ASoC: SOF: only allocate debugfs cache buffers for IPC flood entries

snd_sof_debugfs_buf_item() is an exported function and is called from
different locations to initialise different debugfs entries. However
.cache_buf is only needed for IPC flood entries. Limit allocations
respectively.
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Xiuli Pan <xiulipan@outlook.com>
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210315163932.18663-3-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/debug.c

@@ -609,14 +609,16 @@ int snd_sof_debugfs_buf_item(struct snd_sof_dev *sdev,
 	dfse->sdev = sdev;
 
 #if IS_ENABLED(CONFIG_SND_SOC_SOF_DEBUG_IPC_FLOOD_TEST)
-	/*
-	 * cache_buf is unused for SOF_DFSENTRY_TYPE_BUF debugfs entries.
-	 * So, use it to save the results of the last IPC flood test.
-	 */
-	dfse->cache_buf = devm_kzalloc(sdev->dev, IPC_FLOOD_TEST_RESULT_LEN,
-				       GFP_KERNEL);
-	if (!dfse->cache_buf)
-		return -ENOMEM;
+	if (!strncmp(name, "ipc_flood", strlen("ipc_flood"))) {
+		/*
+		 * cache_buf is unused for SOF_DFSENTRY_TYPE_BUF debugfs entries.
+		 * So, use it to save the results of the last IPC flood test.
+		 */
+		dfse->cache_buf = devm_kzalloc(sdev->dev, IPC_FLOOD_TEST_RESULT_LEN,
+					       GFP_KERNEL);
+		if (!dfse->cache_buf)
+			return -ENOMEM;
+	}
 #endif
 
 	debugfs_create_file(name, mode, sdev->debugfs_root, dfse,