ASoC: SOF: introduce new DEBUG_NOCODEC mode

The existing NOCODEC mode enforces a build-time mutual exclusion with
the HDaudio link support, mostly to avoid any dependency on the
snd_hdac library and references to HDAudio codec/i915 stuff.

This is very useful to track dependencies and test a minimal
configuration, but very painful for developers and CI: a recompilation
and reinstall of the kernel modules is required.

This patch suggests an alternate middle ground where the selection of
the machine driver and all codec-related actions are bypassed at
run-time, contingent on a kernel module parameter being set.

For example setting BIT(10) with
'options snd_sof sof_debug=0x401'
is enough to switch from an HDaudio card to a nocodec one.

This new DEBUG_NOCODEC mode is not suitable for distributions and
end-users. It's not even recommended on all platforms, i.e. the
NOCODEC mode is known not to work on specific devices where the BIOS
did not configure support for I2S/DMIC interfaces. The usual
development devices such as Chromebooks, Up boards and Intel RVP are
the only recommended platforms where this mode can be supported.

Note that the dynamic switch between HDaudio and nocodec may not
always possible depending on hardware layout, pin-mux options, and
BIOS settings. The audio subsustems on Intel platforms has to support
4 types of interfaces and pin-mux can be complicated.

Reviewers might ask: why didn't we do this earlier? The main reason is
that all the codec-related configurations were not cleanly separated
out in the sof/intel directory. With all the cleanups done recently,
adding this opt-in behavior is relatively straightforward.

Tested on UpExtreme (WHL) and UpExtreme i11 (TGL).

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20221027193540.259520-22-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 16 insertions, 2 deletions

diff --git a/sound/soc/sof/Kconfig b/sound/soc/sof/Kconfig
index 37f7df5fde17..0b9beb74b0f6 100644
--- a/sound/soc/sof/Kconfig
+++ b/sound/soc/sof/Kconfig
@@ -97,13 +97,13 @@ config SND_SOC_SOF_NOCODEC
 	tristate
 
 config SND_SOC_SOF_NOCODEC_SUPPORT
-	bool "SOF nocodec mode support"
+	bool "SOF nocodec static mode support"
 	help
 	  This adds support for a dummy/nocodec machine driver fallback
 	  option if no known codec is detected. This is typically only
 	  enabled for developers or devices where the sound card is
 	  controlled externally.
-	  This option is mutually exclusive with the Intel HDAudio support.
+	  This option is mutually exclusive at build time with the Intel HDAudio support.
 	  Selecting it may have negative impacts and prevent e.g. microphone
 	  functionality from being enabled on Intel CoffeeLake and later
 	  platforms.
@@ -136,6 +136,19 @@ config SND_SOC_SOF_DEBUG
 
 if SND_SOC_SOF_DEBUG
 
+config SND_SOC_SOF_NOCODEC_DEBUG_SUPPORT
+	bool "SOF nocodec debug mode support"
+	depends on !SND_SOC_SOF_NOCODEC_SUPPORT
+	help
+	  This adds support for a dummy/nocodec machine driver fallback
+	  option.
+	  Unlike the SND_SOC_SOF_NOCODEC_SUPPORT, this option is NOT
+	  mutually exclusive at build with the Intel HDAudio support. The
+	  selection will be done depending on command line or modprobe.d settings
+	  Distributions should not select this option!
+	  Say Y if you need this nocodec debug fallback option.
+	  If unsure select "N".
+
 config SND_SOC_SOF_FORCE_NOCODEC_MODE
 	bool "SOF force nocodec Mode"
 	depends on SND_SOC_SOF_NOCODEC_SUPPORT
@@ -239,6 +252,7 @@ config SND_SOC_SOF
 	tristate
 	select SND_SOC_TOPOLOGY
 	select SND_SOC_SOF_NOCODEC if SND_SOC_SOF_NOCODEC_SUPPORT
+	select SND_SOC_SOF_NOCODEC if SND_SOC_SOF_NOCODEC_DEBUG_SUPPORT
 	help
 	  This option is not user-selectable but automagically handled by
 	  'select' statements at a higher level.