ASoC: SOF: core: unregister clients and machine drivers in .shutdown

On a platform shutdown, the expectation for most drivers is that
userspace tasks will release all resources. When those sequences do
not complete, it can be the case that PCM devices exposed by ALSA
cards are used *after* the DSP shutdown completes, leading to a
platform hang.

When the clients and machine drivers provide an _unregister callback,
let's invoke it in the shutdown sequence.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20220216133241.3990281-1-kai.vehmanen@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/core.c

@@ -463,10 +463,19 @@ EXPORT_SYMBOL(snd_sof_device_remove);
 int snd_sof_device_shutdown(struct device *dev)
 {
 	struct snd_sof_dev *sdev = dev_get_drvdata(dev);
+	struct snd_sof_pdata *pdata = sdev->pdata;
 
 	if (IS_ENABLED(CONFIG_SND_SOC_SOF_PROBE_WORK_QUEUE))
 		cancel_work_sync(&sdev->probe_work);
 
+	/*
+	 * make sure clients and machine driver(s) are unregistered to force
+	 * all userspace devices to be closed prior to the DSP shutdown sequence
+	 */
+	sof_unregister_clients(sdev);
+
+	snd_sof_machine_unregister(sdev, pdata);
+
 	if (sdev->fw_state == SOF_FW_BOOT_COMPLETE)
 		return snd_sof_shutdown(sdev);