ALSA: hda: intel-dsp-config: Add SND_INTEL_BYT_PREFER_SOF Kconfig option

The kernel has 2 drivers for the Low Power Engine audio-block on
Bay- and Cherry-Trail SoCs. The old SST driver and the new SOF
driver. If both drivers are enabled then the kernel will default
to using the old SST driver, unless told otherwise through the
snd_intel_dspcfg.dsp_driver module-parameter.

Add a boolean SND_INTEL_BYT_PREFER_SOF Kconfig option, which when set to Y
will make the kernel default to the new SOF driver instead.
The option defaults to n, preserving the current behavior.

Making this configurable will help distributions such as Fedora:
https://fedoraproject.org/w/index.php?title=Changes/SofDefaultForIntelLpe
to test using SOF on BYT/CHT during the transition phase where we
have both drivers (eventually the old driver and this option will
be removed).

Note that this drops the acpi_config_table[] containing 2 entries per ACPI
hardware-id if both drivers are enabled. snd_intel_acpi_dsp_find_config()
will always return the first hit, so we only need a single entry with the
flags value set depending on the Kconfig settings.

Suggested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210208135919.135600-1-hdegoede@redhat.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/hda/Kconfig

@@ -46,3 +46,17 @@ config SND_INTEL_DSP_CONFIG
 	select SND_INTEL_NHLT if ACPI
 	# this config should be selected only for Intel DSP platforms.
 	# A fallback is provided so that the code compiles in all cases.
+
+config SND_INTEL_BYT_PREFER_SOF
+	bool "Prefer SOF driver over SST on BY/CHT platforms"
+	depends on SND_SST_ATOM_HIFI2_PLATFORM_ACPI && SND_SOC_SOF_BAYTRAIL
+	default n
+	help
+	  The kernel has 2 drivers for the Low Power Engine audio-block on
+	  Bay- and Cherry-Trail SoCs. The old SST driver and the new SOF
+	  driver. If both drivers are enabled then the kernel will default
+	  to using the old SST driver, unless told otherwise through the
+	  snd_intel_dspcfg.dsp_driver module-parameter.
+
+	  Set this option to Y to make the kernel default to the new SOF
+	  driver instead.

sound/hda/intel-dsp-config.c

@@ -452,35 +452,30 @@ int snd_intel_dsp_driver_probe(struct pci_dev *pci)
 }
 EXPORT_SYMBOL_GPL(snd_intel_dsp_driver_probe);
 
+/* Should we default to SOF or SST for BYT/CHT ? */
+#if IS_ENABLED(CONFIG_SND_INTEL_BYT_PREFER_SOF) || \
+    !IS_ENABLED(CONFIG_SND_SST_ATOM_HIFI2_PLATFORM_ACPI)
+#define FLAG_SST_OR_SOF_BYT	FLAG_SOF
+#else
+#define FLAG_SST_OR_SOF_BYT	FLAG_SST
+#endif
+
 /*
  * configuration table
  * - the order of similar ACPI ID entries is important!
  * - the first successful match will win
  */
 static const struct config_entry acpi_config_table[] = {
+#if IS_ENABLED(CONFIG_SND_SST_ATOM_HIFI2_PLATFORM_ACPI) || \
+    IS_ENABLED(CONFIG_SND_SOC_SOF_BAYTRAIL)
 /* BayTrail */
-#if IS_ENABLED(CONFIG_SND_SST_ATOM_HIFI2_PLATFORM_ACPI)
 	{
-		.flags = FLAG_SST,
+		.flags = FLAG_SST_OR_SOF_BYT,
 		.acpi_hid = "80860F28",
 	},
-#endif
-#if IS_ENABLED(CONFIG_SND_SOC_SOF_BAYTRAIL)
-	{
-		.flags = FLAG_SOF,
-		.acpi_hid = "80860F28",
-	},
-#endif
 /* CherryTrail */
-#if IS_ENABLED(CONFIG_SND_SST_ATOM_HIFI2_PLATFORM_ACPI)
 	{
-		.flags = FLAG_SST,
-		.acpi_hid = "808622A8",
-	},
-#endif
-#if IS_ENABLED(CONFIG_SND_SOC_SOF_BAYTRAIL)
-	{
-		.flags = FLAG_SOF,
+		.flags = FLAG_SST_OR_SOF_BYT,
 		.acpi_hid = "808622A8",
 	},
 #endif