mac80211: rt2x00: no longer use TXOP_BACKOFF for probe frames

Import a revert-commit from Stanislaw Gruszka which significantly
improves WiFi performance on rt2x00 based hardware.

Signed-off-by: Daniel Golle <[email protected]>

package/kernel/mac80211/Makefile

@@ -11,7 +11,7 @@ include $(INCLUDE_DIR)/kernel.mk
 PKG_NAME:=mac80211
 
 PKG_VERSION:=2017-11-01
-PKG_RELEASE:=8
+PKG_RELEASE:=9
 PKG_SOURCE_URL:=http://mirror2.openwrt.org/sources
 PKG_HASH:=8437ab7886b988c8152e7a4db30b7f41009e49a3b2cb863edd05da1ecd7eb05a
 

package/kernel/mac80211/patches/090-Revert-rt2800-use-TXOP_BACKOFF-for-probe-frames.patch

@@ -0,0 +1,47 @@
+From patchwork Mon May 28 11:25:06 2018
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: Revert "rt2800: use TXOP_BACKOFF for probe frames"
+From: Stanislaw Gruszka <[email protected]>
+X-Patchwork-Id: 10431861
+Message-Id: <[email protected]>
+To: [email protected]
+Date: Mon, 28 May 2018 13:25:06 +0200
+
+This reverts commit fb47ada8dc3c30c8e7b415da155742b49536c61e.
+
+In some situations when we set TXOP_BACKOFF, the probe frame is
+not sent at all. What it worse then sending probe frame as part
+of AMPDU and can degrade 11n performance to 11g rates.
+
+Cc: [email protected]
+Signed-off-by: Stanislaw Gruszka <[email protected]>
+---
+ drivers/net/wireless/ralink/rt2x00/rt2x00queue.c | 7 +++----
+ 1 file changed, 3 insertions(+), 4 deletions(-)
+
+diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00queue.c b/drivers/net/wireless/ralink/rt2x00/rt2x00queue.c
+index a6884e73d2ab..7ddee980048b 100644
+--- a/drivers/net/wireless/ralink/rt2x00/rt2x00queue.c
++++ b/drivers/net/wireless/ralink/rt2x00/rt2x00queue.c
+@@ -372,16 +372,15 @@ static void rt2x00queue_create_tx_descriptor_ht(struct rt2x00_dev *rt2x00dev,
+ 
+ 	/*
+ 	 * Determine IFS values
+-	 * - Use TXOP_BACKOFF for probe and management frames except beacons
++	 * - Use TXOP_BACKOFF for management frames except beacons
+ 	 * - Use TXOP_SIFS for fragment bursts
+ 	 * - Use TXOP_HTTXOP for everything else
+ 	 *
+ 	 * Note: rt2800 devices won't use CTS protection (if used)
+ 	 * for frames not transmitted with TXOP_HTTXOP
+ 	 */
+-	if ((ieee80211_is_mgmt(hdr->frame_control) &&
+-	     !ieee80211_is_beacon(hdr->frame_control)) ||
+-	    (tx_info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE))
++	if (ieee80211_is_mgmt(hdr->frame_control) &&
++	    !ieee80211_is_beacon(hdr->frame_control))
+ 		txdesc->u.ht.txop = TXOP_BACKOFF;
+ 	else if (!(tx_info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT))
+ 		txdesc->u.ht.txop = TXOP_SIFS;