iwlwifi: mvm: allow to limit the A-MSDU from debugfs

in order to be able to tune the size of the desired A-MSDU
based on link condition, add a knob to modify the length
of the A-MSDU.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

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

@@ -64,6 +64,7 @@
  *
  *****************************************************************************/
 #include <linux/vmalloc.h>
+#include <linux/ieee80211.h>
 
 #include "mvm.h"
 #include "fw-dbg.h"
@@ -1080,6 +1081,22 @@ static ssize_t iwl_dbgfs_fw_dbg_collect_write(struct iwl_mvm *mvm,
 	return count;
 }
 
+static ssize_t iwl_dbgfs_max_amsdu_len_write(struct iwl_mvm *mvm,
+					     char *buf, size_t count,
+					     loff_t *ppos)
+{
+	unsigned int max_amsdu_len;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &max_amsdu_len);
+
+	if (max_amsdu_len > IEEE80211_MAX_MPDU_LEN_VHT_11454)
+		return -EINVAL;
+	mvm->max_amsdu_len = max_amsdu_len;
+
+	return count;
+}
+
 #define ADD_TEXT(...) pos += scnprintf(buf + pos, bufsz - pos, __VA_ARGS__)
 #ifdef CONFIG_IWLWIFI_BCAST_FILTERING
 static ssize_t iwl_dbgfs_bcast_filters_read(struct file *file,
@@ -1497,6 +1514,7 @@ MVM_DEBUGFS_READ_WRITE_FILE_OPS(d0i3_refs, 8);
 MVM_DEBUGFS_READ_WRITE_FILE_OPS(fw_dbg_conf, 8);
 MVM_DEBUGFS_WRITE_FILE_OPS(fw_dbg_collect, 64);
 MVM_DEBUGFS_WRITE_FILE_OPS(cont_recording, 8);
+MVM_DEBUGFS_WRITE_FILE_OPS(max_amsdu_len, 8);
 MVM_DEBUGFS_WRITE_FILE_OPS(indirection_tbl,
 			   (IWL_RSS_INDIRECTION_TABLE_SIZE * 2));
 
@@ -1541,6 +1559,7 @@ int iwl_mvm_dbgfs_register(struct iwl_mvm *mvm, struct dentry *dbgfs_dir)
 	MVM_DEBUGFS_ADD_FILE(d0i3_refs, mvm->debugfs_dir, S_IRUSR | S_IWUSR);
 	MVM_DEBUGFS_ADD_FILE(fw_dbg_conf, mvm->debugfs_dir, S_IRUSR | S_IWUSR);
 	MVM_DEBUGFS_ADD_FILE(fw_dbg_collect, mvm->debugfs_dir, S_IWUSR);
+	MVM_DEBUGFS_ADD_FILE(max_amsdu_len, mvm->debugfs_dir, S_IWUSR);
 	MVM_DEBUGFS_ADD_FILE(send_echo_cmd, mvm->debugfs_dir, S_IWUSR);
 	MVM_DEBUGFS_ADD_FILE(cont_recording, mvm->debugfs_dir, S_IWUSR);
 	MVM_DEBUGFS_ADD_FILE(indirection_tbl, mvm->debugfs_dir, S_IWUSR);

drivers/net/wireless/intel/iwlwifi/mvm/mvm.h

@@ -861,6 +861,7 @@ struct iwl_mvm {
 
 	/* Indicate if device power save is allowed */
 	u8 ps_disabled; /* u8 instead of bool to ease debugfs_create_* usage */
+	unsigned int max_amsdu_len; /* used for debugfs only */
 
 	struct ieee80211_vif __rcu *csa_vif;
 	struct ieee80211_vif __rcu *csa_tx_blocked_vif;

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

@@ -448,6 +448,7 @@ static int iwl_mvm_tx_tso(struct iwl_mvm *mvm, struct sk_buff *skb,
 	bool ipv4 = (skb->protocol == htons(ETH_P_IP));
 	u16 ip_base_id = ipv4 ? ntohs(ip_hdr(skb)->id) : 0;
 	u16 amsdu_add, snap_ip_tcp, pad, i = 0;
+	unsigned int dbg_max_amsdu_len;
 	u8 *qc, tid;
 
 	snap_ip_tcp = 8 + skb_transport_header(skb) - skb_network_header(skb) +
@@ -477,6 +478,10 @@ static int iwl_mvm_tx_tso(struct iwl_mvm *mvm, struct sk_buff *skb,
 	}
 
 	max_amsdu_len = sta->max_amsdu_len;
+	dbg_max_amsdu_len = ACCESS_ONCE(mvm->max_amsdu_len);
+	if (dbg_max_amsdu_len)
+		max_amsdu_len = min_t(unsigned int, max_amsdu_len,
+				      dbg_max_amsdu_len);
 
 	/*
 	 * Limit A-MSDU in A-MPDU to 4095 bytes when VHT is not