2011-09-06 14:49:30

by Rajkumar Manoharan

Subject: [PATCH] ath9k_hw: Fix magnitude/phase average in TxIQ Calibration

The commit "ath9k_hw: Fix Tx IQ Calibration hang issue in
AR9003 chips" did not consider more than one potential sample
while calculating magnitude/phase average if more than one
sample has the same value which could affect post-processing
of outlier detection that causes an undesirable Tx IQ
correction value will be assigned to tx gain settings where
outlier happens.

Cc: Kai Shi <[email protected]>
Reported-by: Paul Stewart <[email protected]>
Signed-off-by: Rajkumar Manoharan <[email protected]>
---
drivers/net/wireless/ath/ath9k/ar9003_calib.c | 17 +++++++++++++----
1 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/ar9003_calib.c b/drivers/net/wireless/ath/ath9k/ar9003_calib.c
index ee3a8a2..6ec3e6d 100644
--- a/drivers/net/wireless/ath/ath9k/ar9003_calib.c
+++ b/drivers/net/wireless/ath/ath9k/ar9003_calib.c
@@ -615,11 +615,10 @@ static void ar9003_hw_detect_outlier(int *mp_coeff, int nmeasurement,
{
int mp_max = -64, max_idx = 0;
int mp_min = 63, min_idx = 0;
- int mp_avg = 0, i, outlier_idx = 0;
+ int mp_avg = 0, i, outlier_idx = 0, mp_count = 0;

/* find min/max mismatch across all calibrated gains */
for (i = 0; i < nmeasurement; i++) {
- mp_avg += mp_coeff[i];
if (mp_coeff[i] > mp_max) {
mp_max = mp_coeff[i];
max_idx = i;
@@ -632,10 +631,20 @@ static void ar9003_hw_detect_outlier(int *mp_coeff, int nmeasurement,
/* find average (exclude max abs value) */
for (i = 0; i < nmeasurement; i++) {
if ((abs(mp_coeff[i]) < abs(mp_max)) ||
- (abs(mp_coeff[i]) < abs(mp_min)))
+ (abs(mp_coeff[i]) < abs(mp_min))) {
mp_avg += mp_coeff[i];
+ mp_count++;
+ }
}
- mp_avg /= (nmeasurement - 1);
+
+ /*
+ * finding mean magnitude/phase if possible, otherwise
+ * just use the last value as the mean
+ */
+ if (mp_count)
+ mp_avg /= mp_count;
+ else
+ mp_avg = mp_coeff[i - 1];

/* detect outlier */
if (abs(mp_max - mp_min) > max_delta) {
--
1.7.6.1

2011-09-06 15:43:46

by Paul Stewart

Subject: Re: [PATCH] ath9k_hw: Fix magnitude/phase average in TxIQ Calibration

Hi Rajkumar,

On Tue, Sep 6, 2011 at 7:50 AM, Rajkumar Manoharan
<[email protected]> wrote:
> The commit "ath9k_hw: Fix Tx IQ Calibration hang issue in
> AR9003 chips" did not consider more than one potential sample
> while calculating magnitude/phase average if more than one
> sample has the same value which could affect post-processing
> of outlier detection that causes an undesirable Tx IQ
> correction value will be assigned to tx gain settings where
> outlier happens.
>
[...]

> + ? ? ? /*
> + ? ? ? ?* finding mean magnitude/phase if possible, otherwise
> + ? ? ? ?* just use the last value as the mean
> + ? ? ? ?*/
> + ? ? ? if (mp_count)
> + ? ? ? ? ? ? ? mp_avg /= mp_count;
> + ? ? ? else
> + ? ? ? ? ? ? ? mp_avg = mp_coeff[i - 1];

Why use "i - 1" here instead of "nmeasurement - 1"? Seems more
error-prone for later changes and harder to understand.

--
Paul