drivers: audio: dmic_nrfx: Add support for nRF54H20

[mstasiaknordic]

PDM driver can now be used on nRF54H20. It required an addition of DMM mechanism and minor changes to clock management,
nRF54H20 does not require clock control in case of PDM driver.

Currently, product specification for nRF54H20 PDM does not provide fully correct formula to calculate PDM clock frequency, thus master clock source frequency has to be passed as 8 MHz to ensure proper driver behavior. To be corrected and removed once correct formula is found.

[nika-nordic]

I am approving but dmm calls needs to be fixed, could be done later

[nika-nordic]

I think this is wrong and won't work if non-DMAble buffer is provided - API of dma_buffer_in_prepare looks like this:

zephyr/soc/nordic/common/dmm.h

Line 142 in 065bd32

int dmm_buffer_in_prepare(void *region, void *user_buffer, size_t user_length, void **buffer_in);

So you should have additional pointer void *dma_buffer , use it in dma_buffer_in_prepare and then in nrfx_pdm_buffer_set :

struct dmic_nrfx_pdm_drv_data {
	const nrfx_pdm_t *pdm;
	struct onoff_manager *clk_mgr;
        void *memslab_buffer;
};

void event_handler() {
void *dma_buffer;

k_mem_slab_alloc(drv_data->mem_slab, &dev->data->memslab_buffer, K_NO_WAIT);
dmm_buffer_in_prepare(drv_cfg->mem_reg, dev->data->memslab_buffer,
	              drv_data->block_size,
                      &dma_buffer);
nrfx_pdm_buffer_set(drv_data->pdm, dma_buffer, drv_data->block_size / 2);
}

Then, when PDM is stopped or buffer is filled with data, and the DMA buffer is to be freed:

else if (evt->buffer_released) {
	       ret = dmm_buffer_in_release(drv_cfg->mem_reg, dev->data->memslab_buffer,
						  drv_data->block_size,
						  evt->buffer_released);
		ret = k_msgq_put(&drv_data->rx_queue,
				 dev->data->memslab_buffer,
				 K_NO_WAIT);
               /* User calls k_mem_slab_free on original `dev->data->memslab_buffer`  */

Similar code needs to be applied to if (drv_data->stopping) { conditional

It works right now because dmm calls does nothing if memslab is completely preallocated in correct region, and this seem to be the case for existing tests