ALSA: hda - introduce snd_hda_codec_update_cache()

Add a new helper, snd_hda_codec_update_cache(), for reducing the unneeded
verbs.  This function checks the cached value and skips if it's identical
with the given one.  Otherwise it works like snd_hda_codec_write_cache().

The alc269 code uses this function as an example.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 56 insertions, 12 deletions

diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index d1424e7b9f3d..a3d638c8c1fd 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -1209,8 +1209,7 @@ static void free_hda_cache(struct hda_cache_rec *cache)
 }
 
 /* query the hash.  allocate an entry if not found. */
-static struct hda_cache_head  *get_alloc_hash(struct hda_cache_rec *cache,
-					      u32 key)
+static struct hda_cache_head  *get_hash(struct hda_cache_rec *cache, u32 key)
 {
 	u16 idx = key % (u16)ARRAY_SIZE(cache->hash);
 	u16 cur = cache->hash[idx];
@@ -1222,17 +1221,27 @@ static struct hda_cache_head  *get_alloc_hash(struct hda_cache_rec *cache,
 			return info;
 		cur = info->next;
 	}
+	return NULL;
+}
 
-	/* add a new hash entry */
-	info = snd_array_new(&cache->buf);
-	if (!info)
-		return NULL;
-	cur = snd_array_index(&cache->buf, info);
-	info->key = key;
-	info->val = 0;
-	info->next = cache->hash[idx];
-	cache->hash[idx] = cur;
-
+/* query the hash.  allocate an entry if not found. */
+static struct hda_cache_head  *get_alloc_hash(struct hda_cache_rec *cache,
+					      u32 key)
+{
+	struct hda_cache_head *info = get_hash(cache, key);
+	if (!info) {
+		u16 idx, cur;
+		/* add a new hash entry */
+		info = snd_array_new(&cache->buf);
+		if (!info)
+			return NULL;
+		cur = snd_array_index(&cache->buf, info);
+		info->key = key;
+		info->val = 0;
+		idx = key % (u16)ARRAY_SIZE(cache->hash);
+		info->next = cache->hash[idx];
+		cache->hash[idx] = cur;
+	}
 	return info;
 }
 
@@ -2722,6 +2731,41 @@ int snd_hda_codec_write_cache(struct hda_codec *codec, hda_nid_t nid,
 EXPORT_SYMBOL_HDA(snd_hda_codec_write_cache);
 
 /**
+ * snd_hda_codec_update_cache - check cache and write the cmd only when needed
+ * @codec: the HDA codec
+ * @nid: NID to send the command
+ * @direct: direct flag
+ * @verb: the verb to send
+ * @parm: the parameter for the verb
+ *
+ * This function works like snd_hda_codec_write_cache(), but it doesn't send
+ * command if the parameter is already identical with the cached value.
+ * If not, it sends the command and refreshes the cache.
+ *
+ * Returns 0 if successful, or a negative error code.
+ */
+int snd_hda_codec_update_cache(struct hda_codec *codec, hda_nid_t nid,
+			       int direct, unsigned int verb, unsigned int parm)
+{
+	struct hda_cache_head *c;
+	u32 key;
+
+	/* parm may contain the verb stuff for get/set amp */
+	verb = verb | (parm >> 8);
+	parm &= 0xff;
+	key = build_cmd_cache_key(nid, verb);
+	mutex_lock(&codec->bus->cmd_mutex);
+	c = get_hash(&codec->cmd_cache, key);
+	if (c && c->val == parm) {
+		mutex_unlock(&codec->bus->cmd_mutex);
+		return 0;
+	}
+	mutex_unlock(&codec->bus->cmd_mutex);
+	return snd_hda_codec_write_cache(codec, nid, direct, verb, parm);
+}
+EXPORT_SYMBOL_HDA(snd_hda_codec_update_cache);
+
+/**
  * snd_hda_codec_resume_cache - Resume the all commands from the cache
  * @codec: HD-audio codec
  *