linux-kernel - [PATCH v2] mac80211: mesh: Add support for HW RC implementation

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Date:	Thu, 30 Jun 2016 18:30:53 +0300
From:	Maxim Altshul <maxim.altshul@...com>
To:	<linux-kernel@...r.kernel.org>
CC:	Maxim Altshul <maxim.altshul@...com>,
	Johannes Berg <johannes@...solutions.net>,
	"David S. Miller" <davem@...emloft.net>,
	<linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: [PATCH v2] mac80211: mesh: Add support for HW RC implementation

Mesh HWMP module will be able to rely on the HW
RC algorithm if it exists, for path metric calculations.

This allows the metric calculation mechanism to calculate
a correct metric, based on PER and last TX rate both via
HW RC algorithm if it exists or via parameters collected
by the SW.

Signed-off-by: Maxim Altshul <maxim.altshul@...com>
---
Changed the function to return u32, I agree that this
is much clearer.
As for the rate, two things:
1. I had to divide the returned value by 100, since
drv_get_expected_throughput returns values in units of Kbps.
On the contrary, the function cfg80211_calculate_bitrate
returns in units of 100Kbps, so a correction is needed.
2. Why return the value into rate?
As I understand, rate here is actually bitrate,
and so, we have two possible outcomes:
- A SW/HW RC algo does exist, and an estimated throughput is
returned. err is set to 0 (as it is already included in the RC algo)
and the airtime is calculated using the estimated throughput.
- A SW/HW RC algo does not exist, and thus the regular calculation
takes place, in which an estimated throughput is calculated
using the bitrate and the err parameter.
>From this calculation the airtime is calculated.

 net/mac80211/mesh_hwmp.c | 25 +++++++++++++++++--------
 net/mac80211/sta_info.c  | 23 +++++++++++++++++++----
 net/mac80211/sta_info.h  |  2 ++
 3 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index c6be0b4..ad67f46 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -322,19 +322,28 @@ static u32 airtime_link_metric_get(struct ieee80211_local *local,
 	int device_constant = 1 << ARITH_SHIFT;
 	int test_frame_len = TEST_FRAME_LEN << ARITH_SHIFT;
 	int s_unit = 1 << ARITH_SHIFT;
-	int rate, err;
+	int rate = 0, err = 0;
 	u32 tx_time, estimated_retx;
 	u64 result;
 
-	if (sta->mesh->fail_avg >= 100)
-		return MAX_METRIC;
+	/* Try to get rate based on HW/SW RC algorithm.
+	 * Rate is returned in units of Kbps, correct this
+	 * to comply with airtime calculation units
+	 */
+	rate = sta_get_expected_throughput(sta) / 100;
+
+	/* if we did not get a rate */
+	if (!rate) {
+		if (sta->mesh->fail_avg >= 100)
+			return MAX_METRIC;
 
-	sta_set_rate_info_tx(sta, &sta->tx_stats.last_rate, &rinfo);
-	rate = cfg80211_calculate_bitrate(&rinfo);
-	if (WARN_ON(!rate))
-		return MAX_METRIC;
+		sta_set_rate_info_tx(sta, &sta->tx_stats.last_rate, &rinfo);
+		rate = cfg80211_calculate_bitrate(&rinfo);
+		if (WARN_ON(!rate))
+			return MAX_METRIC;
 
-	err = (sta->mesh->fail_avg << ARITH_SHIFT) / 100;
+		err = (sta->mesh->fail_avg << ARITH_SHIFT) / 100;
+	}
 
 	/* bitrate is in units of 100 Kbps, while we need rate in units of
 	 * 1Mbps. This will be corrected on tx_time computation.
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 63ea6cb..fa2c507 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -2069,14 +2069,29 @@ void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo)
 	if (test_sta_flag(sta, WLAN_STA_TDLS_PEER))
 		sinfo->sta_flags.set |= BIT(NL80211_STA_FLAG_TDLS_PEER);
 
+	thr = sta_get_expected_throughput(sta);
+
+	if (thr != 0) {
+		sinfo->filled |= BIT(NL80211_STA_INFO_EXPECTED_THROUGHPUT);
+		sinfo->expected_throughput = thr;
+	}
+}
+
+u32 sta_get_expected_throughput(struct sta_info *sta)
+{
+	struct ieee80211_sub_if_data *sdata = sta->sdata;
+	struct ieee80211_local *local = sdata->local;
+	struct rate_control_ref *ref = NULL;
+	u32 thr = 0;
+
+	if (test_sta_flag(sta, WLAN_STA_RATE_CONTROL))
+		ref = local->rate_ctrl;
+
 	/* check if the driver has a SW RC implementation */
 	if (ref && ref->ops->get_expected_throughput)
 		thr = ref->ops->get_expected_throughput(sta->rate_ctrl_priv);
 	else
 		thr = drv_get_expected_throughput(local, &sta->sta);
 
-	if (thr != 0) {
-		sinfo->filled |= BIT(NL80211_STA_INFO_EXPECTED_THROUGHPUT);
-		sinfo->expected_throughput = thr;
-	}
+	return thr;
 }
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 2cafb21..5c9c8be 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -661,6 +661,8 @@ void sta_set_rate_info_tx(struct sta_info *sta,
 			  struct rate_info *rinfo);
 void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo);
 
+u32 sta_get_expected_throughput(struct sta_info *sta);
+
 void ieee80211_sta_expire(struct ieee80211_sub_if_data *sdata,
 			  unsigned long exp_time);
 u8 sta_info_tx_streams(struct sta_info *sta);
-- 
2.9.0