[PATCH 2/2] ALSA: hda: intel-dsp-config: Add SND_INTEL_BYT_PREFER_SOF Kconfig option

[Hans de Goede <hdegoede@redhat.com>]

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.

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 the option defaults to n, preserving the current behavior.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 sound/hda/Kconfig            | 14 ++++++++++++++
 sound/hda/intel-dsp-config.c |  5 +++++
 2 files changed, 19 insertions(+)

diff --git a/sound/hda/Kconfig b/sound/hda/Kconfig
index 3bc9224d5e4f..9ed5cfa3c18c 100644
--- a/sound/hda/Kconfig
+++ b/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.
diff --git a/sound/hda/intel-dsp-config.c b/sound/hda/intel-dsp-config.c
index 2201a1e6944e..fd288df7ede9 100644
--- a/sound/hda/intel-dsp-config.c
+++ b/sound/hda/intel-dsp-config.c
@@ -454,8 +454,13 @@ EXPORT_SYMBOL_GPL(snd_intel_dsp_driver_probe);
 
 /* FLAG_BYT_FIRST / _SECOND determine which driver is preferred on BYT/CHT when both are enabled */
 #if IS_ENABLED(CONFIG_SND_SST_ATOM_HIFI2_PLATFORM_ACPI) && IS_ENABLED(CONFIG_SND_SOC_SOF_BAYTRAIL)
+#ifdef CONFIG_SND_INTEL_BYT_PREFER_SOF
+#define FLAG_BYT_FIRST		FLAG_SOF
+#define FLAG_BYT_SECOND		FLAG_SST
+#else
 #define FLAG_BYT_FIRST		FLAG_SST
 #define FLAG_BYT_SECOND		FLAG_SOF
+#endif
 #elif IS_ENABLED(CONFIG_SND_SST_ATOM_HIFI2_PLATFORM_ACPI)
 #define FLAG_BYT_FIRST		FLAG_SST
 #elif IS_ENABLED(CONFIG_SND_SOC_SOF_BAYTRAIL)
-- 
2.30.0