[RFC PATCH v3] rtl8xxxu: Improve TX performance of RTL8723BU on rtl8xxxu driver

[RFC PATCH v3] rtl8xxxu: Improve TX performance of RTL8723BU on rtl8xxxu driver

[Chris Chiu]

We have 3 laptops which connect the wifi by the same RTL8723BU.
The PCI VID/PID of the wifi chip is 10EC:B720 which is supported.
They have the same problem with the in-kernel rtl8xxxu driver, the
iperf (as a client to an ethernet-connected server) gets ~1Mbps.
Nevertheless, the signal strength is reported as around -40dBm,
which is quite good. From the wireshark capture, the tx rate for each
data and qos data packet is only 1Mbps. Compare to the driver from
https://github.com/lwfinger/rtl8723bu, the same iperf test gets ~12
Mbps or more. The signal strength is reported similarly around
-40dBm. That's why we want to improve.

After reading the source code of the rtl8xxxu driver and Larry's, the
major difference is that Larry's driver has a watchdog which will keep
monitoring the signal quality and updating the rate mask just like the
rtl8xxxu_gen2_update_rate_mask() does if signal quality changes.
And this kind of watchdog also exists in rtlwifi driver of some specific
chips, ex rtl8192ee, rtl8188ee, rtl8723ae, rtl8821ae...etc. They have
the same member function named dm_watchdog and will invoke the
corresponding dm_refresh_rate_adaptive_mask to adjust the tx rate
mask.

With this commit, the tx rate of each data and qos data packet will
be 39Mbps (MCS4) with the 0xF00000 as the tx rate mask. The 20th bit
to 23th bit means MCS4 to MCS7. It means that the firmware still picks
the lowest rate from the rate mask and explains why the tx rate of
data and qos data is always lowest 1Mbps because the default rate mask
passed is always 0xFFFFFFF ranges from the basic CCK rate, OFDM rate,
and MCS rate. However, with Larry's driver, the tx rate observed from
wireshark under the same condition is almost 65Mbps or 72Mbps.

I believe the firmware of RTL8723BU may need fix. And I think we
can still bring in the dm_watchdog as rtlwifi to improve from the
driver side. Please leave precious comments for my commits and
suggest what I can do better. Or suggest if there's any better idea
to fix this. Thanks.

Signed-off-by: Chris Chiu <chiu@endlessm.com>
---


Notes:
  v2:
   - Fix errors and warnings complained by checkpatch.pl
   - Replace data structure rate_adaptive by 2 member variables
   - Make rtl8xxxu_wireless_mode non-static
   - Runs refresh_rate_mask() only in station mode
  v3:
   - Remove ugly rtl8xxxu_watchdog data structure
   - Make sure only one vif exists


 .../net/wireless/realtek/rtl8xxxu/rtl8xxxu.h  |  49 ++++++
 .../realtek/rtl8xxxu/rtl8xxxu_8723b.c         | 145 ++++++++++++++++++
 .../wireless/realtek/rtl8xxxu/rtl8xxxu_core.c |  80 +++++++++-
 3 files changed, 273 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h
index 8828baf26e7b..42e9227f4d19 100644
--- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h
+++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu.h
@@ -1195,6 +1195,44 @@ struct rtl8723bu_c2h {
 
 struct rtl8xxxu_fileops;
 
+/*mlme related.*/
+enum wireless_mode {
+	WIRELESS_MODE_UNKNOWN = 0,
+	/* Sub-Element */
+	WIRELESS_MODE_B = BIT(0),
+	WIRELESS_MODE_G = BIT(1),
+	WIRELESS_MODE_A = BIT(2),
+	WIRELESS_MODE_N_24G = BIT(3),
+	WIRELESS_MODE_N_5G = BIT(4),
+	WIRELESS_AUTO = BIT(5),
+	WIRELESS_MODE_AC = BIT(6),
+	WIRELESS_MODE_MAX = 0x7F,
+};
+
+/* from rtlwifi/wifi.h */
+enum ratr_table_mode_new {
+	RATEID_IDX_BGN_40M_2SS = 0,
+	RATEID_IDX_BGN_40M_1SS = 1,
+	RATEID_IDX_BGN_20M_2SS_BN = 2,
+	RATEID_IDX_BGN_20M_1SS_BN = 3,
+	RATEID_IDX_GN_N2SS = 4,
+	RATEID_IDX_GN_N1SS = 5,
+	RATEID_IDX_BG = 6,
+	RATEID_IDX_G = 7,
+	RATEID_IDX_B = 8,
+	RATEID_IDX_VHT_2SS = 9,
+	RATEID_IDX_VHT_1SS = 10,
+	RATEID_IDX_MIX1 = 11,
+	RATEID_IDX_MIX2 = 12,
+	RATEID_IDX_VHT_3SS = 13,
+	RATEID_IDX_BGN_3SS = 14,
+};
+
+#define RTL8XXXU_RATR_STA_INIT 0
+#define RTL8XXXU_RATR_STA_HIGH 1
+#define RTL8XXXU_RATR_STA_MID  2
+#define RTL8XXXU_RATR_STA_LOW  3
+
 struct rtl8xxxu_priv {
 	struct ieee80211_hw *hw;
 	struct usb_device *udev;
@@ -1299,6 +1337,14 @@ struct rtl8xxxu_priv {
 	u8 pi_enabled:1;
 	u8 no_pape:1;
 	u8 int_buf[USB_INTR_CONTENT_LENGTH];
+	u8 ratr_index;
+	u8 rssi_level;
+	/*
+	 * Single virtual interface permitted since the driver supports STATION
+	 * mode only.
+	 */
+	struct ieee80211_vif *vif;
+	struct delayed_work ra_watchdog;
 };
 
 struct rtl8xxxu_rx_urb {
@@ -1335,6 +1381,8 @@ struct rtl8xxxu_fileops {
 			      bool ht40);
 	void (*update_rate_mask) (struct rtl8xxxu_priv *priv,
 				  u32 ramask, int sgi);
+	void (*refresh_rate_mask) (struct rtl8xxxu_priv *priv, int signal,
+				   struct ieee80211_sta *sta);
 	void (*report_connect) (struct rtl8xxxu_priv *priv,
 				u8 macid, bool connect);
 	void (*fill_txdesc) (struct ieee80211_hw *hw, struct ieee80211_hdr *hdr,
@@ -1445,6 +1493,7 @@ void rtl8xxxu_fill_txdesc_v2(struct ieee80211_hw *hw, struct ieee80211_hdr *hdr,
 			     struct rtl8xxxu_txdesc32 *tx_desc32, bool sgi,
 			     bool short_preamble, bool ampdu_enable,
 			     u32 rts_rate);
+u16 rtl8xxxu_wireless_mode(struct ieee80211_hw *hw, struct ieee80211_sta *sta);
 
 extern struct rtl8xxxu_fileops rtl8192cu_fops;
 extern struct rtl8xxxu_fileops rtl8192eu_fops;
diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c
index 26b674aca125..7a510bc22a60 100644
--- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c
+++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c
@@ -1645,6 +1645,150 @@ static void rtl8723bu_init_statistics(struct rtl8xxxu_priv *priv)
 	rtl8xxxu_write32(priv, REG_OFDM0_FA_RSTC, val32);
 }
 
+static u8 rtl8723b_signal_to_rssi(int signal)
+{
+	if (signal < -95)
+		signal = -95;
+	return (u8)(signal + 95);
+}
+
+static void rtl8723b_refresh_rate_mask(struct rtl8xxxu_priv *priv,
+				       int signal, struct ieee80211_sta *sta)
+{
+	struct ieee80211_hw *hw = priv->hw;
+	u16 wireless_mode;
+	u8 rssi_level, ratr_index;
+	u8 txbw_40mhz;
+	u8 rssi, rssi_thresh_high, rssi_thresh_low;
+
+	rssi_level = priv->rssi_level;
+	rssi = rtl8723b_signal_to_rssi(signal);
+	ratr_index = priv->ratr_index;
+	txbw_40mhz = (hw->conf.chandef.width == NL80211_CHAN_WIDTH_40) ? 1 : 0;
+
+	switch (rssi_level) {
+	case RTL8XXXU_RATR_STA_HIGH:
+		rssi_thresh_high = 50;
+		rssi_thresh_low = 20;
+		break;
+	case RTL8XXXU_RATR_STA_MID:
+		rssi_thresh_high = 55;
+		rssi_thresh_low = 20;
+		break;
+	case RTL8XXXU_RATR_STA_LOW:
+		rssi_thresh_high = 60;
+		rssi_thresh_low = 25;
+		break;
+	default:
+		rssi_thresh_high = 50;
+		rssi_thresh_low = 20;
+		break;
+	}
+
+	if (rssi > rssi_thresh_high)
+		rssi_level = RTL8XXXU_RATR_STA_HIGH;
+	else if (rssi > rssi_thresh_low)
+		rssi_level = RTL8XXXU_RATR_STA_MID;
+	else
+		rssi_level = RTL8XXXU_RATR_STA_LOW;
+
+	if (rssi_level != priv->rssi_level) {
+		int sgi = 0;
+		u32 rate_bitmap = 0;
+
+		rcu_read_lock();
+		rate_bitmap = (sta->supp_rates[0] & 0xfff) |
+				(sta->ht_cap.mcs.rx_mask[0] << 12) |
+				(sta->ht_cap.mcs.rx_mask[1] << 20);
+		if (sta->ht_cap.cap &
+		    (IEEE80211_HT_CAP_SGI_40 | IEEE80211_HT_CAP_SGI_20))
+			sgi = 1;
+		rcu_read_unlock();
+
+		wireless_mode = rtl8xxxu_wireless_mode(hw, sta);
+		switch (wireless_mode) {
+		case WIRELESS_MODE_B:
+			ratr_index = RATEID_IDX_B;
+			if (rate_bitmap & 0x0000000c)
+				rate_bitmap &= 0x0000000d;
+			else
+				rate_bitmap &= 0x0000000f;
+			break;
+		case WIRELESS_MODE_A:
+		case WIRELESS_MODE_G:
+			ratr_index = RATEID_IDX_G;
+			if (rssi_level == RTL8XXXU_RATR_STA_HIGH)
+				rate_bitmap &= 0x00000f00;
+			else
+				rate_bitmap &= 0x00000ff0;
+			break;
+		case (WIRELESS_MODE_B | WIRELESS_MODE_G):
+			ratr_index = RATEID_IDX_BG;
+			if (rssi_level == RTL8XXXU_RATR_STA_HIGH)
+				rate_bitmap &= 0x00000f00;
+			else if (rssi_level == RTL8XXXU_RATR_STA_MID)
+				rate_bitmap &= 0x00000ff0;
+			else
+				rate_bitmap &= 0x00000ff5;
+			break;
+		case WIRELESS_MODE_N_24G:
+		case WIRELESS_MODE_N_5G:
+		case (WIRELESS_MODE_G | WIRELESS_MODE_N_24G):
+		case (WIRELESS_MODE_A | WIRELESS_MODE_N_5G):
+			if (priv->tx_paths == 2 && priv->rx_paths == 2)
+				ratr_index = RATEID_IDX_GN_N2SS;
+			else
+				ratr_index = RATEID_IDX_GN_N1SS;
+		case (WIRELESS_MODE_B | WIRELESS_MODE_G | WIRELESS_MODE_N_24G):
+		case (WIRELESS_MODE_B | WIRELESS_MODE_N_24G):
+			if (txbw_40mhz) {
+				if (priv->tx_paths == 2 && priv->rx_paths == 2)
+					ratr_index = RATEID_IDX_BGN_40M_2SS;
+				else
+					ratr_index = RATEID_IDX_BGN_40M_1SS;
+			} else {
+				if (priv->tx_paths == 2 && priv->rx_paths == 2)
+					ratr_index = RATEID_IDX_BGN_20M_2SS_BN;
+				else
+					ratr_index = RATEID_IDX_BGN_20M_1SS_BN;
+			}
+
+			if (priv->tx_paths == 2 && priv->rx_paths == 2) {
+				if (rssi_level == RTL8XXXU_RATR_STA_HIGH) {
+					rate_bitmap &= 0x0f8f0000;
+				} else if (rssi_level == RTL8XXXU_RATR_STA_MID) {
+					rate_bitmap &= 0x0f8ff000;
+				} else {
+					if (txbw_40mhz)
+						rate_bitmap &= 0x0f8ff015;
+					else
+						rate_bitmap &= 0x0f8ff005;
+				}
+			} else {
+				if (rssi_level == RTL8XXXU_RATR_STA_HIGH) {
+					rate_bitmap &= 0x000f0000;
+				} else if (rssi_level == RTL8XXXU_RATR_STA_MID) {
+					rate_bitmap &= 0x000ff000;
+				} else {
+					if (txbw_40mhz)
+						rate_bitmap &= 0x000ff015;
+					else
+						rate_bitmap &= 0x000ff005;
+				}
+			}
+			break;
+		default:
+			ratr_index = RATEID_IDX_BGN_40M_2SS;
+			rate_bitmap &= 0x0fffffff;
+			break;
+		}
+
+		priv->ratr_index = ratr_index;
+		priv->rssi_level = rssi_level;
+		priv->fops->update_rate_mask(priv, rate_bitmap, sgi);
+	}
+}
+
 struct rtl8xxxu_fileops rtl8723bu_fops = {
 	.parse_efuse = rtl8723bu_parse_efuse,
 	.load_firmware = rtl8723bu_load_firmware,
@@ -1665,6 +1809,7 @@ struct rtl8xxxu_fileops rtl8723bu_fops = {
 	.usb_quirks = rtl8xxxu_gen2_usb_quirks,
 	.set_tx_power = rtl8723b_set_tx_power,
 	.update_rate_mask = rtl8xxxu_gen2_update_rate_mask,
+	.refresh_rate_mask = rtl8723b_refresh_rate_mask,
 	.report_connect = rtl8xxxu_gen2_report_connect,
 	.fill_txdesc = rtl8xxxu_fill_txdesc_v2,
 	.writeN_block_size = 1024,
diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
index 039e5ca9d2e4..2d612c2df5b2 100644
--- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
+++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
@@ -4345,7 +4345,7 @@ void rtl8xxxu_gen2_update_rate_mask(struct rtl8xxxu_priv *priv,
 	h2c.b_macid_cfg.ramask3 = (ramask >> 24) & 0xff;
 
 	h2c.ramask.arg = 0x80;
-	h2c.b_macid_cfg.data1 = 0;
+	h2c.b_macid_cfg.data1 = priv->ratr_index;
 	if (sgi)
 		h2c.b_macid_cfg.data1 |= BIT(7);
 
@@ -4485,6 +4485,40 @@ static void rtl8xxxu_set_basic_rates(struct rtl8xxxu_priv *priv, u32 rate_cfg)
 	rtl8xxxu_write8(priv, REG_INIRTS_RATE_SEL, rate_idx);
 }
 
+u16
+rtl8xxxu_wireless_mode(struct ieee80211_hw *hw, struct ieee80211_sta *sta)
+{
+	u16 network_type = WIRELESS_MODE_UNKNOWN;
+	u32 rate_mask;
+
+	rate_mask = (sta->supp_rates[0] & 0xfff) |
+		    (sta->ht_cap.mcs.rx_mask[0] << 12) |
+		    (sta->ht_cap.mcs.rx_mask[0] << 20);
+
+	if (hw->conf.chandef.chan->band == NL80211_BAND_5GHZ) {
+		if (sta->vht_cap.vht_supported)
+			network_type = WIRELESS_MODE_AC;
+		else if (sta->ht_cap.ht_supported)
+			network_type = WIRELESS_MODE_N_5G;
+
+		network_type |= WIRELESS_MODE_A;
+	} else {
+		if (sta->vht_cap.vht_supported)
+			network_type = WIRELESS_MODE_AC;
+		else if (sta->ht_cap.ht_supported)
+			network_type = WIRELESS_MODE_N_24G;
+
+		if (sta->supp_rates[0] <= 0xf)
+			network_type |= WIRELESS_MODE_B;
+		else if (sta->supp_rates[0] & 0xf)
+			network_type |= (WIRELESS_MODE_B | WIRELESS_MODE_G);
+		else
+			network_type |= WIRELESS_MODE_G;
+	}
+
+	return network_type;
+}
+
 static void
 rtl8xxxu_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 			  struct ieee80211_bss_conf *bss_conf, u32 changed)
@@ -4527,6 +4561,10 @@ rtl8xxxu_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 				sgi = 1;
 			rcu_read_unlock();
 
+			priv->vif = vif;
+			priv->ratr_index = RATEID_IDX_BGN_40M_2SS;
+			priv->rssi_level = RTL8XXXU_RATR_STA_INIT;
+
 			priv->fops->update_rate_mask(priv, ramask, sgi);
 
 			rtl8xxxu_write8(priv, REG_BCN_MAX_ERR, 0xff);
@@ -5471,6 +5509,10 @@ static int rtl8xxxu_add_interface(struct ieee80211_hw *hw,
 
 	switch (vif->type) {
 	case NL80211_IFTYPE_STATION:
+		if (!priv->vif)
+			priv->vif = vif;
+		else
+			return -EOPNOTSUPP;
 		rtl8xxxu_stop_tx_beacon(priv);
 
 		val8 = rtl8xxxu_read8(priv, REG_BEACON_CTRL);
@@ -5779,6 +5821,37 @@ rtl8xxxu_ampdu_action(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	return 0;
 }
 
+static void rtl8xxxu_watchdog_callback(struct work_struct *work)
+{
+	struct ieee80211_vif *vif;
+	struct rtl8xxxu_priv *priv;
+
+	priv = container_of(work, struct rtl8xxxu_priv, ra_watchdog.work);
+	vif = priv->vif;
+
+	if (vif && vif->type == NL80211_IFTYPE_STATION) {
+		int signal;
+		struct ieee80211_sta *sta;
+
+		rcu_read_lock();
+		sta = ieee80211_find_sta(vif, vif->bss_conf.bssid);
+		if (!sta) {
+			struct device *dev = &priv->udev->dev;
+
+			dev_info(dev, "%s: no sta found\n", __func__);
+			rcu_read_unlock();
+			return;
+		}
+		rcu_read_unlock();
+
+		signal = ieee80211_ave_rssi(vif);
+		if (priv->fops->refresh_rate_mask)
+			priv->fops->refresh_rate_mask(priv, signal, sta);
+	}
+
+	schedule_delayed_work(&priv->ra_watchdog, 2 * HZ);
+}
+
 static int rtl8xxxu_start(struct ieee80211_hw *hw)
 {
 	struct rtl8xxxu_priv *priv = hw->priv;
@@ -5835,6 +5908,8 @@ static int rtl8xxxu_start(struct ieee80211_hw *hw)
 
 		ret = rtl8xxxu_submit_rx_urb(priv, rx_urb);
 	}
+
+	schedule_delayed_work(&priv->ra_watchdog, 2 * HZ);
 exit:
 	/*
 	 * Accept all data and mgmt frames
@@ -6058,6 +6133,7 @@ static int rtl8xxxu_probe(struct usb_interface *interface,
 	INIT_LIST_HEAD(&priv->rx_urb_pending_list);
 	spin_lock_init(&priv->rx_urb_lock);
 	INIT_WORK(&priv->rx_urb_wq, rtl8xxxu_rx_urb_work);
+	INIT_DELAYED_WORK(&priv->ra_watchdog, rtl8xxxu_watchdog_callback);
 
 	usb_set_intfdata(interface, hw);
 
@@ -6183,6 +6259,8 @@ static void rtl8xxxu_disconnect(struct usb_interface *interface)
 	mutex_destroy(&priv->usb_buf_mutex);
 	mutex_destroy(&priv->h2c_mutex);
 
+	cancel_delayed_work_sync(&priv->ra_watchdog);
+
 	if (priv->udev->state != USB_STATE_NOTATTACHED) {
 		dev_info(&priv->udev->dev,
 			 "Device still attached, trying to reset\n");
-- 
2.21.0

Re: [RFC PATCH v3] rtl8xxxu: Improve TX performance of RTL8723BU on rtl8xxxu driver

[Daniel Drake]

Hi Chris,

On Tue, May 28, 2019 at 11:03 PM Chris Chiu <chiu@endlessm.com> wrote:
> +       /*
> +        * Single virtual interface permitted since the driver supports STATION
> +        * mode only.

I think you can be a bit more explicit by saying e.g.:

Only one virtual interface permitted because only STA mode is
supported and no iface_combinations are provided.

> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> index 039e5ca9d2e4..2d612c2df5b2 100644
> --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> @@ -4345,7 +4345,7 @@ void rtl8xxxu_gen2_update_rate_mask(struct rtl8xxxu_priv *priv,
>         h2c.b_macid_cfg.ramask3 = (ramask >> 24) & 0xff;
>
>         h2c.ramask.arg = 0x80;
> -       h2c.b_macid_cfg.data1 = 0;
> +       h2c.b_macid_cfg.data1 = priv->ratr_index;

I think ratr_index can be moved to be a function parameter of the
update_rate_mask function. It looks like all callsites already know
which value they want to set. Then you don't have to store it in the
priv structure.

> @@ -5471,6 +5509,10 @@ static int rtl8xxxu_add_interface(struct ieee80211_hw *hw,
>
>         switch (vif->type) {
>         case NL80211_IFTYPE_STATION:
> +               if (!priv->vif)
> +                       priv->vif = vif;
> +               else
> +                       return -EOPNOTSUPP;
>                 rtl8xxxu_stop_tx_beacon(priv);

rtl8xxxu_remove_interface should also set priv->vif back to NULL.

> @@ -6183,6 +6259,8 @@ static void rtl8xxxu_disconnect(struct usb_interface *interface)
>         mutex_destroy(&priv->usb_buf_mutex);
>         mutex_destroy(&priv->h2c_mutex);
>
> +       cancel_delayed_work_sync(&priv->ra_watchdog);

Given that the work was started in rtl8xxxu_start, I think it should
be cancelled in rtl8xxxu_stop() instead.

Daniel

Re: [RFC PATCH v3] rtl8xxxu: Improve TX performance of RTL8723BU on rtl8xxxu driver

[Larry Finger]

On 5/29/19 12:03 AM, Chris Chiu wrote:
> We have 3 laptops which connect the wifi by the same RTL8723BU.
> The PCI VID/PID of the wifi chip is 10EC:B720 which is supported.
> They have the same problem with the in-kernel rtl8xxxu driver, the
> iperf (as a client to an ethernet-connected server) gets ~1Mbps.
> Nevertheless, the signal strength is reported as around -40dBm,
> which is quite good. From the wireshark capture, the tx rate for each
> data and qos data packet is only 1Mbps. Compare to the driver from
> https://github.com/lwfinger/rtl8723bu, the same iperf test gets ~12
> Mbps or more. The signal strength is reported similarly around
> -40dBm. That's why we want to improve.

The driver at GitHub was written by Realtek. I only published it in a prominent 
location, and fix it for kernel API changes. I would say "the Realtek driver at 
https://...", and every mention of "Larry's driver" should say "Realtek's 
driver". That attribution is more correct.
> 
> After reading the source code of the rtl8xxxu driver and Larry's, the
> major difference is that Larry's driver has a watchdog which will keep
> monitoring the signal quality and updating the rate mask just like the
> rtl8xxxu_gen2_update_rate_mask() does if signal quality changes.
> And this kind of watchdog also exists in rtlwifi driver of some specific
> chips, ex rtl8192ee, rtl8188ee, rtl8723ae, rtl8821ae...etc. They have
> the same member function named dm_watchdog and will invoke the
> corresponding dm_refresh_rate_adaptive_mask to adjust the tx rate
> mask.
> 
> With this commit, the tx rate of each data and qos data packet will
> be 39Mbps (MCS4) with the 0xF00000 as the tx rate mask. The 20th bit
> to 23th bit means MCS4 to MCS7. It means that the firmware still picks
> the lowest rate from the rate mask and explains why the tx rate of
> data and qos data is always lowest 1Mbps because the default rate mask
> passed is always 0xFFFFFFF ranges from the basic CCK rate, OFDM rate,
> and MCS rate. However, with Larry's driver, the tx rate observed from
> wireshark under the same condition is almost 65Mbps or 72Mbps.
> 
> I believe the firmware of RTL8723BU may need fix. And I think we
> can still bring in the dm_watchdog as rtlwifi to improve from the
> driver side. Please leave precious comments for my commits and
> suggest what I can do better. Or suggest if there's any better idea
> to fix this. Thanks.
> 
> Signed-off-by: Chris Chiu <chiu@endlessm.com>

I have not tested this patch, but I plan to soon.

Larry

Re: [RFC PATCH v3] rtl8xxxu: Improve TX performance of RTL8723BU on rtl8xxxu driver

[Chris Chiu]

On Thu, May 30, 2019 at 2:12 AM Daniel Drake <drake@endlessm.com> wrote:
>
> Hi Chris,
>
> On Tue, May 28, 2019 at 11:03 PM Chris Chiu <chiu@endlessm.com> wrote:
> > +       /*
> > +        * Single virtual interface permitted since the driver supports STATION
> > +        * mode only.
>
> I think you can be a bit more explicit by saying e.g.:
>
> Only one virtual interface permitted because only STA mode is
> supported and no iface_combinations are provided.
>
> > diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> > index 039e5ca9d2e4..2d612c2df5b2 100644
> > --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> > +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> > @@ -4345,7 +4345,7 @@ void rtl8xxxu_gen2_update_rate_mask(struct rtl8xxxu_priv *priv,
> >         h2c.b_macid_cfg.ramask3 = (ramask >> 24) & 0xff;
> >
> >         h2c.ramask.arg = 0x80;
> > -       h2c.b_macid_cfg.data1 = 0;
> > +       h2c.b_macid_cfg.data1 = priv->ratr_index;
>
> I think ratr_index can be moved to be a function parameter of the
> update_rate_mask function. It looks like all callsites already know
> which value they want to set. Then you don't have to store it in the
> priv structure.
>

You mean moving the ratr_index to be the 4th function parameter of
update_rate_mask which has 2 candidates rtl8xxxu_update_rate_mask
and rtl8xxxu_gen2_update_rate_mask? I was planning to keep the
rtl8xxxu_update_rate_mask the same because old chips seems don't
need the rate index when invoking H2C command to change rate mask.
And rate index is not a common phrase/term for rate adaptive. Theoretically
we just need packet error rate, sgi and other factors to determine the rate
mask. This rate index seems to be only specific to newer Realtek drivers
or firmware for rate adaptive algorithm.  I'd like to keep this for gen2 but
I admit it's ugly to put it in the priv structure. Any suggestion is
appreciated.
Thanks

> > @@ -5471,6 +5509,10 @@ static int rtl8xxxu_add_interface(struct ieee80211_hw *hw,
> >
> >         switch (vif->type) {
> >         case NL80211_IFTYPE_STATION:
> > +               if (!priv->vif)
> > +                       priv->vif = vif;
> > +               else
> > +                       return -EOPNOTSUPP;
> >                 rtl8xxxu_stop_tx_beacon(priv);
>
> rtl8xxxu_remove_interface should also set priv->vif back to NULL.
>
> > @@ -6183,6 +6259,8 @@ static void rtl8xxxu_disconnect(struct usb_interface *interface)
> >         mutex_destroy(&priv->usb_buf_mutex);
> >         mutex_destroy(&priv->h2c_mutex);
> >
> > +       cancel_delayed_work_sync(&priv->ra_watchdog);
>
> Given that the work was started in rtl8xxxu_start, I think it should
> be cancelled in rtl8xxxu_stop() instead.
>
> Daniel

Re: [RFC PATCH v3] rtl8xxxu: Improve TX performance of RTL8723BU on rtl8xxxu driver

[Chris Chiu]

On Thu, May 30, 2019 at 2:22 AM Larry Finger <Larry.Finger@lwfinger.net> wrote:
>
> On 5/29/19 12:03 AM, Chris Chiu wrote:
> > We have 3 laptops which connect the wifi by the same RTL8723BU.
> > The PCI VID/PID of the wifi chip is 10EC:B720 which is supported.
> > They have the same problem with the in-kernel rtl8xxxu driver, the
> > iperf (as a client to an ethernet-connected server) gets ~1Mbps.
> > Nevertheless, the signal strength is reported as around -40dBm,
> > which is quite good. From the wireshark capture, the tx rate for each
> > data and qos data packet is only 1Mbps. Compare to the driver from
> > https://github.com/lwfinger/rtl8723bu, the same iperf test gets ~12
> > Mbps or more. The signal strength is reported similarly around
> > -40dBm. That's why we want to improve.
>
> The driver at GitHub was written by Realtek. I only published it in a prominent
> location, and fix it for kernel API changes. I would say "the Realtek driver at
> https://...", and every mention of "Larry's driver" should say "Realtek's
> driver". That attribution is more correct.

Thanks. I'll modify this in next revision.

> >
> > After reading the source code of the rtl8xxxu driver and Larry's, the
> > major difference is that Larry's driver has a watchdog which will keep
> > monitoring the signal quality and updating the rate mask just like the
> > rtl8xxxu_gen2_update_rate_mask() does if signal quality changes.
> > And this kind of watchdog also exists in rtlwifi driver of some specific
> > chips, ex rtl8192ee, rtl8188ee, rtl8723ae, rtl8821ae...etc. They have
> > the same member function named dm_watchdog and will invoke the
> > corresponding dm_refresh_rate_adaptive_mask to adjust the tx rate
> > mask.
> >
> > With this commit, the tx rate of each data and qos data packet will
> > be 39Mbps (MCS4) with the 0xF00000 as the tx rate mask. The 20th bit
> > to 23th bit means MCS4 to MCS7. It means that the firmware still picks
> > the lowest rate from the rate mask and explains why the tx rate of
> > data and qos data is always lowest 1Mbps because the default rate mask
> > passed is always 0xFFFFFFF ranges from the basic CCK rate, OFDM rate,
> > and MCS rate. However, with Larry's driver, the tx rate observed from
> > wireshark under the same condition is almost 65Mbps or 72Mbps.
> >
> > I believe the firmware of RTL8723BU may need fix. And I think we
> > can still bring in the dm_watchdog as rtlwifi to improve from the
> > driver side. Please leave precious comments for my commits and
> > suggest what I can do better. Or suggest if there's any better idea
> > to fix this. Thanks.
> >
> > Signed-off-by: Chris Chiu <chiu@endlessm.com>
>
> I have not tested this patch, but I plan to soon.
>
> Larry
>
>

Re: [RFC PATCH v3] rtl8xxxu: Improve TX performance of RTL8723BU on rtl8xxxu driver

[Daniel Drake]

On Wed, May 29, 2019 at 10:52 PM Chris Chiu <chiu@endlessm.com> wrote:
> You mean moving the ratr_index to be the 4th function parameter of
> update_rate_mask which has 2 candidates rtl8xxxu_update_rate_mask
> and rtl8xxxu_gen2_update_rate_mask? I was planning to keep the
> rtl8xxxu_update_rate_mask the same because old chips seems don't
> need the rate index when invoking H2C command to change rate mask.
> And rate index is not a common phrase/term for rate adaptive. Theoretically
> we just need packet error rate, sgi and other factors to determine the rate
> mask. This rate index seems to be only specific to newer Realtek drivers
> or firmware for rate adaptive algorithm.  I'd like to keep this for gen2 but
> I admit it's ugly to put it in the priv structure. Any suggestion is
> appreciated.

I think it's cleaner to have it as a function parameter, even if the
old chips don't use it.
The rest of the implementation is in the core, so we aren't exactly
dealing with chip-specific code here, at least the way it's currently
done.
The vendor driver also has it as a function parameter from what I can see.

Daniel