// SPDX-License-Identifier: GPL-2.0
//
// Freescale SSI ALSA SoC Digital Audio Interface (DAI) driver
//
// Author: Timur Tabi <timur@freescale.com>
//
// Copyright 2007-2010 Freescale Semiconductor, Inc.
//
// Some notes why imx-pcm-fiq is used instead of DMA on some boards:
//
// The i.MX SSI core has some nasty limitations in AC97 mode. While most
// sane processor vendors have a FIFO per AC97 slot, the i.MX has only
// one FIFO which combines all valid receive slots. We cannot even select
// which slots we want to receive. The WM9712 with which this driver
// was developed with always sends GPIO status data in slot 12 which
// we receive in our (PCM-) data stream. The only chance we have is to
// manually skip this data in the FIQ handler. With sampling rates different
// from 48000Hz not every frame has valid receive data, so the ratio
// between pcm data and GPIO status data changes. Our FIQ handler is not
// able to handle this, hence this driver only works with 48000Hz sampling
// rate.
// Reading and writing AC97 registers is another c
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