[PATCH v2 2/2] rtl8xxxu: fill up txrate info for gen1 chips

[Chris Chiu <chris.chiu@canonical.com>]

RTL8188CUS/RTL8192CU(gen1) don't support rate adatptive report hence
no real txrate info can be retrieved. The vendor driver reports the
highest rate in HT capabilities from the IEs to avoid empty txrate.
This commit initiates the txrate information with the highest supported
rate negotiated with AP. The gen2 chip keeps update the txrate from
the rate adaptive reports, and gen1 chips at least have non-NULL txrate
after associated.

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

Changelog:
  v2:
   - Use the 'static const' for rtl8xxxu_legacy_ratetable[]

 .../wireless/realtek/rtl8xxxu/rtl8xxxu_core.c | 59 +++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
index d225a1257530..cc9d14e9c4c4 100644
--- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
+++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
@@ -4473,6 +4473,35 @@ void rtl8xxxu_gen1_init_aggregation(struct rtl8xxxu_priv *priv)
 	priv->rx_buf_aggregation = 1;
 }
 
+static const struct ieee80211_rate rtl8xxxu_legacy_ratetable[] = {
+	{.bitrate = 10, .hw_value = 0x00,},
+	{.bitrate = 20, .hw_value = 0x01,},
+	{.bitrate = 55, .hw_value = 0x02,},
+	{.bitrate = 110, .hw_value = 0x03,},
+	{.bitrate = 60, .hw_value = 0x04,},
+	{.bitrate = 90, .hw_value = 0x05,},
+	{.bitrate = 120, .hw_value = 0x06,},
+	{.bitrate = 180, .hw_value = 0x07,},
+	{.bitrate = 240, .hw_value = 0x08,},
+	{.bitrate = 360, .hw_value = 0x09,},
+	{.bitrate = 480, .hw_value = 0x0a,},
+	{.bitrate = 540, .hw_value = 0x0b,},
+};
+
+static void rtl8xxxu_desc_to_mcsrate(u16 rate, u8 *mcs, u8 *nss)
+{
+	if (rate <= DESC_RATE_54M)
+		return;
+
+	if (rate >= DESC_RATE_MCS0 && rate <= DESC_RATE_MCS15) {
+		if (rate < DESC_RATE_MCS8)
+			*nss = 1;
+		else
+			*nss = 2;
+		*mcs = rate - DESC_RATE_MCS0;
+	}
+}
+
 static void rtl8xxxu_set_basic_rates(struct rtl8xxxu_priv *priv, u32 rate_cfg)
 {
 	struct ieee80211_hw *hw = priv->hw;
@@ -4534,9 +4563,12 @@ rtl8xxxu_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	struct rtl8xxxu_priv *priv = hw->priv;
 	struct device *dev = &priv->udev->dev;
 	struct ieee80211_sta *sta;
+	struct rtl8xxxu_ra_report *rarpt;
 	u32 val32;
 	u8 val8;
 
+	rarpt = &priv->ra_report;
+
 	if (changed & BSS_CHANGED_ASSOC) {
 		dev_dbg(dev, "Changed ASSOC: %i!\n", bss_conf->assoc);
 
@@ -4545,6 +4577,10 @@ rtl8xxxu_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 		if (bss_conf->assoc) {
 			u32 ramask;
 			int sgi = 0;
+			u8 highest_rate;
+			u8 mcs = 0, nss = 0;
+			u32 bit_rate;
+
 
 			rcu_read_lock();
 			sta = ieee80211_find_sta(vif, bss_conf->bssid);
@@ -4569,6 +4605,29 @@ rtl8xxxu_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 				sgi = 1;
 			rcu_read_unlock();
 
+			highest_rate = fls(ramask) - 1;
+			if (highest_rate < DESC_RATE_MCS0) {
+				rarpt->txrate.legacy =
+				rtl8xxxu_legacy_ratetable[highest_rate].bitrate;
+			} else {
+				rtl8xxxu_desc_to_mcsrate(highest_rate,
+							 &mcs, &nss);
+				rarpt->txrate.flags |= RATE_INFO_FLAGS_MCS;
+
+				rarpt->txrate.mcs = mcs;
+				rarpt->txrate.nss = nss;
+
+				if (sgi) {
+					rarpt->txrate.flags |=
+						RATE_INFO_FLAGS_SHORT_GI;
+				}
+
+				rarpt->txrate.bw |= RATE_INFO_BW_20;
+			}
+			bit_rate = cfg80211_calculate_bitrate(&rarpt->txrate);
+			rarpt->bit_rate = bit_rate;
+			rarpt->desc_rate = highest_rate;
+
 			priv->vif = vif;
 			priv->rssi_level = RTL8XXXU_RATR_STA_INIT;
 
-- 
2.20.1