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ath9k_hw: fix PA predistortion miscalibration 

If any bins from the training data are skipped (i != max_index), the
calculated compensation curve gets distorted, and the signal will be
wildly overamplified. This may be the cause of the reported hardware
damage that was caused by PA predistortion (because of which PAPRD was
disabled by default).

When calculating the x_est, Y, theta values, the use of max_index and i
was reversed. i points to the bin index whereas max_index refers to the
index of the calculated arrays.

Note that PA predistortion is still disabled, it will be re-enabled
after it has been properly validated.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Felix Fietkau 2013-05-28 18:04:44 +02:00 committed by John W. Linville
parent b338f74e33
commit 9c8426fc79
1 changed files with 11 additions and 8 deletions
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19
drivers/net/wireless/ath/ath9k/ar9003_paprd.c
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@ -454,6 +454,8 @@ static bool create_pa_curve(u32 *data_L, u32 *data_U, u32 *pa_table, u16 *gain)
if (accum_cnt <= thresh_accum_cnt)
continue;
max_index++;
/* sum(tx amplitude) */
accum_tx = ((data_L[i] >> 16) & 0xffff) |
((data_U[i] & 0x7ff) << 16);
@ -468,20 +470,21 @@ static bool create_pa_curve(u32 *data_L, u32 *data_U, u32 *pa_table, u16 *gain)
accum_tx <<= scale_factor;
accum_rx <<= scale_factor;
x_est[i + 1] = (((accum_tx + accum_cnt) / accum_cnt) + 32) >>
scale_factor;
x_est[max_index] =
(((accum_tx + accum_cnt) / accum_cnt) + 32) >>
scale_factor;
Y[i + 1] = ((((accum_rx + accum_cnt) / accum_cnt) + 32) >>
Y[max_index] =
((((accum_rx + accum_cnt) / accum_cnt) + 32) >>
scale_factor) +
(1 << scale_factor) * max_index + 16;
(1 << scale_factor) * i + 16;
if (accum_ang >= (1 << 26))
accum_ang -= 1 << 27;
theta[i + 1] = ((accum_ang * (1 << scale_factor)) + accum_cnt) /
accum_cnt;
max_index++;
theta[max_index] =
((accum_ang * (1 << scale_factor)) + accum_cnt) /
accum_cnt;
}
/*