iwlwifi: make U-APSD default configurable at compile time

With a significant number of deployed APs, enabling uAPSD leads to the
AP never using aggregation sessions (likely due to the complexities
involved in handling uAPSD in those.) This obviously results in a large
drop in throughput with such APs.

On the other hand, uAPSD can result in some power consumption benefits,
but for now just disable it to get performance with affected APs back
up.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/Kconfig

@@ -87,6 +87,16 @@ config IWLWIFI_BCAST_FILTERING
 	  If unsure, don't enable this option, as some programs might
 	  expect incoming broadcasts for their normal operations.
 
+config IWLWIFI_UAPSD
+	bool "enable U-APSD by default"
+	depends on IWLMVM
+	help
+	  Say Y here to enable U-APSD by default. This may cause
+	  interoperability problems with some APs, manifesting in lower than
+	  expected throughput due to those APs not enabling aggregation
+
+	  If unsure, say N.
+
 menu "Debugging Options"
 
 config IWLWIFI_DEBUG

drivers/net/wireless/iwlwifi/iwl-drv.c

@@ -1254,7 +1254,9 @@ struct iwl_mod_params iwlwifi_mod_params = {
 	.bt_coex_active = true,
 	.power_level = IWL_POWER_INDEX_1,
 	.wd_disable = true,
-	.uapsd_disable = false,
+#ifndef CONFIG_IWLWIFI_UAPSD
+	.uapsd_disable = true,
+#endif /* CONFIG_IWLWIFI_UAPSD */
 	/* the rest are 0 by default */
 };
 IWL_EXPORT_SYMBOL(iwlwifi_mod_params);
@@ -1370,7 +1372,11 @@ MODULE_PARM_DESC(nvm_file, "NVM file name");
 
 module_param_named(uapsd_disable, iwlwifi_mod_params.uapsd_disable,
 		   bool, S_IRUGO);
+#ifdef CONFIG_IWLWIFI_UAPSD
 MODULE_PARM_DESC(uapsd_disable, "disable U-APSD functionality (default: N)");
+#else
+MODULE_PARM_DESC(uapsd_disable, "disable U-APSD functionality (default: Y)");
+#endif
 
 /*
  * set bt_coex_active to true, uCode will do kill/defer