[alsa-devel] [RFC PATCH v2 1/3] ALSA: hda - add DP mst verb support

[libin.yang at linux.intel.com]

From: Libin Yang <libin.yang at linux.intel.com>

Add snd_hda_get_dev_select() and snd_hda_set_dev_select() functions
for DP MST audio support.

Signed-off-by: Libin Yang <libin.yang at linux.intel.com>
---
 sound/pci/hda/hda_codec.c | 83 ++++++++++++++++++++++++++++++++++++++++++++---
 sound/pci/hda/hda_codec.h |  3 ++
 2 files changed, 82 insertions(+), 4 deletions(-)

diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index d17e38e..db94a66 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -325,9 +325,16 @@ int snd_hda_get_conn_index(struct hda_codec *codec, hda_nid_t mux,
 }
 EXPORT_SYMBOL_GPL(snd_hda_get_conn_index);
 
-
-/* return DEVLIST_LEN parameter of the given widget */
-static unsigned int get_num_devices(struct hda_codec *codec, hda_nid_t nid)
+/**
+ * snd_hda_get_num_devices - get DEVLIST_LEN parameter of the given widget
+ *  @codec: the HDA codec
+ *  @nid: NID of the pin to parse
+ *
+ * Get the device entry number on the given widget.
+ * This is a feature of DP MST audio. Each pin can
+ * have several device entries in it.
+ */
+unsigned int snd_hda_get_num_devices(struct hda_codec *codec, hda_nid_t nid)
 {
 	unsigned int wcaps = get_wcaps(codec, nid);
 	unsigned int parm;
@@ -341,6 +348,7 @@ static unsigned int get_num_devices(struct hda_codec *codec, hda_nid_t nid)
 		parm = 0;
 	return parm & AC_DEV_LIST_LEN_MASK;
 }
+EXPORT_SYMBOL_GPL(snd_hda_get_num_devices);
 
 /**
  * snd_hda_get_devices - copy device list without cache
@@ -358,7 +366,7 @@ int snd_hda_get_devices(struct hda_codec *codec, hda_nid_t nid,
 	unsigned int parm;
 	int i, dev_len, devices;
 
-	parm = get_num_devices(codec, nid);
+	parm = snd_hda_get_num_devices(codec, nid);
 	if (!parm)	/* not multi-stream capable */
 		return 0;
 
@@ -382,6 +390,73 @@ int snd_hda_get_devices(struct hda_codec *codec, hda_nid_t nid,
 	return devices;
 }
 
+/**
+ * snd_hda_get_dev_select - get device entry select on the pin
+ * @codec: the HDA codec
+ * @nid: NID of the pin to get device entry select
+ *
+ * Get the devcie entry select on the pin. Return the device entry
+ * id selected on the pin. Return 0 means the first device entry
+ * is selected or MST is not supported.
+ */
+int snd_hda_get_dev_select(struct hda_codec *codec, hda_nid_t nid)
+{
+	/* not support dp_mst will always return 0, using first dev_entry */
+	if (!codec->dp_mst)
+		return 0;
+
+	return snd_hda_codec_read(codec, nid, 0, AC_VERB_GET_DEVICE_SEL, 0);
+}
+EXPORT_SYMBOL_GPL(snd_hda_get_dev_select);
+
+/**
+ * snd_hda_set_dev_select - set device entry select on the pin
+ * @codec: the HDA codec
+ * @nid: NID of the pin to set device entry select
+ * @dev_id: device entry id to be set
+ *
+ * Set the device entry select on the pin nid.
+ */
+int snd_hda_set_dev_select(struct hda_codec *codec, hda_nid_t nid, int dev_id)
+{
+	int ret, dev, num_devices;
+	unsigned long timeout;
+
+	/* not support dp_mst will always return 0, using first dev_entry */
+	if (!codec->dp_mst)
+		return 0;
+
+	/* AC_PAR_DEVLIST_LEN is 0 based. */
+	num_devices = snd_hda_get_num_devices(codec, nid);
+	/* If Device List Length is 0, the pin is not multi stream capable.
+	 */
+	if (num_devices == 0)
+		return 0;
+
+	/* Behavior of setting index being equal to or greater than
+	 * Device List Length is not predictable
+	 */
+	if (num_devices + 1 <= dev_id)
+		return 0;
+
+	timeout = jiffies + msecs_to_jiffies(500);
+
+	/* make sure the device entry selection takes effect */
+	do {
+		ret = snd_hda_codec_write(codec, nid, 0,
+			AC_VERB_SET_DEVICE_SEL, dev_id);
+		udelay(20);
+
+		dev = snd_hda_get_dev_select(codec, nid);
+		if (dev == dev_id)
+			break;
+		msleep(20);
+	} while (time_before(jiffies, timeout));
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(snd_hda_set_dev_select);
+
 /*
  * read widget caps for each widget and store in cache
  */
diff --git a/sound/pci/hda/hda_codec.h b/sound/pci/hda/hda_codec.h
index 4852c1a..57d1659 100644
--- a/sound/pci/hda/hda_codec.h
+++ b/sound/pci/hda/hda_codec.h
@@ -348,8 +348,11 @@ int snd_hda_override_conn_list(struct hda_codec *codec, hda_nid_t nid,
 			       int dev_id, int nums, const hda_nid_t *list);
 int snd_hda_get_conn_index(struct hda_codec *codec, hda_nid_t mux,
 			   hda_nid_t nid, int dev_id, int recursive);
+unsigned int snd_hda_get_num_devices(struct hda_codec *codec, hda_nid_t nid);
 int snd_hda_get_devices(struct hda_codec *codec, hda_nid_t nid,
 			u8 *dev_list, int max_devices);
+int snd_hda_get_dev_select(struct hda_codec *codec, hda_nid_t nid);
+int snd_hda_set_dev_select(struct hda_codec *codec, hda_nid_t nid, int dev_id);
 
 struct hda_verb {
 	hda_nid_t nid;
-- 
1.9.1