rtw88: add debugfs to force lowest basic rate

The management frame with high rate e.g. 24M may not be transmitted
smoothly in long range environment.
Add a debugfs to force to use the lowest basic rate
in order to debug the reachability of transmitting management frame.

obtain current setting
cat /sys/kernel/debug/ieee80211/phyX/rtw88/force_lowest_basic_rate

force lowest rate:
echo 1 > /sys/kernel/debug/ieee80211/phyX/rtw88/force_lowest_basic_rate
Signed-off-by: Yu-Yen Ting <steventing@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211102022454.10944-2-pkshih@realtek.com

drivers/net/wireless/realtek/rtw88/debug.c

@@ -904,6 +904,39 @@ static int rtw_debugfs_get_fw_crash(struct seq_file *m, void *v)
 	return 0;
 }
 
+static ssize_t rtw_debugfs_set_force_lowest_basic_rate(struct file *filp,
+						       const char __user *buffer,
+						       size_t count, loff_t *loff)
+{
+	struct seq_file *seqpriv = (struct seq_file *)filp->private_data;
+	struct rtw_debugfs_priv *debugfs_priv = seqpriv->private;
+	struct rtw_dev *rtwdev = debugfs_priv->rtwdev;
+	bool input;
+	int err;
+
+	err = kstrtobool_from_user(buffer, count, &input);
+	if (err)
+		return err;
+
+	if (input)
+		set_bit(RTW_FLAG_FORCE_LOWEST_RATE, rtwdev->flags);
+	else
+		clear_bit(RTW_FLAG_FORCE_LOWEST_RATE, rtwdev->flags);
+
+	return count;
+}
+
+static int rtw_debugfs_get_force_lowest_basic_rate(struct seq_file *m, void *v)
+{
+	struct rtw_debugfs_priv *debugfs_priv = m->private;
+	struct rtw_dev *rtwdev = debugfs_priv->rtwdev;
+
+	seq_printf(m, "force lowest basic rate: %d\n",
+		   test_bit(RTW_FLAG_FORCE_LOWEST_RATE, rtwdev->flags));
+
+	return 0;
+}
+
 static ssize_t rtw_debugfs_set_dm_cap(struct file *filp,
 				      const char __user *buffer,
 				      size_t count, loff_t *loff)
@@ -1094,6 +1127,11 @@ static struct rtw_debugfs_priv rtw_debug_priv_fw_crash = {
 	.cb_read = rtw_debugfs_get_fw_crash,
 };
 
+static struct rtw_debugfs_priv rtw_debug_priv_force_lowest_basic_rate = {
+	.cb_write = rtw_debugfs_set_force_lowest_basic_rate,
+	.cb_read = rtw_debugfs_get_force_lowest_basic_rate,
+};
+
 static struct rtw_debugfs_priv rtw_debug_priv_dm_cap = {
 	.cb_write = rtw_debugfs_set_dm_cap,
 	.cb_read = rtw_debugfs_get_dm_cap,
@@ -1174,6 +1212,7 @@ void rtw_debugfs_init(struct rtw_dev *rtwdev)
 	rtw_debugfs_add_r(tx_pwr_tbl);
 	rtw_debugfs_add_rw(edcca_enable);
 	rtw_debugfs_add_rw(fw_crash);
+	rtw_debugfs_add_rw(force_lowest_basic_rate);
 	rtw_debugfs_add_rw(dm_cap);
 }
 

drivers/net/wireless/realtek/rtw88/main.h

@@ -364,6 +364,7 @@ enum rtw_flags {
 	RTW_FLAG_WOWLAN,
 	RTW_FLAG_RESTARTING,
 	RTW_FLAG_RESTART_TRIGGERING,
+	RTW_FLAG_FORCE_LOWEST_RATE,
 
 	NUM_OF_RTW_FLAGS,
 };

drivers/net/wireless/realtek/rtw88/tx.c

@@ -238,8 +238,9 @@ static u8 rtw_get_mgmt_rate(struct rtw_dev *rtwdev, struct sk_buff *skb,
 {
 	struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
 	struct ieee80211_vif *vif = tx_info->control.vif;
+	bool force_lowest = test_bit(RTW_FLAG_FORCE_LOWEST_RATE, rtwdev->flags);
 
-	if (!vif || !vif->bss_conf.basic_rates || ignore_rate)
+	if (!vif || !vif->bss_conf.basic_rates || ignore_rate || force_lowest)
 		return lowest_rate;
 
 	return __ffs(vif->bss_conf.basic_rates) + lowest_rate;