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, 5 insertions, 0 deletions

diff --git a/sound/soc/sof/sof-audio.c b/sound/soc/sof/sof-audio.c
index 62092e2d609c..7306a2649857 100644
--- a/sound/soc/sof/sof-audio.c
+++ b/sound/soc/sof/sof-audio.c
@@ -826,6 +826,10 @@ int sof_machine_check(struct snd_sof_dev *sdev)
 	if (!IS_ENABLED(CONFIG_SND_SOC_SOF_FORCE_NOCODEC_MODE)) {
 		const struct snd_sof_of_mach *of_mach;
 
+		if (IS_ENABLED(CONFIG_SND_SOC_SOF_NOCODEC_DEBUG_SUPPORT) &&
+		    sof_debug_check_flag(SOF_DBG_FORCE_NOCODEC))
+			goto nocodec;
+
 		/* find machine */
 		mach = snd_sof_machine_select(sdev);
 		if (mach) {
@@ -848,6 +852,7 @@ int sof_machine_check(struct snd_sof_dev *sdev)
 		dev_warn(sdev->dev, "Force to use nocodec mode\n");
 	}
 
+nocodec:
 	/* select nocodec mode */
 	dev_warn(sdev->dev, "Using nocodec machine driver\n");
 	mach = devm_kzalloc(sdev->dev, sizeof(*mach), GFP_KERNEL);