Re: [ 31/78] ath9k: fix max noise floor threshold

[Ben Hutchings]

On Wed, 2012-04-11 at 16:10 -0700, Greg KH wrote:
> 3.3-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx>
> 
> commit 2ee0a07028d2cde6e131b73f029dae2b93c50f3a upstream.
> 
> Currently the maximum noise floor limit is set as too high (-60dB). The
> assumption of having a higher threshold limit is that it would help
> de-sensitize the receiver (reduce phy errors) from continuous
> interference. But when we have a bursty interference where there are
> collisions and then free air time and if the receiver is desensitized too
> much, it will miss the normal packets too. Lets make use of chips
> specific min, nom and max limits always. This patch helps to improve the
> connection stability in congested networks.
[...]

It looks like this is also applicable to 3.0 and 3.2, but the debug
logging statement changed between 3.2 and 3.3 and stopped this from
applying directly.  Attaching an (untested) backport.

Ben.

-- 
Ben Hutchings
It is easier to change the specification to fit the program than vice versa.
From 6d19cb7b3325e6c460db0f07f178793f4500783a Mon Sep 17 00:00:00 2001
From: Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx>
Date: Thu, 15 Mar 2012 06:08:04 +0530
Subject: [PATCH] ath9k: fix max noise floor threshold

commit 2ee0a07028d2cde6e131b73f029dae2b93c50f3a upstream.

Currently the maximum noise floor limit is set as too high (-60dB). The
assumption of having a higher threshold limit is that it would help
de-sensitize the receiver (reduce phy errors) from continuous
interference. But when we have a bursty interference where there are
collisions and then free air time and if the receiver is desensitized too
much, it will miss the normal packets too. Lets make use of chips
specific min, nom and max limits always. This patch helps to improve the
connection stability in congested networks.

Cc: Paul Stewart <pstew@xxxxxxxxxx>
Tested-by: Gary Morain <gmorain@xxxxxxxxxx>
Signed-off-by: Madhan Jaganathan <madhanj@xxxxxxxxxxxxxxxx>
Signed-off-by: Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx>
Signed-off-by: John W. Linville <linville@xxxxxxxxxxxxx>
[bwh: Backported to 3.0/3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/wireless/ath/ath9k/calib.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/calib.c b/drivers/net/wireless/ath/ath9k/calib.c
index 8ddef3e..d771de5 100644
--- a/drivers/net/wireless/ath/ath9k/calib.c
+++ b/drivers/net/wireless/ath/ath9k/calib.c
@@ -20,7 +20,6 @@
 
 /* Common calibration code */
 
-#define ATH9K_NF_TOO_HIGH	-60
 
 static int16_t ath9k_hw_get_nf_hist_mid(int16_t *nfCalBuffer)
 {
@@ -348,10 +347,10 @@ static void ath9k_hw_nf_sanitize(struct ath_hw *ah, s16 *nf)
 			"NF calibrated [%s] [chain %d] is %d\n",
 			(i >= 3 ? "ext" : "ctl"), i % 3, nf[i]);
 
-		if (nf[i] > ATH9K_NF_TOO_HIGH) {
+		if (nf[i] > limit->max) {
 			ath_dbg(common, ATH_DBG_CALIBRATE,
 				"NF[%d] (%d) > MAX (%d), correcting to MAX\n",
-				i, nf[i], ATH9K_NF_TOO_HIGH);
+				i, nf[i], limit->max);
 			nf[i] = limit->max;
 		} else if (nf[i] < limit->min) {
 			ath_dbg(common, ATH_DBG_CALIBRATE,
-- 
1.7.9.5

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