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[RFC/RFT] iwlagn: use cts-to-self protection on 5000 adapters series

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This patch fixes 802.11n performance regression I have since 2.6.35. It
boost performance on my 5GHz N-only network from about 5MB/s to 8MB/s.
Similar percentage boost can be observed on 2.4 GHz.

These are results test 5x downloading of approximately 700MB iso image
on wreless-testing kernel:

vanilla: 5.27 5.22 4.94 4.47 5.31 ; avr 5.0420 std 0.35110
patched: 8.07 7.95 8.06 7.99 7.96 ; avr 8.0060 std 0.055946

This was achieved with NetworkManager configured to do not perform
periodical scans, by configuring constant BSSID. With periodical scans,
after some time, performance downgrade to unpached driver level, like
in example below:

patched: 7.40 7.61 4.28 4.37 4.80 avr 5.6920 std 1.6683

However patch still make better here, since similar test on unpached
driver make link disconnects with below messages after some time:

wlan1: authenticate with 00:23:69:35:d1:3f (try 1)
wlan1: authenticate with 00:23:69:35:d1:3f (try 2)
wlan1: authenticate with 00:23:69:35:d1:3f (try 3)
wlan1: authentication with 00:23:69:35:d1:3f timed out

I think patch also helps with

iwlagn 0000:20:00.0: queue 10 stuck 3 time. Fw reload.
iwlagn 0000:20:00.0: On demand firmware reload
iwlagn 0000:20:00.0: Stopping AGG while state not ON or starting

on 2.6.35 kernel, that I can see happens randomly on that version, but
I'm not 100% sure about that.

This is partial revert of:

commit 94597ab23ea10b3bdcba534be00a9f7b35791c07
Author: Johannes Berg <johannes.berg@xxxxxxxxx>
Date:   Mon Aug 9 10:57:02 2010 -0700

    iwlagn: fix rts cts protection

so I'm not sure if patch does not broke things, which that
commit fixes.
---
 drivers/net/wireless/iwlwifi/iwl-5000.c     |    1 -
 drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c |   12 ++----------
 drivers/net/wireless/iwlwifi/iwl-agn-rxon.c |    8 ++++++++
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/net/wireless/iwlwifi/iwl-5000.c b/drivers/net/wireless/iwlwifi/iwl-5000.c
index 98f81df..06949c1 100644
--- a/drivers/net/wireless/iwlwifi/iwl-5000.c
+++ b/drivers/net/wireless/iwlwifi/iwl-5000.c
@@ -433,7 +433,6 @@ static struct iwl_base_params iwl5000_base_params = {
 };
 static struct iwl_ht_params iwl5000_ht_params = {
 	.ht_greenfield_support = true,
-	.use_rts_for_aggregation = true, /* use rts/cts protection */
 };
 
 #define IWL_DEVICE_5000						\
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c b/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c
index b12c72d..23fa93d 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-hcmd.c
@@ -163,17 +163,9 @@ static void iwlagn_tx_cmd_protection(struct iwl_priv *priv,
 				     __le16 fc, __le32 *tx_flags)
 {
 	if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS ||
-	    info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT) {
+	    info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT ||
+	    info->flags & IEEE80211_TX_CTL_AMPDU)
 		*tx_flags |= TX_CMD_FLG_PROT_REQUIRE_MSK;
-		return;
-	}
-
-	if (priv->cfg->ht_params &&
-	    priv->cfg->ht_params->use_rts_for_aggregation &&
-	    info->flags & IEEE80211_TX_CTL_AMPDU) {
-		*tx_flags |= TX_CMD_FLG_PROT_REQUIRE_MSK;
-		return;
-	}
 }
 
 /* Calc max signal level (dBm) among 3 possible receivers */
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn-rxon.c b/drivers/net/wireless/iwlwifi/iwl-agn-rxon.c
index 0238743..96a5832 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn-rxon.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn-rxon.c
@@ -326,6 +326,14 @@ int iwlagn_commit_rxon(struct iwl_priv *priv, struct iwl_rxon_context *ctx)
 			return 0;
 	}
 
+	/*
+	 * force CTS-to-self frames protection if RTS-CTS is not preffered
+	 * one aggregation protection method
+	 */
+	if (!(priv->cfg->ht_params &&
+	      priv->cfg->ht_params->use_rts_for_aggregation))
+		ctx->staging.flags |= RXON_FLG_SELF_CTS_EN;
+
 	if ((ctx->vif && ctx->vif->bss_conf.use_short_slot) ||
 	    !(ctx->staging.flags & RXON_FLG_BAND_24G_MSK))
 		ctx->staging.flags |= RXON_FLG_SHORT_SLOT_MSK;
-- 
1.7.1

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