block. This DMIC block is either connected to DMICDAT1 or to DMICDAT2. One DMIC data line supports two digital microphones via time multiplexing. The pin's functionality is decided during hardware design (IN1L vs DMICDAT1 and IN1R vs DMICDAT2). This is reflected in the Device Tree. If one line is analog and one is DMIC, we need to be able to switch between ADC and DMIC at runtime. The DMIC source is known from the Device Tree. If both are DMIC inputs, we need to be able to switch the DMIC source. There is no need to switch between ADC and DMIC at runtime. Therefore, kcontrols are dynamically added by the driver depending on its Device Tree configuration. This is a heavy rework of a previous patch series provided by Alifer Moraes and Pierluigi Passaro, https://lore.kernel.org/lkml/20220307141041.27538-1-alifer.m@variscite.com.