[PATCH v2] ALSA: hda/hdmi: let new platforms assign the pcm slot dynamically

[Hui Wang <hui.wang@canonical.com>]

If the platform set the dyn_pcm_assign to true, it will call
hdmi_find_pcm_slot() to find a pcm slot when hdmi/dp monitor is
connected and need to create a pcm.

So far only intel_hsw_common_init() and patch_nvhdmi() set the
dyn_pcm_assign to true, here we let tgl platforms assign the pcm slot
dynamically first, if the driver runs for a period of time and there
is no regression reported, we could set no_fixed_assgin to true in
the intel_hsw_common_init(), and then set it to true in the
patch_nvhdmi().

This change comes from the discussion between Takashi and
Kai Vehmanen. Please refer to:
https://github.com/alsa-project/alsa-lib/pull/118

Signed-off-by: Hui Wang <hui.wang@canonical.com>
---
Did the test with this patch on 2 TGL machines, and with both legacy
HDA driver and sof driver, plug 1 monitor into the machine, plug 2
monitors into the machine and plug 2 monitors into a dp-mst hub, they
all worked as expcted, the first 2 pcm slots was assigned to monitors,
and playback worked well.

 sound/pci/hda/patch_hdmi.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index 97adff0cbcab..1aca815b920d 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -157,6 +157,7 @@ struct hdmi_spec {
 
 	bool dyn_pin_out;
 	bool dyn_pcm_assign;
+	bool no_fixed_assign;
 	bool intel_hsw_fixup;	/* apply Intel platform-specific fixups */
 	/*
 	 * Non-generic VIA/NVIDIA specific
@@ -1345,6 +1346,12 @@ static int hdmi_find_pcm_slot(struct hdmi_spec *spec,
 {
 	int i;
 
+	/* on the new machines, try to assign the pcm slot dynamically,
+	 * not use the preferred fixed map anymore.
+	 */
+	if (spec->no_fixed_assign)
+		goto last_try;
+
 	/*
 	 * generic_hdmi_build_pcms() may allocate extra PCMs on some
 	 * platforms (with maximum of 'num_nids + dev_num - 1')
@@ -1374,6 +1381,7 @@ static int hdmi_find_pcm_slot(struct hdmi_spec *spec,
 			return i;
 	}
 
+ last_try:
 	/* the last try; check the empty slots in pins */
 	for (i = 0; i < spec->num_nids; i++) {
 		if (!test_bit(i, &spec->pcm_bitmap))
@@ -2988,8 +2996,16 @@ static int patch_i915_tgl_hdmi(struct hda_codec *codec)
 	 * the index indicate the port number.
 	 */
 	static const int map[] = {0x4, 0x6, 0x8, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf};
+	int ret;
 
-	return intel_hsw_common_init(codec, 0x02, map, ARRAY_SIZE(map));
+	ret = intel_hsw_common_init(codec, 0x02, map, ARRAY_SIZE(map));
+	if (!ret) {
+		struct hdmi_spec *spec = codec->spec;
+
+		spec->no_fixed_assign = true;
+	}
+
+	return ret;
 }
 
 /* Intel Baytrail and Braswell; with eld notifier */
-- 
2.25.1