iwlwifi: avoid debug max amsdu config overwriting itself

If we set amsdu_len one after another the second one overwrites
the orig_amsdu_len so allow only moving from debug to non debug state.

Also the TLC update check was wrong: it was checking that also the orig
is smaller then the new updated size, which is not the case in debug
amsdu mode.
Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Fixes: af2984e9 ("iwlwifi: mvm: add a debugfs entry to set a fixed size AMSDU for all TX packets")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200424182644.e565446a4fce.I9729d8c520d8b8bb4de9a5cdc62e01eb85168aac@changeid

drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c

@@ -5,10 +5,9 @@
  *
  * GPL LICENSE SUMMARY
  *
- * Copyright(c) 2012 - 2014 Intel Corporation. All rights reserved.
  * Copyright(c) 2013 - 2015 Intel Mobile Communications GmbH
  * Copyright(c) 2016 - 2017 Intel Deutschland GmbH
- * Copyright(c) 2018 - 2019 Intel Corporation
+ * Copyright(c) 2012 - 2014, 2018 - 2020 Intel Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of version 2 of the GNU General Public License as
@@ -28,10 +27,9 @@
  *
  * BSD LICENSE
  *
- * Copyright(c) 2012 - 2014 Intel Corporation. All rights reserved.
  * Copyright(c) 2013 - 2015 Intel Mobile Communications GmbH
  * Copyright(c) 2016 - 2017 Intel Deutschland GmbH
- * Copyright(c) 2018 - 2019 Intel Corporation
+ * Copyright(c) 2012 - 2014, 2018 - 2020 Intel Corporation
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -481,6 +479,11 @@ static ssize_t iwl_dbgfs_amsdu_len_write(struct ieee80211_sta *sta,
 	if (kstrtou16(buf, 0, &amsdu_len))
 		return -EINVAL;
 
+	/* only change from debug set <-> debug unset */
+	if ((amsdu_len && mvmsta->orig_amsdu_len) ||
+	    (!!amsdu_len && mvmsta->orig_amsdu_len))
+		return -EBUSY;
+
 	if (amsdu_len) {
 		mvmsta->orig_amsdu_len = sta->max_amsdu_len;
 		sta->max_amsdu_len = amsdu_len;

drivers/net/wireless/intel/iwlwifi/mvm/rs-fw.c

@@ -369,14 +369,15 @@ void iwl_mvm_tlc_update_notif(struct iwl_mvm *mvm,
 		u16 size = le32_to_cpu(notif->amsdu_size);
 		int i;
 
+		if (sta->max_amsdu_len < size) {
 			/*
 			 * In debug sta->max_amsdu_len < size
-		 * so also check with orig_amsdu_len which holds the original
-		 * data before debugfs changed the value
+			 * so also check with orig_amsdu_len which holds the
+			 * original data before debugfs changed the value
 			 */
-		if (WARN_ON(sta->max_amsdu_len < size &&
-			    mvmsta->orig_amsdu_len < size))
+			WARN_ON(mvmsta->orig_amsdu_len < size);
 			goto out;
+		}
 
 		mvmsta->amsdu_enabled = le32_to_cpu(notif->amsdu_enabled);
 		mvmsta->max_amsdu_len = size;