[PATCH wireless-next 4/8] wifi: rt2800: report the MCS16 to MCS8 fallback of RT3593 in TX status

[Ho Jie Feng <hjf3108@gmail.com>]

The RT3593 retry chain is now MCS 16 to MCS 8, skipping 7 MCS
rates in between. Reflect that in the retry calculation code.

Test results:
   before after
TX 27.0   29.4
RX 70.0   70.0

Signed-off-by: Ho Jie Feng <hjf3108@gmail.com>
---
 drivers/net/wireless/ralink/rt2x00/rt2800lib.c |  8 ++++++++
 drivers/net/wireless/ralink/rt2x00/rt2x00dev.c | 13 +++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
index 9d88ee698b854..de234bcc7a065 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
@@ -1116,6 +1116,14 @@ void rt2800_txdone_entry(struct queue_entry *entry, u32 status, __le32 *txwi,
 		 */
 		__set_bit(TXDONE_SUCCESS, &txdesc.flags);
 		txdesc.retry = ((mcs > real_mcs) ? mcs - real_mcs : 0);
+
+		/*
+		 * On RT3593 MCS16 falls back to MCS8, so a frame that was
+		 * sent below MCS16 after a three stream rate skipped MCS9
+		 * to MCS15.
+		 */
+		if (rt2x00_rt(rt2x00dev, RT3593) && mcs >= 16 && real_mcs < 16)
+			txdesc.retry -= 7;
 	} else {
 		/*
 		 * Transmission failed. The number of retries is
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c b/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c
index 4d94b7062f440..823785088a308 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00dev.c
@@ -329,10 +329,10 @@ static void rt2x00lib_fill_tx_status(struct rt2x00_dev *rt2x00dev,
 	 * lowest rate was used.
 	 */
 	for (i = 0; i < retry_rates && i < IEEE80211_TX_MAX_RATES; i++) {
-		tx_info->status.rates[i].idx = rate_idx - i;
+		tx_info->status.rates[i].idx = rate_idx;
 		tx_info->status.rates[i].flags = rate_flags;
 
-		if (rate_idx - i == 0) {
+		if (rate_idx == 0) {
 			/*
 			 * The lowest rate (index 0) was used until the
 			 * number of max retries was reached.
@@ -340,8 +340,17 @@ static void rt2x00lib_fill_tx_status(struct rt2x00_dev *rt2x00dev,
 			tx_info->status.rates[i].count = retry_rates - i;
 			i++;
 			break;
+		} else if (rate_idx == 16) {
+			/*
+			 * TX_FBK_CFG_3S_0 makes MCS16 fall back to MCS8 on
+			 * RT3593, the decrement below shifts it back to 8.
+			 */
+			if (rt2x00_rt(rt2x00dev, RT3593) &&
+			    (rate_flags & IEEE80211_TX_RC_MCS))
+				rate_idx = 9;
 		}
 		tx_info->status.rates[i].count = 1;
+		rate_idx--;
 	}
 	if (i < (IEEE80211_TX_MAX_RATES - 1))
 		tx_info->status.rates[i].idx = -1; /* terminate */
-- 
2.53.0