add mt7601u driver

Add support for the simplest of MediaTek Wi-Fi devices - MT7601U.
It is a single stream bgn chip with no bells or whistles.
This driver is partially based on Felix's mt76 but IMHO it doesn't
make sense to merge the two right now because MT7601U is a design
somewhere between old Ralink devices and new Mediatek chips.  There
wouldn't be all that much code sharing with the devices mt76 supports.
Situation may obviously change when someone decides to extend m76 with
support for the more recent USB dongles.

The driver supports only station mode.  I'm hoping to add AP support
when time allows.

This driver sat on GitHub for quite a while and got some testing there:
http://github.com/kuba-moo/mt7601u

Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

1 files changed, 319 insertions, 0 deletions

diff --git a/drivers/net/wireless/mediatek/mt7601u/tx.c b/drivers/net/wireless/mediatek/mt7601u/tx.c
new file mode 100644
index 000000000000..0be2080ceab3
--- /dev/null
+++ b/drivers/net/wireless/mediatek/mt7601u/tx.c
@@ -0,0 +1,319 @@
+/*
+ * Copyright (C) 2014 Felix Fietkau <nbd@openwrt.org>
+ * Copyright (C) 2015 Jakub Kicinski <kubakici@wp.pl>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include "mt7601u.h"
+#include "trace.h"
+
+enum mt76_txq_id {
+	MT_TXQ_VO = IEEE80211_AC_VO,
+	MT_TXQ_VI = IEEE80211_AC_VI,
+	MT_TXQ_BE = IEEE80211_AC_BE,
+	MT_TXQ_BK = IEEE80211_AC_BK,
+	MT_TXQ_PSD,
+	MT_TXQ_MCU,
+	__MT_TXQ_MAX
+};
+
+/* Hardware uses mirrored order of queues with Q0 having the highest priority */
+static u8 q2hwq(u8 q)
+{
+	return q ^ 0x3;
+}
+
+/* Take mac80211 Q id from the skb and translate it to hardware Q id */
+static u8 skb2q(struct sk_buff *skb)
+{
+	int qid = skb_get_queue_mapping(skb);
+
+	if (WARN_ON(qid >= MT_TXQ_PSD)) {
+		qid = MT_TXQ_BE;
+		skb_set_queue_mapping(skb, qid);
+	}
+
+	return q2hwq(qid);
+}
+
+/* Note: TX retry reporting is a bit broken.
+ *	 Retries are reported only once per AMPDU and often come a frame early
+ *	 i.e. they are reported in the last status preceding the AMPDU. Apart
+ *	 from the fact that it's hard to know the length of the AMPDU (which is
+ *	 required to know to how many consecutive frames retries should be
+ *	 applied), if status comes early on full FIFO it gets lost and retries
+ *	 of the whole AMPDU become invisible.
+ *	 As a work-around encode the desired rate in PKT_ID of TX descriptor
+ *	 and based on that guess the retries (every rate is tried once).
+ *	 Only downside here is that for MCS0 we have to rely solely on
+ *	 transmission failures as no retries can ever be reported.
+ *	 Not having to read EXT_FIFO has a nice effect of doubling the number
+ *	 of reports which can be fetched.
+ *	 Also the vendor driver never uses the EXT_FIFO register so it may be
+ *	 undertested.
+ */
+static u8 mt7601u_tx_pktid_enc(struct mt7601u_dev *dev, u8 rate, bool is_probe)
+{
+	u8 encoded = (rate + 1) + is_probe *  8;
+
+	/* Because PKT_ID 0 disables status reporting only 15 values are
+	 * available but 16 are needed (8 MCS * 2 for encoding is_probe)
+	 * - we need to cram together two rates. MCS0 and MCS7 with is_probe
+	 * share PKT_ID 9.
+	 */
+	if (is_probe && rate == 7)
+		return encoded - 7;
+
+	return encoded;
+}
+
+static void
+mt7601u_tx_pktid_dec(struct mt7601u_dev *dev, struct mt76_tx_status *stat)
+{
+	u8 req_rate = stat->pktid;
+	u8 eff_rate = stat->rate & 0x7;
+
+	req_rate -= 1;
+
+	if (req_rate > 7) {
+		stat->is_probe = true;
+		req_rate -= 8;
+
+		/* Decide between MCS0 and MCS7 which share pktid 9 */
+		if (!req_rate && eff_rate)
+			req_rate = 7;
+	}
+
+	stat->retry = req_rate - eff_rate;
+}
+
+static void mt7601u_tx_skb_remove_dma_overhead(struct sk_buff *skb,
+					       struct ieee80211_tx_info *info)
+{
+	int pkt_len = (unsigned long)info->status.status_driver_data[0];
+
+	skb_pull(skb, sizeof(struct mt76_txwi) + 4);
+	if (ieee80211_get_hdrlen_from_skb(skb) % 4)
+		mt76_remove_hdr_pad(skb);
+
+	skb_trim(skb, pkt_len);
+}
+
+void mt7601u_tx_status(struct mt7601u_dev *dev, struct sk_buff *skb)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+
+	mt7601u_tx_skb_remove_dma_overhead(skb, info);
+
+	ieee80211_tx_info_clear_status(info);
+	info->status.rates[0].idx = -1;
+	info->flags |= IEEE80211_TX_STAT_ACK;
+	ieee80211_tx_status(dev->hw, skb);
+}
+
+static int mt7601u_skb_rooms(struct mt7601u_dev *dev, struct sk_buff *skb)
+{
+	int hdr_len = ieee80211_get_hdrlen_from_skb(skb);
+	u32 need_head;
+
+	need_head = sizeof(struct mt76_txwi) + 4;
+	if (hdr_len % 4)
+		need_head += 2;
+
+	return skb_cow(skb, need_head);
+}
+
+static struct mt76_txwi *
+mt7601u_push_txwi(struct mt7601u_dev *dev, struct sk_buff *skb,
+		  struct ieee80211_sta *sta, struct mt76_wcid *wcid,
+		  int pkt_len)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_tx_rate *rate = &info->control.rates[0];
+	struct mt76_txwi *txwi;
+	unsigned long flags;
+	bool is_probe;
+	u32 pkt_id;
+	u16 rate_ctl;
+	u8 nss;
+
+	txwi = (struct mt76_txwi *)skb_push(skb, sizeof(struct mt76_txwi));
+	memset(txwi, 0, sizeof(*txwi));
+
+	if (!wcid->tx_rate_set)
+		ieee80211_get_tx_rates(info->control.vif, sta, skb,
+				       info->control.rates, 1);
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (rate->idx < 0 || !rate->count)
+		rate_ctl = wcid->tx_rate;
+	else
+		rate_ctl = mt76_mac_tx_rate_val(dev, rate, &nss);
+	spin_unlock_irqrestore(&dev->lock, flags);
+	txwi->rate_ctl = cpu_to_le16(rate_ctl);
+
+	if (!(info->flags & IEEE80211_TX_CTL_NO_ACK))
+		txwi->ack_ctl |= MT_TXWI_ACK_CTL_REQ;
+	if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ)
+		txwi->ack_ctl |= MT_TXWI_ACK_CTL_NSEQ;
+
+	if ((info->flags & IEEE80211_TX_CTL_AMPDU) && sta) {
+		u8 ba_size = IEEE80211_MIN_AMPDU_BUF;
+
+		ba_size <<= sta->ht_cap.ampdu_factor;
+		ba_size = min_t(int, 63, ba_size);
+		if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
+			ba_size = 0;
+		txwi->ack_ctl |= MT76_SET(MT_TXWI_ACK_CTL_BA_WINDOW, ba_size);
+
+		txwi->flags = cpu_to_le16(MT_TXWI_FLAGS_AMPDU |
+					  MT76_SET(MT_TXWI_FLAGS_MPDU_DENSITY,
+						   sta->ht_cap.ampdu_density));
+		if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
+			txwi->flags = 0;
+	}
+
+	txwi->wcid = wcid->idx;
+
+	is_probe = !!(info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE);
+	pkt_id = mt7601u_tx_pktid_enc(dev, rate_ctl & 0x7, is_probe);
+	pkt_len |= MT76_SET(MT_TXWI_LEN_PKTID, pkt_id);
+	txwi->len_ctl = cpu_to_le16(pkt_len);
+
+	return txwi;
+}
+
+void mt7601u_tx(struct ieee80211_hw *hw, struct ieee80211_tx_control *control,
+		struct sk_buff *skb)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct mt7601u_dev *dev = hw->priv;
+	struct ieee80211_vif *vif = info->control.vif;
+	struct ieee80211_sta *sta = control->sta;
+	struct mt76_sta *msta = NULL;
+	struct mt76_wcid *wcid = dev->mon_wcid;
+	struct mt76_txwi *txwi;
+	int pkt_len = skb->len;
+	int hw_q = skb2q(skb);
+
+	BUILD_BUG_ON(ARRAY_SIZE(info->status.status_driver_data) < 1);
+	info->status.status_driver_data[0] = (void *)(unsigned long)pkt_len;
+
+	if (mt7601u_skb_rooms(dev, skb) || mt76_insert_hdr_pad(skb)) {
+		ieee80211_free_txskb(dev->hw, skb);
+		return;
+	}
+
+	if (sta) {
+		msta = (struct mt76_sta *) sta->drv_priv;
+		wcid = &msta->wcid;
+	} else if (vif) {
+		struct mt76_vif *mvif = (struct mt76_vif *)vif->drv_priv;
+
+		wcid = &mvif->group_wcid;
+	}
+
+	txwi = mt7601u_push_txwi(dev, skb, sta, wcid, pkt_len);
+
+	if (mt7601u_dma_enqueue_tx(dev, skb, wcid, hw_q))
+		return;
+
+	trace_mt_tx(dev, skb, msta, txwi);
+}
+
+void mt7601u_tx_stat(struct work_struct *work)
+{
+	struct mt7601u_dev *dev = container_of(work, struct mt7601u_dev,
+					       stat_work.work);
+	struct mt76_tx_status stat;
+	unsigned long flags;
+	int cleaned = 0;
+
+	while (!test_bit(MT7601U_STATE_REMOVED, &dev->state)) {
+		stat = mt7601u_mac_fetch_tx_status(dev);
+		if (!stat.valid)
+			break;
+
+		mt7601u_tx_pktid_dec(dev, &stat);
+		mt76_send_tx_status(dev, &stat);
+
+		cleaned++;
+	}
+	trace_mt_tx_status_cleaned(dev, cleaned);
+
+	spin_lock_irqsave(&dev->tx_lock, flags);
+	if (cleaned)
+		queue_delayed_work(dev->stat_wq, &dev->stat_work,
+				   msecs_to_jiffies(10));
+	else if (test_and_clear_bit(MT7601U_STATE_MORE_STATS, &dev->state))
+		queue_delayed_work(dev->stat_wq, &dev->stat_work,
+				   msecs_to_jiffies(20));
+	else
+		clear_bit(MT7601U_STATE_READING_STATS, &dev->state);
+	spin_unlock_irqrestore(&dev->tx_lock, flags);
+}
+
+int mt7601u_conf_tx(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
+		    u16 queue, const struct ieee80211_tx_queue_params *params)
+{
+	struct mt7601u_dev *dev = hw->priv;
+	u8 cw_min = 5, cw_max = 10, hw_q = q2hwq(queue);
+	u32 val;
+
+	/* TODO: should we do funny things with the parameters?
+	 *	 See what mt7601u_set_default_edca() used to do in init.c.
+	 */
+
+	if (params->cw_min)
+		cw_min = fls(params->cw_min);
+	if (params->cw_max)
+		cw_max = fls(params->cw_max);
+
+	WARN_ON(params->txop > 0xff);
+	WARN_ON(params->aifs > 0xf);
+	WARN_ON(cw_min > 0xf);
+	WARN_ON(cw_max > 0xf);
+
+	val = MT76_SET(MT_EDCA_CFG_AIFSN, params->aifs) |
+	      MT76_SET(MT_EDCA_CFG_CWMIN, cw_min) |
+	      MT76_SET(MT_EDCA_CFG_CWMAX, cw_max);
+	/* TODO: based on user-controlled EnableTxBurst var vendor drv sets
+	 *	 a really long txop on AC0 (see connect.c:2009) but only on
+	 *	 connect? When not connected should be 0.
+	 */
+	if (!hw_q)
+		val |= 0x60;
+	else
+		val |= MT76_SET(MT_EDCA_CFG_TXOP, params->txop);
+	mt76_wr(dev, MT_EDCA_CFG_AC(hw_q), val);
+
+	val = mt76_rr(dev, MT_WMM_TXOP(hw_q));
+	val &= ~(MT_WMM_TXOP_MASK << MT_WMM_TXOP_SHIFT(hw_q));
+	val |= params->txop << MT_WMM_TXOP_SHIFT(hw_q);
+	mt76_wr(dev, MT_WMM_TXOP(hw_q), val);
+
+	val = mt76_rr(dev, MT_WMM_AIFSN);
+	val &= ~(MT_WMM_AIFSN_MASK << MT_WMM_AIFSN_SHIFT(hw_q));
+	val |= params->aifs << MT_WMM_AIFSN_SHIFT(hw_q);
+	mt76_wr(dev, MT_WMM_AIFSN, val);
+
+	val = mt76_rr(dev, MT_WMM_CWMIN);
+	val &= ~(MT_WMM_CWMIN_MASK << MT_WMM_CWMIN_SHIFT(hw_q));
+	val |= cw_min << MT_WMM_CWMIN_SHIFT(hw_q);
+	mt76_wr(dev, MT_WMM_CWMIN, val);
+
+	val = mt76_rr(dev, MT_WMM_CWMAX);
+	val &= ~(MT_WMM_CWMAX_MASK << MT_WMM_CWMAX_SHIFT(hw_q));
+	val |= cw_max << MT_WMM_CWMAX_SHIFT(hw_q);
+	mt76_wr(dev, MT_WMM_CWMAX, val);
+
+	return 0;
+}